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general description the max11800Cmax11803 low-power touch-screen con- trollers operate from a single supply of 1.70v to 3.6v, tar- geting power-sensitive applications such as handheld equipment. the devices contain a 12-bit sar adc and a multiplexer to interface with a resistive touch-screen panel. a digital serial interface provides communications. the max11800Cmax11803 include digital preprocessing of the touch-screen measurements, reducing bus loading and application-processor resource requirements. the included smart interrupt function generator greatly reduces the frequency of interrupt servicing to the devices. the max11800Cmax11803 enter low-power modes automatically between conversions to save power, making the devices ideal for portable applications. the max11800/max11801 offer two modes of operation: direct and autonomous. direct mode allows the applica- tion processor to control all touch-screen controller activ- ity. autonomous mode allows the max11800/max11801 to control touch-screen activity, thereby freeing the application processor to perform other functions. in autonomous mode, the devices periodically scan the touch screen for touch events without requiring host- processor intervention. this can be used to reduce sys- tem power consumption. an on-chip fifo is used during autonomous mode to store results, increasing effective data throughput and lower system power. the max11800Cmax11803 support data-tagging, which records the type of measurement performed; x, y, z1, or z2, and the type of touch event; initial touch, continuing touch, or touch release. the max11800/max11802 support the spi? serial bus. the max11801/max11803 support the i 2 c serial bus. the max11800Cmax11803 are available in 12-pin tqfn and 12-pin wlp packages, and are specified over the -40c to +85c (extended) and -40c to +105c (auto- motive) temperature ranges. applications features ? 4-wire touch-screen interface ? x/y coordinate and touch pressure measurement ? ratiometric measurement ? 12-bit sar adc ? single 1.7v to 3.6v supply ? two operating modes?irect and autonomous ? data tagging provides measurement and touch event information ? data filtering provides noise reduction ? aperture mode provides spatial filtering ? digital processing reduces bus activity and interrupt generation ? programmable touch-detect pullup resistors ? auto power-down control for low-power operation ? 25mhz spi interface (max11800/max11802) ? 400khz i 2 c interface (max11801/max11803) ? 1.6mm x 2.1mm, 12-pin wlp and 4mm x 4mm, 12-pin tqfn ? low-power operation 343w at v dd = 1.7v, 34.4ksps 888w at v dd = 3.3v, 34.4ksps ? esd protection ?kv hbm ?kv hbm (x+, x-, y+, y-) ?kv cdm ?00v mm max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ________________________________________________________________ maxim integrated products 1 ordering information 19-4711; rev 3; 10/10 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available part temp range pin-package max11800 etc+ -40c to +85c 12 tqfn-ep* max11800gtc/v+ -40c to +105c 12 tqfn-ep* max11800ewc+t -40c to +85c 12 wlp max11801 etc+ -40c to +85c 12 tqfn-ep* max11801gtc/v+ -40c to +105c 12 tqfn-ep* max11801ewc+t -40c to +85c 12 wlp max11802 etc+ -40c to +85c 12 tqfn-ep* max11802ewc+t -40c to +85c 12 wlp max11803 etc+ -40c to +85c 12 tqfn-ep* max11803ewc+t -40c to +85c 12 wlp typical operating circuits and pin configurations appear at end of data sheet. + denotes a lead(pb)-free/rohs-compliant package. /v denotes an automotive qualified part. t = tape and reel. * ep = exposed pad. mobile communication devices pdas, gps receivers, personal navigation devices, media players portable instruments pos terminals handheld games automotive center consoles spi is a trademark of motorola, inc.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 2 _______________________________________________________________________________________ table of contents absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 i 2 c timing characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 spi timing characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 typical operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 functional diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15 detailed description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 position measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 pressure measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 touch-detect modes and options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 pur and puf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 idle modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 features available in the max11800Cmax11803 averaging modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 combined commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 data tagging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 low-power modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 features available in the max11800/max11801 only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 autonomous mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 aperture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 panel setup, measurement, and scan commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 direct conversion mode operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 interrupt modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 panel setup commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 panel measurement commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 combined commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 auxiliary measurement command . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 autonomous conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 measurement operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 combined commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 delayed touch detection during mode transitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 fifo memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 clearing fifo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 fifo data block readback structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 fifo data word structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 block readback operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 clearing interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 aperture modes and options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 aperture range requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 fifo aperture criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 applications information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 using aperture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface _______________________________________________________________________________________ 3 table of contents (continued) examples of using aperture mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 spi communication sequence (max11800/max11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 spi configuration register write (max11800/max11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38 spi configuration or result register read (max11800/max11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39 spi conversion command (max11800/max11802) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 i 2 c-supported sequence (max11801/max11803) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 bit transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 start and stop conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 early stop conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 slave address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 i 2 c register address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 write data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 read data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 streamlined i 2 c read operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 i 2 c conversion and measurement commands (max11801/max11803) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 command and register map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 user-accessible registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45 status and configuration registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 data readback commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 autonomous conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 direct conversion mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 panel setup and measurement commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48 user configuration registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 general status register (0x00) (read only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 general configuration register (0x01) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50 measurement resolution configuration register (0x02) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50 measurement averaging configuration register (0x03) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 adc sampling time configuration register (0x04) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51 panel setup timing configuration register (0x05) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52 delayed conversion configuration register (0x06) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52 touch-detect pullup timing configuration register (0x07) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53 autonomous mode timing configuration register (0x08) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54 aperture configuration register (0x09) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54 auxiliary measurement configuration register (0x0a) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55 operating mode configuration register (0x0b) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56 max11800/max11802 typical operating circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57 max11801/max11803 typical operating circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57 pin configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58 chip information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58 package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 4 _______________________________________________________________________________________ figure 1. i 2 c timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 figure 2. spi timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 figure 3a. max11800/max11801 operation modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 figure 3b. max11802/max11803 operation modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18 figure 4. position measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 figure 5. pressure measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 figure 6. touch-detection circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 figure 7. touch-detection operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 figure 8. state machine transitions (direct conversion mode)max11800Cmax11803 . . . . . . . . . . . . . . . . . . . . .25 figure 9. continuous interrupt mode (direct conversion mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 figure 10. edge interrupt mode (direct conversion mode)max11800Cmax11803 . . . . . . . . . . . . . . . . . . . . . . . .27 figure 11. command and measurement flow (dcm) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 figure 12. panel setup and measurement commandsmax11800Cmax11803 . . . . . . . . . . . . . . . . . . . . . . . . . . .29 figure 13. combined commandsmax11800Cmax11803 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 figure 14. state machine transitionsCCautonomous conversion modemax11800/max11801 . . . . . . . . . . . . . . .31 figure 15. clear-on-read interrupt operationmax11800/max11801 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 figure 16. aperture usage example waveformsmax11800/max11801 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 figure 17. spi single configuration register write sequencemax11800/max11802 . . . . . . . . . . . . . . . . . . . . . .38 figure 18. spi multiple configuration register write sequencemax11800/max11802 . . . . . . . . . . . . . . . . . . . . .38 figure 19. spi single-byte register read sequencemax11800/max11802 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39 figure 20. spi multiple-byte register read sequencemax11800/max11802 . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 figure 21. spi conversion commandmax11800/max11802 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 figure 22. 2-wire interface timing diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 figure 23. start, stop, and repeated start conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 figure 24. acknowledge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41 figure 25. i 2 c single write sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 figure 26. i 2 c multiple write sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42 figure 27. basic single read sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 figure 28. i 2 c multiple read sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 figure 29. i 2 c streamlined read sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44 figure 30. i 2 c conversion and measurement commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 list of figures
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface _______________________________________________________________________________________ 5 list of tables table 1. terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 table 2. operating modes, conditions, and options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 table 3. summary of physical panel settings for supported measurement types . . . . . . . . . . . . . . . . . . . . . . . . . . .20 table 4. median averaging operations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 table 5. data word structure (all direct conversion modes) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 table 6. measurement and event tags (continuous interrupt mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 table 7. measurement and event tags (edge interrupt mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 table 8. panel setup command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 table 9. panel measurement command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 table 10. fifo data block structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 table 11. fifo data word structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 table 12. fifo data measurement tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 table 13. fifo event tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34 table 14. readback and fifo contents with aperture mode enabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 table 15. readback and fifo contents with aperture mode disabled . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 table 16. spi command and data format: 8 bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 table 17. i 2 c command and data format: 8 bits plus ack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46 table 18. status and configuration registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 table 19. data readback command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47 table 20. conversion command summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48 table 21. measurement commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 6 _______________________________________________________________________________________ term definition panel, touch screen, touch panel resistive touch sensor: panel, or touch screen, or touch panel are used interchangeably to denote the resistive touch sensor. tsc touch-screen controller: devices attached to a touch screen that provide the interface between an application processor (ap) and touch screen. x+ x position positive i/o: analog i/o from resistive touch screen. see figure 4 for configuration and measurement details. x- x position negative i/o: analog i/o from resistive touch screen. see figure 4 for configuration and measurement details. y+ y position positive i/o: analog i/o from resistive touch screen. see figure 4 for configuration and measurement details. y- y position negative i/o: analog i/o from resistive touch screen. see figure 4 for configuration and measurement details. r touch touch resistance: represents the resistance between the x and y planes of a resistive touch screen during a touch event. z1 z1 measurement: a resistive touch-screen measurement to determine the resistance between the two planes within the panel sensor during a touch event (r touch ). see figure 5 for configuration and measurement details. z2 z2 measurement: a resistive touch-screen measurement to determine the resistance between the two planes within the panel sensor during a touch event (r touch ). see figure 5 for configuration and measurement details. aux auxiliary input: analog input to the max11800Cmax11803 that can be used to monitor external conditions such as battery voltage or temperature. adc analog-to-digital converter: circuit used to transform analog information into a form suitable for digital operations. ap application processor: an external microcontroller or microprocessor that interfaces to and controls the general operation of the max11 800Cmax11803. avg averaging mode: the ability to average consecutive measurement results to red uce noise from switch bounce, power-supply ripple, and incomplete settling. maf median averaging filter: the maf first removes the minimum and maximum samples before taking the average of the remaining sample set. saf straight averaging filter: the saf takes the average of an entire sample set. tdm touch-detect mode: an untimed mode that monitors the panel for a touch using a user-selectable panel pullup resistor of either 50k or 100k . dcm direct conversion mode: a mode of operation in which the ap requests individual panel setup and conversion operations or automated combinations of measurements (x and y, x and y and z1, or x and y and z1 and z2). the ap maintains control over the initiation of panel setup, measurements, and the sampling f acm autonomous conversion mode: a mode of operation in which the max11800/max11801 idle in tdm until a touch event occurs. after a touch is detected, the max11800/max11801 begin an automated sequence of measurements determined by the user configuration registers. psu panel setup command: user-programmable modes for the purpose of allowing the panel sufficient time to settle, prior to the start of measurements. psu commands configure the on-chip multiplexer in preparation to perform either x, y, z1, or z2 measurements. durations can either be specified and managed by the max11800Cmax11803 (in acm and dcm) or managed by the ap (in dcm). pmc panel measurement command: individual measurements of x or y position and z1 or z2 pressure measurements. cmc combined measurement command: combinations of pmcs (x and y, x and y and z1, or x and y and z1 and z2) offered by the max11800Cmax11803 and executed in series to reduce ap bus and interrupt activity. table 1. terminology
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface _______________________________________________________________________________________ 7 term definition fifo first-in first-out memory: the max11800Cmax11803 contain a 1024-bit fifo that is used to store conversion results when operating in autonomous conversion mode. fifo depth indicates the number of words (16-bit quantity) in the fifo. scan scan: generally, a single sequence of operations performed in dcm or acm. the operations could include a panel setup operation, followed by a panel measurement operation, or a combined measurement operation. scan block scan block: generally, a sequence of multiple operations performed in dcm or acm. the operations could include panel-setup operations, panel-measurement operations, or combined measurement operations. timed scan timed scan: a scan or scan block operation that uses the on-chip oscillator and timer. the timer is controlled through the configuration registers and represents an array of fixed (time) quantities that are user selectable (max11800/max11801). untimed scan untimed scan: a scan or scan block operation that is controlled by the ap. this only applies to dcm. tag d a t a ta g : infor m ati on ap p end ed to the end of an ad c conver si on r esul t. tag s i nd i cate the typ e of m easur em ent and touch status associ ated w i th each p anel ob ser vati on. s ee the d efi ni ti ons for e tag and m tag ( al so i n tab l e 1) . etag event tag: data tags indicating the panel touch status observed during a measurement. mtag measurement tag: data tag indicating the type of measurement read back by the ap (either x, y, z1, or z2). tirq touch interrupt request: active-low interrupt, indicating that a touch is present (cint) or has been initiated (eint) in dcm, or that new data is available in the fifo in acm. eint edge interrupt mode: indicates, through tirq , that a touch has been initiated (eint) in dcm. the duration that tirq is low is user programmable. cint continuous interrupt mode: indicates, through tirq , that a touch is present (cint) in dcm. tirq goes low to indicate the presence of a touch and stays low until the touch event ceases. corint clear-on-read interrupt mode: used in acm only. tirq goes low to indicate the presence of new fifo data. the interrupt is cleared when the data is read by the ap (max11800/max11801). aper aperture mode: available in acm only. reduces data writes to the fifo by spatially filtering measurement data. cont c o n t i n u o u s b i t : an op ti on i n d c m to r etur n the max11800Cmax11803 to a p anel setup ( w ai t) m od e ( p s u ) after a conver si on, r ather than a r etur n to td m ( r ecom m end ed onl y for ap p l i cati ons w i th ver y l ong p anel settl i ng ti m es and r eq uest contr ol l i ng thei r ow n aver ag i ng ) . the conti nuous b i t r esi d es i n b i t 0 ( r0) of the p s u an d p m c r eg i ster s. lpm low-power mode: an idle mode used in dcm/eint or acm modes, when a touch is detected at the conclusion of the last measurement. this indicates a new measurement needs to be requested or scheduled (the touch-detect pullup is not engaged to save power). pur pullup rough: a fast pullup mode, which uses the main x+ switch in parallel with the on-chip resistive pullup (50k/100k ) to quickly slew the touch panel capacitances. r pur 10 typical. puf pullup fine: a slow (fine) pullup mode, which uses the on-chip resistive pullup to slew the touch-panel capacitances to their final values (r puf = 50k or 100k) typical and is required for all applications. sar adc successive approximation register adc: an analog-to-digital converter that converts a continuous analog waveform into a discrete digital representation through a binary search through all possible quantization levels before finally converging upon a digital output for each conversion. i 2 c inter-integrated circuit: a multimaster serial computer bus that is used to attach low-speed peripherals to other components using two bidirectional open-drain lines, serial data (sda) and serial clock (scl), pulled up with resistors. spi serial peripheral interface: a serial interface in which a master device supplies clock pulses to exchange data serially with a slave over two data wires (master-slave and slave-master). table 1. terminology (continued)
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 8 _______________________________________________________________________________________ electrical characteristics (v dd = 1.7v to 3.6v, t a = -40c to +85c (max11800eCmax11803e), t a = -40c to +105c (max11800g/max11801g), unless oth- erwise noted. typical values are at t a = +25c and v dd = 3.3v, unless otherwise noted.) stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v dd to gnd ...........................................................-0.3v to +4.0v x+, x-, y+, y-, aux, tirq to gnd ........................-0.3v to +4.0v scl, clk, sda, din, a0, cs , a1, dout to gnd.-0.3v to +4.0v maximum current into any pin .........................................50ma continuous power dissipation (t a = +70c) 12-pin tqfn (derate 24.4mw/c above +70c) ....1951.2mw 12-pin wlp (derate 6.5mw/c above +70c) ..........518.8mw operating temperature ranges max1180_e_ _..................................................-40c to +85c max1180_g_ _ ...............................................-40c to +105c storage temperature range .............................-65c to +150c junction temperature ......................................................+150c lead temperature (excluding wlp, soldering, 10s) .......+300c soldering temperature (reflow) .......................................+260c parameter symbol conditions min typ max units adc adc resolution no missing codes 10 11 bits differential nonlinearity dnl 12-bit resolution 1.5 lsb integral nonlinearity inl 12-bit resolution 1.5 lsb offset error 2 lsb gain error 4 lsb throughput 105 ksps touch sensors (x+, x-, y+, y-, aux) v dd = 1.7v 7 switch on-resistance v dd = 3.3v 5 switch driver current 100ms pulse 50 ma input voltage range 0 v dd v power supply (v dd ) supply voltage v dd 1.7 3.6 v 1.7v 0.2 power-down mode. all digital inputs static. 3.6v 2 tdm. all digital inputs static. does not include panel currents when touched. 3.6v 7 1.7v 9 timed lpm. all digital inputs static. does not include panel currents when touched. 3.3v 16 1.7v 216 aux conversions at 34.4ksps equivalent rate, spi 3.3v 273 550 1.7v 202 supply current aux conversions at 34.4ksps equivalent rate, i 2 c 3.3v 269 550 a 1.7v 367 aux conversions at 34.4ksps equivalent rate, spi 3.3v 901 1.7v 343 power consumption aux conversions at 34.4ksps equivalent rate, i 2 c 3.3v 888 w absolute maximum ratings note 1: all wlp devices are 100% production tested at t a = +25c. specifications over temperature limits are guaranteed by design and characterization.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface _______________________________________________________________________________________ 9 parameter symbol conditions min typ max units digital inputs (sda, din, scl, clk, a0, cs , a1) input logic-high voltage v ih 0.7 x v dd v input logic-low voltage v il 0.3 x v dd v input leakage current i in v in = 0v or v dd -1 +1 a input hysteresis v hys 0.5 x v dd v input capacitance 6 pf digital outputs (sda, dout, tirq) dout, i source = 1ma 0.9 x v dd output logic-high v oh tirq , cmos configuration, i source = 1ma 0.9 x v dd v output logic-low tirq , dout v ol i sink = 1ma 0.4 v output logic-lowsda v ol i sink = 3ma 0.4 v tirq pullup resistor 125 k electrical characteristics (continued) (v dd = 1.7v to 3.6v, t a = -40c to +85c (max11800eCmax11803e), t a = -40c to +105c (max11800g/max11801g), unless oth- erwise noted. typical values are at t a = +25c and v dd = 3.3v, unless otherwise noted.) i 2 c timing characteristics (v dd = 1.7v to 3.6v, t a = -40c to +85c (max11801e and max11803e), t a = -40c to +105c (max11801g), unless otherwise noted. typical values are at t a = +25c and v dd = 3.3v, unless otherwise noted. see figure 1.) parameter symbol conditions min typ max units serial-clock frequency f scl 0 400 khz bus free time t buf bus free time between stop and start condition 1.3 s hold time for start condition t hd ; sta after this period, the first clock pulse is generated 0.6 s scl pulse-width low t low 1.3 s scl pulse-width high t high 0.6 s setup time for repeated start (sr) condition t su;sta 0.6 s data hold time t hd ; dat 0 900 ns data setup time t su ; dat 100 ns sda and scl rise/fall time t r, t f receiving 20 + c b /10 300 ns sda and scl fall time t tf transmitting 20 + c b /10 250 ns setup time for stop condition t su ; sto 0.6 s v dd = 1.7v to 2.7v 10 100 bus capacitance allowed c b v dd = 2.7v to 3.6v 10 400 pf pulse width of suppressed spike t sp 50 ns
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 10 ______________________________________________________________________________________ spi timing characteristics (v dd = 1.7v to 3.6v, t a = -40c to +85c (max11800e and max11802e), t a = -40c to +105c (max11800g), unless otherwise noted. typical values are at t a = +25c and v dd = 3.3v, unless otherwise noted. see figure 2.) parameter symbol conditions min typ max units clk frequency f clk 25 mhz clk period t cp 40 ns clk pulse-width high t ch 18 ns clk pulse-width low t cl 18 ns cs low to 1st clk rise setup t css0 18 ns cs low after 0th clk rise hold t csh0 to prevent a 0th clk read from being taken as a 1st read in a free-running application 0ns cs high to 17th clk setup t css1 to prevent a 17th clk read from being recognized by the device in a free-running application 18 ns cs high after 16th clk falling edge hold t csh1 0n s cs pulse-width high t csw 18 ns din to clk setup t ds 25 ns din hold after clk t dh 0n s dout transition valid after clk rise t dot output transition time 25 ns dout remains valid after clk rise t doh output hold time 3 ns dout valid before clk rise t do1 t do1 = t cp - t dot 10 ns cs rise to dout disable t dod c load = 20pf 40 ns clk rise to dout enable t doe c load = 20pf. minimum = hold time with regard to 8th clk read. maximum = transition time with regard to 8th clk read. 325ns sda scl s t f t hd;sta t low t r t hd;dat t su;dat t high t f t su;sta t hd;sta sr t sp t buf t su;sto p s figure 1. i 2 c timing diagram
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 11 1 0 89 16 xa6 a5 a4 a3 a2 a1 a0 w d7 d6 d5 d4 d3 d2 d1 d0 din clk cs t csh0 t ds t dh t cl t ch t cp t csw t css1 t sch1 dout high-z spi write operation 1 89 16 x a6 a5 a4 a3 a2 a1 a0 r x x x x x xxx din clk cs t css0 t ds t dh t cl t ch t cp t do0 dout high-z spi read operation t doe t do1 t doh d7 d6 d5 d4 d3 d2 d1 d0 high-z t css0 figure 2. spi timing diagram
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 12 ______________________________________________________________________________________ average supply current vs. sampling rate max11800 toc01 sampling rate (cps) supply current (fa) 180 160 120 140 40 60 80 100 20 10 20 30 40 50 60 70 80 90 0 0 200 autonomous mode max11800 max11801 cps = coordinates per second data taken with resistive touch sensor average supply current vs. sampling rate max11800 toc02 sampling rate (cps) supply current (fa) 180 160 140 120 100 80 60 40 20 1 2 3 4 5 0 0 200 direct continuous interrupt mode cps = coordinates per second average supply current vs. sampling rate max11800 toc03 sampling rate (cps) supply current (fa) 180 160 140 120 100 80 60 40 20 1 2 3 4 5 0 0 200 direct edge interrupt mode cps = coordinates per second supply current in power-down vs. temperature max11800 toc04 temperature (nc) power-down supply current ( a) 60 35 10 -15 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 0.36 0.40 0 -40 85 switch resistance vs. supply voltage max11800 toc05 v dd (v) r on (i) 3.2 2.8 2.4 2.0 4 5 6 y+ 7 8 3 1.6 3.6 x+ y- x- switch resistance vs. temperature max11800 toc06 temperature (nc) r on (i) 60 35 10 -15 2 3 4 5 6 7 1 -40 85 x- x+ y- y+ change in adc gain vs. temperature max11800 toc07 temperature (nc) delta from +25nc (lsb) 80 50 -10 20 -3 -2 -1 0 2 1 3 4 -4 -40 110 change in adc offset vs. temperature max11800 toc08 temperature (nc) delta from +25nc (lsb) 80 50 -10 20 -3 -2 -1 0 2 1 3 4 -4 -40 110 typical operating characteristics (v dd = 1.8v at t a = -40c to +85c (t a = -40c, t a = 0c, t a = +25c, and t a = +85c), 12-bit mode, all measurements using noncontinuous aux input. spi = 10mhz and i 2 c = 400khz, unless otherwise noted. resistive touch-screen panel (x+ to x- = 608 , y+ to y- = 371).)
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 13 average supply current vs. sampling rate max11800 toc09 sampling rate (sps) supply current (fa) 180 160 140 120 100 80 60 40 20 0.5 1.0 1.5 2.0 2.5 3.0 0 0 200 direct conversion mode?auxiliary input sps = samples per second average supply current vs. sampling rate max11800 toc10 equivalent sampling rate (ksps) supply current (fa) 24 16 20 40 60 80 100 120 0 832 auxiliary input data sampled at 1ksps and 2ksps with eight and 16 samples averaging enabled ksps = kilo-samples per second internal oscillator clock frequency vs. temperature max11800 toc11 temperature (nc) internal oscillator clock frequency (mhz) 60 35 10 -15 1.92 1.94 1.96 1.98 2.00 2.02 2.04 2.06 2.08 1.90 -40 85 v dd = 3.6v v dd = 1.8v v dd = 3.0v internal oscillator clock frequency vs. supply voltage max11800 toc12 v dd (v) internal oscillator clock frequency (mhz) 3.0 2.4 1.92 1.94 1.96 1.98 2.00 2.02 2.04 2.06 2.08 1.90 1.8 3.6 power consumption vs. sample rate max11800 toc13 sample rate (cps) power consumption (fw) 150 100 50 20 40 60 80 100 120 140 160 0 0 200 data taken with resistive touch sensor autonomous mode* *max11800/max11801 direct continuous mode direct edge mode cps = coordinates per second typical operating characteristics (continued) (v dd = 1.8v at t a = -40c to +85c (t a = -40c, t a = 0c, t a = +25c, and t a = +85c), 12-bit mode, all measurements using noncontinuous aux input. spi = 10mhz and i 2 c = 400khz, unless otherwise noted. resistive touch-screen panel (x+ to x- = 608, y+ to y- = 371).)
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 14 ______________________________________________________________________________________ pin description pin max11800/max11802 max11801/max11803 tqfn-ep wl p tqfn-ep wl p name function 1 a4 1 a4 x+ x+ channel input/output 2 b4 2 b4 v dd power supply. bypass v dd to gnd with a 1f capacitor. 3 b3 3 b3 gnd ground 4 c4 4 c4 x- x- channel input/output 5 c3 5 c3 y- y- channel input/output 6 c2 6 c2 tirq active-low touch interrupt output 7 c1 - din spi serial data input 8 b1 clk spi serial data clock input 9 a1 cs spi chip-select input 10 b2 dout spi data output 11 a2 11 a2 aux auxiliary input 12 a3 12 a3 y+ y+ channel input/output 7 c1 sda i 2 c serial data bus input/output 8 b1 scl i 2 c serial data clock input 9 a1 a0 i 2 c address input bit 0 10 b2 a1 i 2 c address input bit 1 ep exposed pad (tqfn only). connected to ground.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 15 power and bias y- gnd dout (a1) serial interface physical layer (analog interface) sif phy autonomous mode engine logic core interrupt generation engine sar adc internal clock touch- screen interface mux v dd cs (a0) clk (scl) din (sda) tirq dd v aux x+ x- y+ max11800/max11801 fifo power and bias y- gnd dout (a1) serial interface physical layer (analog interface) sif phy logic core interrupt generation engine sar adc internal clock touch- screen interface mux v dd cs (a0) clk (scl) din (sda) tirq dd v aux x+ x- y+ max11802/max11803 functional diagrams
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 16 ______________________________________________________________________________________ detailed description the max11800Cmax11803 contain standard features found in a typical resistive touch-screen controller as well as advanced features found only on maxim touch- screen controllers. standard features included in the max11800Cmax11803 are: ? 4-wire touch-screen interface ? x/y coordinate measurement ? touch pressure measurement ? direct conversion operationrequires direct ap involvement ? single commandsap initiates all activity, one command at a time ? ratiometric measurement ? 12-bit sar adc ? single 1.7v to 3.6v supply ? programmable touch-detect pullup50k or 100k ? auto power-down control for low-power operation advanced features found in the max11800/max11801 include: ? autonomous conversion operationminimal ap involvement ? on-chip fifobuffers up to 16 consecutive mea- surements ? data taggingrecords measurement and touch- event information ? filteringreduces noise using straight or median averaging ? aperture modeprovides spatial filtering ? combined commandsmultiple operations per- formed with a single ap command ? user-programmable acquisition modes ? programmable interrupt output drive advanced features found in the max11802/max11803 include: ? data taggingrecords measurement and touch event information ? filteringreduces noise using straight or median averaging ? combined commandsmultiple operations per- formed with a single ap command ? user-programmable acquisition modes ? programmable interrupt output drive the max11800/max11801 operate in one of two top- level modes: direct conversion mode (dcm) or autonomous conversion mode (acm). direct conver- sion mode requires the ap to initiate all activity to and from the max11800/max11801. dcm is the operating mode that most standard resistive touch-screen con- trollers use. acm allows the max11800/max11801 to perform measurements automatically and inform the ap when they are complete, reducing data transfers on the serial bus as well as generating fewer interrupt requests. the max11802/max11803 operate in dcm only. dcm requires the ap to initiate all activity to and from the max11802/max11803. dcm is the operating mode that most standard resistive touch-screen con- trollers use. both dcm and acm support averaging, data tagging, and combined commands. certain commands and operations are only available in dcm, while others are only available in acm. see figures 3a and 3b and table 2 for details. position measurements position measurements determine either the x or y coordinates of the point of contact on the panel sensor. allow adequate time for the panel to settle when switch- ing between x and y measurements. figure 4 shows the physical setup of the panel when performing posi- tion measurements. the element r touch represents the resistance between the x and y planes of the panel sensor. r touch does not contribute to the error when performing position measurements. r touch affects the panel settling time required between each valid measurement. the panel end-to-end resistance in the direction of measurement determines the power applied across the panel. the panel dissipates power in the x elements when performing an x direction measurement and dis- sipates power in the y elements when performing a y direction measurement.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 17 direct conversion mode configuration register 0x0b bits[6:5] = 00 panel timing 0x05 panel setup 0x69?0x6f configuration registers setup, measurements, and readback commands panel timing (1) 0x05 n/a configuration registers setup, measurements, and readback commands (2) operation mode autonomous conversion mode configuration register 0x0b bits[6:5] = 01, 10, 11 n/a combined measurement measurement: 0x70?0x75 data readback: 0x52?0x59 combined measurement 0x0b measurement: n/a fifo readback: 0x50 n/a panel measurement measurement: 0x78?0x7f data readback: 0x52?0x59 aux 0x0a aux measurement measurement: 0x76?0x77 data readback: 0x5a?0x5b n/a n/a n/a n/a max11800/max11801 operation modes panel setup averaging method 0x03, 0x0b n/a averaging method (1) 0x03, 0x0b n/a edge interrupt mode 0x01 n/a n/a n/a continuous interrupt mode 0x01 n/a n/a n/a n/a n/a event tag (etag) (fifo not used) data readback: 0x52?0x59 fifo readback: 0x50 fifo readback: 0x50 event tag (etag) (uses fifo) measurement tag (mtag) (fifo not used) data readback: 0x52?0x59 measurement tag (mtag) (uses fifo) clear-on-read interrupt (1) n/a averaging interrupts data tagging n/a n/a aperture setting (1) 0x09, 0x0b n/a aperture n/a n/a adc resolution and timing 0x02, 0x04, 0x06 adc resolution and timing (1) 0x02, 0x04, 0x06 n/a n/a adc pur and puf timing 0x07 pur and puf timing (1) 0x07 n/a n/a tdm timing n/a note 1: the configuration registers must be set up prior to entering autonomous mode. these registers cannot be altered while autonomous mode is active. note 2: commands received while autonomous mode is active are ignored (except readback commands). during autonomous mode all scan activities are controlled by the max11800/max11801, based on the settings of the configuration registers. all measurement results are stored in the on-chip fifo. tint and scanp timing (1) 0x08 n/a n/a autonomous timing measurements tirq tirq 0x01 tirq (1) 0x01 figure 3a. max11800/max11801 operation modes
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 18 ______________________________________________________________________________________ direct conversion mode panel timing 0x05 panel setup 0x69?0x6f configuration registers setup, measurements, and readback commands operation mode n/a combined measurement measurement: 0x70?0x75 data readback: 0x52?0x59 n/a panel measurement measurement: 0x78?0x7f data readback: 0x52?0x59 aux 0x0a aux measurement measurement: 0x76?0x77 data readback: 0x5a?0x5b max11802/max11803 operation modes panel setup averaging method 0x03, 0x0b n/a edge interrupt mode 0x01 n/a continuous interrupt mode 0x01 n/a event tag (etag) (fifo not used) data readback: 0x52?0x59 measurement tag (mtag) (fifo not used) data readback: 0x52?0x59 averaging interrupts data tagging n/a adc resolution and timing 0x02, 0x04, 0x06 n/a adc pur and puf timing 0x07 n/a tdm timing measurements tirq tirq 0x01 figure 3b. max11802/max11803 operation modes
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 19 pressure measurements z1 and z2 measurements determine the resistance between the two planes within the panel sensor during a touch (r touch ). depending on the known physical properties of the panel, one of two equations extract the value of r touch , providing information about the pres- sure and area of the touch applied to the panel. allow adequate time for the panel to settle when switching between position and pressure measurements. figure 5 shows the physical setup of the panel when performing pressure measurements. z1 and z2 measurements allow observation of the volt- age on either side of the effective r touch resistance. with both z1 and z2 measurements available, compute r touch as follows: if only a z1 measurement is available, compute r touch as follows: the power applied across the panel during pressure measurements is greatly dependent on r touch and the physical position of the touch. the maximum power dissipation in the panel during a pressure measurement is approximately p z = v dd 2 /r touch . this maximum r rx touch xplate position n bitx n bi = ? ? ? ? ? ? 2 2 t tz yplate position n bit z r y 1 11 2 ? ? ? ? ? ? ? ?? yy ? ? ? ? ? ? rr xz z touch xplate position n bitx = ? ? ? ? ? ? ? ? ? ? ? ? ? 2 1 2 1 operation mode psu pmc cmc tdm lpm avg fifo aper pur puf cont mtag etag x, y, z1, z2 eint cint cor int dcm max11800C max11803 yes yes yes yes no yes no no yes yes yes 2 yes 2 yes yes yes no acm max11800/ max11801 yes 1 yes 1 yes 1 yes yes yes yes yes yes no yes yes yes no no yes aux no yes 3 no no yes 3 no no no no no no no no no no table 2. operating modes, conditions, and options 1 in acm, the choices are limited to x and y scan, or x and y and z1 scan, or x and y and z1 and z2 scan. 2 in dcm, mtag is always used. for dcm with cont = 0, the following etags are used: 00 = touch present (data valid), 10 = no touch present (data may be invalid), 11 = measurement in progress (data invalid). for dcm with cont = 1, the panel cannot be scanned for a touch because panel setup switches are configured in a measurement mode; therefore, etag = 00 is used if a mea- surement is not in progress, or etag = 11 if a measurement is in progress. 3 a separate configuration register for delay time, sampling time, averaging, and adc resolution settings configures the aux input. r touch x+ y+ y- x- z1 pressure measurement adc input panel r touch v dd x+ y+ y- x- z2 pressure measurement adc input panel v dd figure 5. pressure measurements r touch v dd x+ y+ y- x- x position measurement adc input panel r touch v dd x+ y+ y- x- y position measurement adc input panel figure 4. position measurements
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 20 ______________________________________________________________________________________ power dissipation condition is observed when the point of contact is in the top left corner of the panel sensor. the planar end-to-end resistance included in the cur- rent path is minimal at this location. keep the averaging and panel settling durations to the minimum required by the application when pressure measurements are required. table 3 summarizes the physical panel set- tings for supported measurement types. touch-detect modes and options figure 6 shows the internal circuitry in the max11800Cmax11803 used to detect the presence of a touch on the panel. the selection of the pullup resis- tance value (r td = touch-detect resistance) and the durations of the rough pullup interval (pur = low- impedance pullup) and fine pullup interval (puf = high- impedance pullup) are user-defined. the max11800Cmax11803 revert to the low-power panel setup when placed in touch-detect mode (tdm). figure 6 shows the active panel drive switches (ymsw and xpsw are omitted for simplicity). tsw is a dedicat- ed pullup switch used in tdm. tsw is also used during puf and tdm. xpsw is activated during pur periods. tdrsel allows the selection of an internal pullup resis- tor value of either 50k or 100k. the x and y touch-screen plates create an open circuit with no current flow in the panel when the panel is not being touched. in this case, touch (see figure 6) is low. when a touch causes contact between the panel x and y plates, a current path is created and touch is pulled high, as long as r px + r py (the sum of panel end-to-end resistance) is much lower than r td . typical open-circuit panel plate resistances range from 200 to 1000. the max11800Cmax11803 enter high-impedance pullup mode (50k or 100k ) when the panel is not being touched. the device is idle in this mode until a touch is detected. the ymsw and tsw transistors are on, and the xpsw and psw transistors are off. with no touch present, the y- input of the tsc is at ground and the x+ input is at v dd - v tn , where v tn is the threshold voltage of the tsw nmos device. this is a low-power mode in which no current is consumed until a panel touch occurs. when a touch is present on the panel, the touch-screen controller (tsc) x+ input is pulled low by the touch panel plate resistance and the ymsw tran- sistor. this causes touch to assume a logic-high and the devices either issue the tirq interrupt for direct conversion modes (max11800Cmax11803) or begin self-timed scans for autonomous conversion mode (max11800/max11801). the value of the user-defined r td depends on the characteristics of the panel. to ensure reliable detection values, worst-case panel resistance must be checked against r td . the interaction between r td and the panel (or external noise rejecting) capacitance determines how quickly the panel can be switched from measurement modes back to touch monitoring mode without reporting false touches or erroneous tags due to panel settling. panel touch status is also required to tag data from a completed scan and measurement operation. following each scan operation, the panel must be returned to tdm to determine if the panel is still being touched and if the data obtained during the scan operation should be considered valid. this operation is required since the panel cannot be monitored for the presence of a touch during the scan and measurement procedure. the max11800Cmax11803 must return to tdm after completing a measurement and making a decision on the touch status of the panel. the measurement proce- dure is only completed upon resolution of the touch sta- tus and when data is tagged and available for readback. the characteristics of the return to tdm and mode x+ x- y+ y- ref+ ref- xv dd gnd adc_in u x+ x- y adc_in u v dd gnd y+ y- z1 adc_in gnd v dd uy +x - z2 u gnd v dd adc_in y+ x- pur v dd (10 ) u u gnd u tdm or puf v dd through 50k or 100k u u gnd u l p muuuuu table 3. summary of physical panel settings for supported measurement types note: the adc input is fully differential with the negative input internally connected to gnd. the max11800Cmax11803 control access to the pur, puf, tdm, and lpm, which do not require setup procedures. u indicates unconnected node.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 21 the timing of the decision are configurable through the touch-detect pullup timing configuration register (0x07). program the max11800Cmax11803 in the context of the application to maximize power efficiency and achieve the desired scan throughput. pur and puf pur is a fast pullup mode, which uses the main x+ switch in parallel with the resistive pullup to quickly slew the panel capacitance. puf uses only the touch-detect pullup resistor, r td . pur and puf serve the same func- tion as tdm, but are timed so that the panel can settle after completing measurements and before rendering any decisions on the touch status of the panel. use the optional pur mode to reduce the time to tag data by momentarily placing the panel in a low-imped- ance (< 10 ) pullup mode instead of using the avail- able 50k/100k touch-detection pullup resistors. this operation forces the monitored tsc input high during the pur interval. once the pur interval expires, a puf interval must be allowed so that the panel can recover and pull the tsc input low in case a touch is present. the purpose of the pur mode is to reduce the time required to determine touch status by avoiding long pullup time constants caused by high-capacitance touch panels and the high-impedance on-chip pullup resistors (r td ). when a touch is present during pur intervals, the current through the low-impedance pullup (xpsw) and panel combination is significantly higher than that observed in the puf mode. the durations in the pur mode should be matched to the panel charac- teristics and the desired scan throughput rates to mini- mize power dissipation. while use of the pur mode is optional, the puf period is required for all applications. the puf interval allows the panel to resettle following scan or optional pur intervals. when a touch is not present, the panel capac- itance settles toward v dd through the internal pullup switch and a portion of the panel resistance (with the optional pur mode disabled). when a touch is present, the panel capacitance settles toward ground through a portion of the panel resistance, ideally significantly lower than the selected pullup impedance, r td . allow enough recovery time for settling through the panel resistance when using a pur mode. figure 7 illustrates the touch-detection operations. idle modes once the puf period expires, the preceding measure- ment data is tagged and made available for readback. the max11800Cmax11803 transition to an appropriate mode depending on the conversion and interrupt mode selected. features available in the max11800?ax11803 averaging modes the max11800Cmax11803 contain a programmable averaging filter. when enabled, this feature allows col- lecting 4, 8, or 16 consecutive samples for each mea- surement type requested. the number of the samples for each measurement type is controlled by configura- tion register 0x03. averaging can be assigned to each measurement type. for example, x and y measure- ments can use an average of 16 samples, while z mea- surements can use one or four samples to save power. the aux depth is selected in configuration register 0x0a. the max11800Cmax11803 can be configured to per- form one of two statistical operations. one option is a median averaging filter (maf). the maf first removes the lowest and highest values before averaging the remaining sample set. the second filter type is a straight averaging filter (saf), which takes the average of the entire sample set. both filter types and position/pressure averaging are controlled by configu- ration register 0x0b. table 4 presents the details of the median averaging operations of the max11800C max11803. for the max11800/max11801, averaging is supported in both direct conversion mode and autonomous conversion mode. the max11802/ max11803 support only direct conversion mode. max11800? max11803 pur, puf, tdm pur v dd ymsw xpsw tdrsel psw panel tsw rtd rtd y- x+ pur, puf, tdm (to max11800/ max11801 logic) y+ x- touch figure 6. touch-detection circuitry
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 22 ______________________________________________________________________________________ touch detect pur mode (optional) puf mode scan mode measurement complete? data is known power assisted pullup period (10 ) panel is allowed to resettle before determining data validity is there a touch? yes = lpm. no = tdm. measurement complete? data is known panel is allowed to resettle before determining data validity (through 50k/100k pullup) is there a touch? yes = lpm. no = tdm. data validity is determined (data is tagged) data validity is determined (data is tagged) initial input voltage determined by last scan activity initial input voltage determined by last scan activity forced fast pullup using 10 switch touch not present: tsc input remains high touch present: tsc input pulled low touch not present: tsc input pulled high through 50k/100k pullup touch present: tsc input pulled low by panel time tsc input digital waveform analog waveform time digital waveform analog waveform normal touch detection (note: no pur period; allow long pullup times) fast pullup touch detection (note: increased current in pur mode during touch) v dd tsc input v dd touch detect puf mode scan mode figure 7. touch-detection operations
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 23 combined commands combined commands reduce ap interaction with the max11800Cmax11803 by allowing multiple measure- ments. for example, the max11800Cmax11803 can be instructed to provide x and y data, or x and y and z1 data, or x and y and z1 and z2 data using a single command. data tagging in direct conversion modes, all measurement data is contained in a 16-bit word. x, y, z1, and z2 information is stored independently. each word consists of 12 bits of measurement data plus a 2-bit measurement type (mtag) and a 2-bit event tag (etag). the measure- ment tag identifies whether the data represents an x, y, z1, or z2 result. the event tag indicates the point at which the data is sampled (initial, midpress, or release) during the touch event. when trying to read a result that is pending, the entire data stream is read back as ffffh and the event tag as 11b, indicating that the cor- responding measurement is in progress and that the data stream is to be ignored. for combined commands, all data locations requested by the command are marked ffffh, pending the completion of the entire command and the proper tagging of the data. see table 5. direct conversion modes do not use the internal fifo or support the aperture function (see the aperture modes and options section). each measurement type uses a single location in the (16-bit) memory. the ap must retrieve the data from the last requested measure- ment before moving on to the next measurement of the type. auxiliary measurement data is not tagged because it is not related to panel operation. auxiliary measurement data is stored and read back identically to the other direct conversion data. the tag locations for auxiliary measurement data are always set to 0000b, unless the read occurs when an auxiliary measurement is in progress. in this situation, the tag locations read 1111b and the data stream reads back ffffh. low-power modes there are also two low-power modes, lpm and tdm. lpm only applies when in dcm with edge interrupt mode or acm during periods following a conversion where the panel was observed to be touched and a subsequent panel measurement is required and/or scheduled. during lpm, all circuitry is off, including the on-chip touch-detect pullup resistors used in the touch-detect circuitry. in direct conversion modes, a user-request ini- tiates the next operation and all circuitry is off until a user-command is received. therefore, the current con- sumption is primarily due to junction leakage. in autonomous conversion mode, an on-chip oscillator and timer are constantly running. therefore, the device current consumption is primarily determined by the oscillator and timer. during tdm, all circuitry is off except the on-chip pullup resistor. this is an untimed mode (oscillator and timer are off) for both acm and dcm (no digital current). this mode only consumes current through the on-chip pullup resistor when a touch is present. the device can be powered down through register 0x0b when no panel input is expected or needed, and, therefore, no power is consumed through the panel. index 1514131211109876543210 byte msb byte lsb byte 12-bit content position msbs position lsbs measure event 8-bit content position data trailing zeros* measure event table 5. data word structure (all direct conversion modes) averaging mode number of samples taken number of high samples removed number of low samples removed number of remaining samples averaged 14112 28224 31 64 4 8 table 4. median averaging operations * when using averaging with 8-bit conversions, these positions may be filled with fractional data due to averaging operations.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 24 ______________________________________________________________________________________ features available in the max11800/max11801 only autonomous mode the max11800/max11801 can perform measurements automatically without the ap involvement, and is referred to as autonomous conversion mode (acm). when operating in acm, the max11800/max11801 use an on-chip fifo to store measurement results. as each new data is written to the fifo, an interrupt is generat- ed. the ap can choose to service (read) the fifo result after each interrupt or wait until the fifo is full then read the entire fifo contents at once. the ap can also read the contents of the fifo at any time. see the autonomous conversion mode section for a further description of operations. aperture the max11800/max11801 contain a feature referred to as aperture. it is only available on the max11800/ max11801 when operating in autonomous conversion mode. the aperture feature creates an invisible rectan- gle around a touch location within the max11800/ max11801 hardware. the size of the rectangle is user programmable. one application of the aperture feature is to provide spatial hysteresis. spatial hysteresis can be useful for applications that require lower resolution touch accuracy without requiring the ap to handle the mathematics involved to filter out extraneous data. another application would be to use the aperture fea- ture to implement simple single finger or stylus ges- tures. see the using aperture mode section for a further description of operations. panel setup, measurement, and scan commands to simplify measurement procedures, the max11800C max11803 support three types of commands: panel setup commands (psu), panel measurement commands (pmc), and combined measurement commands (cmc). in direct conversion mode, the max11800/max11801 can use all three types of commands. using individual panel setup and measurement commands allow for a high degree of customization based on decisions made by the ap, while using combined commands signifi- cantly simplifies the complete measurement process and reduces communications between the ap and the max11800Cmax11803. in autonomous mode, the max11800/max11801 use combined commands to control and automate all aspects of panel setup, measurements, and timing. see the operating mode configuration register (0x0b) sec- tion for more details. direct conversion mode operations in direct conversion mode, the ap requests individual panel setup and conversion operations or automated combinations of measurements (x and y, x and y and z1, or x and y and z1 and z2 combined). unlike autonomous conversion modes, the ap maintains control over the initiation of panel setup, measurements events, and the sampling frequency. figure 8 shows the state machine transitions for direct conversion mode. interrupt modes the max11800Cmax11803 support two direct conver- sion interrupt modes. the two direct conversion modes are the continuous interrupt mode (cint) and the edge interrupt mode (eint). continuous interrupt mode in continuous interrupt mode, the panel returns to tdm and idle. the current status of the panel is then sent through tirq. the continuous interrupt mode is the least efficient mode in current consumption for long duration of touches. the power consumption is approxi- mated by p touch = v dd 2 /r pu . the power consump- tion levels observed when the panel is not touched is limited by the junction leakage currents of the max11800Cmax11803. procedure: the max11800Cmax11803 idle in tdm. the tirq output goes low when a touch is detected on the panel indicating to the ap that a touch is present and a measurement operation starts. the ap requests specific panel measurements through the serial interface. tirq stays low during panel setup and measurement operations. once a measurement is complete (with the continuous bit, cont = 0, see table 1), the max11800Cmax11803 check for the con- tinued presence of a touch on the panel and tag the data accordingly (see table 6). the duration of this operation is programmable, specified in the touch-detect pullup timing configuration register (0x07). after the data is tagged, the data is available for readback through the serial interface. the max11800Cmax11803 return to tdm and return control of tirq to the tdm circuitry. tirq stays low while a touch remains present, indicating further measurements are required, otherwise tirq goes high until a new touch is observed. continuous interrupt mode (cint) allows the complete control over the measurement operations and direct obser- vation of the touch status of the panel. figure 9 shows the polling of tirq when other functions share the tirq bus. in the illustration of figure 9, no 10 event tag is observed because the release occurs during a tdm period.
edge interrupt mode when a touch is present on the panel in edge interrupt mode, the max11800Cmax11803 return to an untimed high-impedance mode once data tagging operations are complete. in edge interrupt mode, the duration of a touch is determined by the tags applied to the measurement data. data tagged as initial (00) or midpress (01) indicates the user needs to continue to scan the panel until a release is observed. in this state, there is no need to con- tinue monitoring the touch status prior to the next request- ed measurement. if a panel touch is not present, data is tagged as release (10) and the max11800Cmax11803 idle in tdm continuously, issuing an interrupt only when the next panel touch is initiated. the operation described in the preceding paragraph makes the edge interrupt mode more power-efficient than the continuous interrupt mode. however, the edge interrupt mode requires continuous scanning of the panel until a release (10) event is observed. otherwise, the max11800Cmax11803 do not idle in tdm and are not able to recognize a change in touch status. new touches are not recognized and new interrupts are not issued if a release event is not detected before stop- ping the conversion sequence. max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 25 z1 acquire z2 acquire touch detect touch- detect fine pullup touch- detect fine pullup time is up setup x panel y acquire x detect aux acquire average conversion last conversion not last o r continuous last and not continuous not last or continuous last and not continuous time is up done and continuous done and continuous average conversion last conversion no command no command no command user command internal transition setup y panel setup z panel figure 8. state machine transitions (direct conversion mode)max11800Cmax11803 measurement mtag[3:2] x 00 y 01 z1 10 z2 11 event etag[1:0] touch (data valid) 00 n/a (not used) 01 no touch present (data invalid) 10 measurement in progress (data invalid) 11 table 6. measurement and event tags (continuous interrupt mode)
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 26 ______________________________________________________________________________________ procedure: the eint mode reduces tirq activity. during eint, the max11800Cmax11803 idle in a tdm. tirq goes low when a new touch is detected on the panel. tirq stays low for a fixed duration as specified in the configuration register 0x01, indicating to the ap that a touch is present and measurements are required. the ap requests specific panel setups and measure- ments through the serial interface using panel setup and conversion commands after tirq goes low. once a measurement is complete (with cont = 0), the max11800Cmax11803 check for the continued pres- ence of a touch and tag the data accordingly. see table 7. the duration of this operation is programma- ble, specified in the touch-detect pullup timing configuration register (0x07) section. after the data is tagged, it is available for readback through the serial interface. the max11800Cmax11803 do not return to tdm when the panel touch is still present (etag = 00, 01), but remain in an lpm awaiting further measure- ment commands. the devices return to tdm when the panel touch is no longer present (etag = 10) and return control of the tirq interrupt to the tdm circuitry to await the next touch event. after a touch is indicated, the ap must continue to issue conversion commands until the touch is removed, alert- ing the ap when the panel is released (by etag = 10). the max11800Cmax11803 return to tdm and observe the start of the next touch event. panel commands issued with cont = 1 are not capable of fulfilling this requirement. the eint mode provides the least interrupt activity and the lowest power consumption. use eint mode for general touch-screen applications and applications requiring high resolution in space and time. when the tirq bus is shared with other functions, poll the gener- al status register (0x00) to detect the presence of an interrupt. see figure 10. measurement mtag[3:2] x0 0 y0 1 z1 10 z2 11 event etag[1:0] initial touch (data valid) 00 midpress (data valid) 01 release/no touch present (data invalid) 10 measurement in progress (data invalid) 11 table 7. measurement and event tags (edge interrupt mode) dcm scan etag = 00 dcm scan etag = 00 dcm scan etag = 00 tdm tdm tdm tdm tirq panel touch beginning of touch event end of touch event t ap t sd readback operations are not shown, but are executed during tdm periods. scan interval (t ap ) is controlled by the ap and the initiation of dm scan events. scan duration (t sd ) is a function of the scan type and configuration settings. dcm = direct conversion mode initiated and controlled by the ap figure 9. continuous interrupt mode (direct conversion mode)
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 27 panel setup commands panel setup commands configure the touch panel prior to a measurement. panel setup commands allow the panel to fully settle before performing a measurement. the panel setup command summary is shown in table 8. see the register map in the status and configuration registers section for details on the panel setup timing options for x, y, z1, and z2 measurements. the continuation bit (cont) of the panel setup com- mand programs the max11800Cmax11803 to maintain the present panel setting at the end of the command (cont = 1). panel setup commands assume a logical progression to an appropriate measurement. for exam- ple, when the max11800Cmax11803 are in the x panel setup mode, the devices can proceed to an x measure- ment mode only. the devices return to lpm when an incompatible command follows a panel setup com- mand. see figure 11. for most applications adequate time for panel setup is available as an integral part of the panel measurement commands; configured using the panel setup timing configuration register, 0x05. the dedicated panel setup commands are primarily provid- ed to support applications where the ap needs to con- trol panel setup directly or long panel setup time is required. panel measurement commands a measurement command selects one of the four phys- ical setup options: x, y, z1, or z2. all panel measurement commands include timed inter- vals to power up both the internal adc and the panel with programmable durations. the delayed conversion time (t d_cv , delayed conversion configuration register (0x06)) governs the time that the panel and the adc need to settle prior to the initiations of conversions. the minimum delayed conversion time is 10s, which is the time the internal adc needs to power up. if more set- tling time is required, increase the panel settling time hex access pairable command length operation 0x69h write no 8 x = panel setup 0x6bh write no 8 y = panel setup 0x6dh write no 8 z1 = panel setup 0x6fh write no 8 z2 = panel setup table 8. panel setup command summary dcm scan etag = 10 dcm scan etag = 01 dcm scan etag = 00 tdm lpm lpm tdm tirq panel touch beginning of touch event end of touch event t ap t sd readback operations are not shown, but are executed during tdm periods. tirq duration (t irq ) is specified by the general configuration register (0x01). scan interval (t ap ) is controlled by the ap and the initiation of dm scan events. scan duration (t sd ) is a function of the scan type and configuration settings. t irq initiated and controlled by the ap dcm = direct conversion mode figure 10. edge interrupt mode (direct conversion mode)max11800Cmax11803
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 28 ______________________________________________________________________________________ by delaying the conversion time or by adding an addi- tional panel setup time (t psu ) using the panel setup tim- ing configuration register (0x05). the advantage of using a dedicated panel setup time is that the adc does not consume power during this interval. the required panel setup time is a function of the panel end-to-end resistance, the capacitance of the panel, and any board-level components. when using a measurement command with cont = 1 in a direct conversion mode, the devices remain in the requested setup mode in preparation for the succeeding measurement. the panel does not return to tdm/lpm and the interrupt status is not modified as a result of a measurement command with cont = 1 issued. see figure 12. combined commands in direct conversion modes, the panel returns to a tdm at the conclusion of a combined command and all data are tagged accordingly. the max11800C max11803 then idle in a low-power mode determined by the interrupt mode selected. see figure 13. auxiliary measurement command the max11800Cmax11803 support measurement of an auxiliary input using the internal adc in direct conver- sion mode only. when programmed, the devices sam- ple and quantize the voltage at aux using v dd as the adc reference. the max11800Cmax11803 store the result in the same manner as x, y, z1, and z2 measure- ments, but do not add data tagging. the devices also support averaging functions. auxiliary measurements do not require any panel setup procedure. there is no hex access pairable command length function 0x70h write no 8 x, y = combined command measurement 0x72h write no 8 x, y, z1 = combined command measurement 0x74h write no 8 x, y, z1, z2 = combined command measurement 0x76h write no 8 aux = conversion 0x78h write no 8 x = measurement, cont = 0 0x79h write no 8 x = measurement, cont = 1 0x7ah write no 8 y = measurement, cont = 0 0x7bh write no 8 y = measurement, cont = 1 0x7ch write no 8 z1 = measurement, cont = 0 0x7dh write no 8 z1 = measurement, cont = 1 0x7eh write no 8 z2 = measurement, cont = 0 0x7fh write no 8 z2 = measurement, cont = 1 table 9. panel measurement command summary lpm x psu cmd x meas cmd n y psu cmd y meas cmd z1 psu cmd z1 meas cmd z2 psu cmd z2 meas cmd y n y n y n y n y n y n y n y figure 11. command and measurement flow (dcm)
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 29 panel setup (psu) for x, y, or z drive setting is maintained until next command (cont = 1). panel setup commands (direct conversion only) measurement commands (direct conversion only) single conversion with cont = 1 single conversion with cont = 0 averaged conversion with cont = 0 setup (t psu + t d_cv ) adc acquisition adc conversion adc acquisition i adc conversion i psu data is logged. setting is maintained until next command (cont = 1). averaged conversion with cont = 1 setup (t psu + t d_cv ) psu averaged data is logged. setting is maintained until next command (cont = 1). data is tagged and logged. the max11800?max11803 return to lpm or tdm, according to irq mode. averaged data is tagged and logged. the max11800?max11803 return to lpm or tdm, according to irq mode. n avg n avg setup adc acq adc conv pur (optional) adc acq i adc conv i pur (optional) puf setup puf figure 12. panel setup and measurement commandsmax11800Cmax11803 combined command which includes an auxiliary mea- surement. register 0x0a specifies the configuration for auxiliary measurements. in cint, the max11800Cmax11803 continue to monitor for the touch status of the panel. the devices report any change in touch status in real time during an auxiliary measurement procedure. when performing auxiliary measurements in edge interrupt mode, the max11800Cmax11803 temporarily suspend the panel touch monitoring. the devices noti- fy the ap after the completion of the auxiliary measure- ment when a new touch occurs during the auxiliary measurement.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 30 ______________________________________________________________________________________ x and y commands single conversions data event tagging averaged conversions x psu x acq x conv y psu y acq y conv pur (optional) puf x psu x acq x conv y psu y acq y conv pur (optional) puf x, y, and z1 commands n avgx n avgy single conversions averaged conversions x psu x acq x conv y psu y acq z1 conv pur (optional) puf x psu x acq x conv y psu y acq y conv z1 psu z1 acq y conv z1 psu z1 acq z1 conv pur (optional) puf n avgz1 x, y, z1, and z2 commands single conversions averaged conversions x psu x acq x conv y psu y acq z1 conv pur (optional) puf x psu x acq x conv y psu y acq y conv z1 psu z1 acq y conv z1 psu z1 acq z1 conv z2 conv z2 acq z2 acq z2 conv pur (optional) puf n avgz2 n avgx n avgy n avgz1 n avgx n avgy figure 13. combined commandsmax11800Cmax11803
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 31 x avg done x meas yes no no xyz1 or xyz1z2 mode yes power-down lpm (wait scanp) x psu y avg done y meas yes yes no tag data tdm no touch wait tinit pur puf touch present acm request initial touch touch not present pur puf y psu z2 avg done z2 meas no no xyz1z2 mode z1 avg done z1 meas yes no yes z psu figure 14. state machine transitionsCCautonomous conversion modemax11800/max11801 autonomous conversion mode the max11800/max11801 perform measurements automatically and inform the ap when they are com- plete in autonomous conversion mode, reducing data transfers on the serial bus as well as generating fewer interrupt requests. figure 14 shows the state machine transitions for autonomous conversion mode.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 32 ______________________________________________________________________________________ tdm lpm tdm tirq panel touch end of touch event beginning of touch event t sp t sd lpm interrupt is held pending ap readback (fifo stores data) ap readback, interrupt cleared data written to fifo, interrupt issued t init scan block acm scan etag = 00 acm scan etag = 01 acm scan etag = 10 readback operations are not shown, indicated by the clearing of the ap-initiated interrupt. wait time between touch detection and initial scan (t init ) is specified by configuration settings. scan duration (t sd ) is a function of the scan type and configuration settings. scan period (t sp ) is controlled by configuration settings. acm = autonomous conversion mode figure 15. clear-on-read interrupt operationmax11800/max11801 measurement operations in autonomous conversion, the max11800/max11801 idle in tdm until a touch event occurs. the max11800/max11801 begin an automated sequence of measurements as defined by the configuration regis- ter 0x08h. the max11800/max11801 tag and log the data into the fifo once a measurement is taken. if a touch is still pre- sent, the devices continue to idle in a lpm until the time, as set by the configuration settings, expires. if no touch is present at the expiration of the time set by the configura- tion settings, the max11800/max11801 return to tdm to await the next panel touch. all measurement operations occur without any interven- tion from the ap. the max11800/max11801 issue inter- rupts when new data is available in the internal fifo. the device clears the interrupt when all data is read back. the ap controls the readback of measurement data as the data becomes available. combined commands in autonomous conversion mode, the max11800/ max11801 automatically perform the combined com- mand defined in the configuration register. the devices continuously scan for panel touch events. between scans, the devices idle in a low-power mode according to the present touch status. clear-on-read interrupt mode the max11800/max11801 control the progression through modes in clear-on-read mode. when the panel touch is present, the max11800/max11801 return to a timed high-impedance lpm to minimize current, after the data tagging operations are complete. the max11800/max11801 idle in lpm until it is time to per- form the next required scan, determined by the config- uration register settings. when a touch is not present at the end of a measurement, the device returns to idle in tdm. in tdm, the device waits until a touch is detected before initiating another set of autonomous measure- ments. the max11800/max11801 adopt a clear-on-interrupt protocol (corint) when in autonomous conversion mode. between touch events, the devices idle in a low- power tdm state. upon detection of a touch, the devices begin a sequence of automated measure- ments. each time a qualifying measurement is complet- ed, the data for that measurement is written to the internal fifo. qualifying measurements are measure- ments that indicate the beginning and end of a touch event, which meet aperture requirements (see the aperture range requirements section). tirq issues an interrupt once a qualifying measure- ment is completed and logged into the fifo indicating that new data is available for the ap to read back. the max11800/max11801 continue to perform measure- ments as required by the configuration settings. program the ap to service the interrupt immediately to avoid a fifo overflow and loss of data. tirq remains asserted until all unread fifo data has been read back to the ap. the ap confirms that readback is complete either by monitoring tirq or by monitoring the data event tags embedded in the data for end-of-fifo. (etag = 11b). see figure 15.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 33 delayed touch detection during mode transitions the max11800/max11801 support a low-power power- down mode suspending all touch-screen activity and the panel is not driven. in this mode, the max11800/max11801 is unable to detect a touch. when commanded to transition from pwrdn to any normal mode of operation, the max11800/max11801 go through a pur/puf sequence prior to observing the panel touch status, minimizing the occurrence of inter- rupts issued by false touches caused by the initial state of panel capacitances. in addition, when commanded to transition between normal operating modes, the max11800/max11801 clear any existing interrupts and go through the pur/puf sequence prior to observing the current panel touch status. fifo memory the max11800/max11801 include an internal fifo to store scan block results for readback through the ap. each scan block result contains complete data for all measurements requested by the scan type (x, y; or x, y, z1; or x, y, z1, z2). the depth of each scan data block ranges from 32 bits (x, y mode) to 48 bits (x, y, z1 mode) or 64 bits (x, y, z1, and z2 mode). the internal fifo stores up to 16 complete scan blocks, a total of 1024 bits. regularly service the fifo to prevent overflow conditions. in the event of an over- flow, the fifo ceases to write new data until the old data is read or cleared. avoid overflow to prevent data loss and unreliable behavior. check the general status register (0x00) and the fifo overflow bit to determine if the fifo is in overflow. the fifo overflow bit asserts when a data overflow occurs. see the clearing fifo section. clearing fifo write to the operating mode configuration register (0x0b) to clear the fifo. modifying the contents of the register is not necessary as any write operation to this register location clears the fifo and the interrupt tirq (if present). the fifo completely clears when autonomous conver- sions halt and the max11800/max11801 transition to direct conversion mode. the fifo also clears on transi- tions from direct conversion mode to autonomous mode. fifo data block readback structure table 10 illustrates the scan data block structure within the fifo for each scan type. block boundaries are indi- cated by bold lines. numeric subscripts denote the sample order when the data was taken. readback pro- ceeds from top to bottom. fifo blocks are written as a complete unit with an interrupt issued only after all required block measurements are complete and data is tagged. a fifo data block consists of 2, 3, or 4 fifo data words (word = 16 bits). 2-word block (x, y) 3-word block (x, y, z1) 4-word block (x, y, z1, z2) x 1 msb x 1 msb x 1 msb x 1 lsb x 1 lsb x 1 lsb y 1 msb y 1 msb y 1 msb y 1 lsb y 1 lsb y 1 lsb x 2 msb z1 1 msb z1 1 msb x 2 lsb z1 1 lsb z1 1 lsb y 2 msb x 2 msb z2 1 msb y 2 lsb x 2 lsb z2 1 lsb x 3 msb y 2 msb x 2 msb x 3 lsb y 2 lsb x 2 lsb y 3 msb z2 2 msb y 2 msb y 3 lsb z2 2 lsb y 2 lsb x 4 msb . z1 2 msb x 4 lsb . z1 2 lsb y 4 msb . z2 2 msb y 4 lsb . z2 2 lsb table 10. fifo data block structure
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 34 ______________________________________________________________________________________ fifo data word structure table 11 shows a 16-bit data word (msb byte + lsb byte). each data word consists of 12 bits of position data, mapped to locations [15:4]. eight-bit measure- ment data are left-adjusted and mapped to locations [15:8] and followed by four trailing zeros if averaging is off. if averaging is on, the 4 bits contain random data as a result of the summation and division process. table 12 shows a 2-bit measurement tag indicating the mea- surement type (x, y, z1, or z2), appended in locations [3:2]. table 13 shows a 2-bit event tag indicating where the sample occurs within a touch event (initial, mid- press, or release) in locations [1:0]. all data for a given scan operation is tagged according to the touch status observed at the end of the scan block measurement operations. for example, if a requested x, y, z1, z2 scan block contains a release event, all the data words are tagged 10 before being written to the fifo. an event tag of 11 indicates that the data readback operation reaches the end of the current fifo data log (end of file marker) and there is no unread data in the fifo. terminate the readback operation to await the next interrupt. ignore all data with the 11 event tag. block readback operations the max11800/max11801 do not support partial block readback operations. each readback operation loads an entire scan block result (32, 48, or 64 bits) into a temporary location for serial readback. a scan block is marked as read in the fifo once a scan block result is loaded, freeing the memory space for the subsequent measurements. once initiated, the ap must complete the full readback cycle for the block requested or the unread portions of the block data is lost. clearing interrupt the fifo is only used in the autonomous mode with the clear-on-read interrupt. the interrupt is cleared only when the newest data block currently available in the fifo is loaded for readback. the interrupt does not clear if there is any unread data block remaining in the fifo once a scan block result is loaded. the fifo does not check for partial block readbacks. once the last available fifo data block is loaded for readback, the interrupt clears regardless of whether the readback operation for that block is complete. aperture modes and options the aperture modes available with the max11800/ max11801 implement spatial filtering. the max11800/ max11801 contain the required logic to examine panel measurement data and determine if the data meets the aperture requirements to be written to the fifo. aperture testing decreases the number of entries in the fifo to the minimum required to implement the intended appli- cation. the elimination of extraneous fifo data events reduces activity on the tirq line, serial bus, and mini- mizes ap overhead. the contents in the fifo are not necessarily linearly sampled in time when the device is in aperture mode. aperture range requirements program the aperture range requirements for both x and y through register 0x0b. range requirements are expressed as distance, in position lsbs. the blanking aperture extends from the initial touch position, both x and y with 12-bit resolution (1 lsb = 1/4096 of the corresponding screen dimension). an aperture set- ting of 0x00 effectively disables aperture checking with all measurement data logged to the fifo. apertures are specified in a power-of-two format: x = 2 aprx[3:0]-1 and y = 2 apry[3:0]-1 . event tag[1:0] initial touch 00 midpress 01 release (data invalid) 10 end of file indicator (fifo data invalid) 11 table 13. fifo event tags measurement tag[3:2] x0 0 y0 1 z1 10 z2 11 table 12. fifo data measurement tags index 1514131211109876543210 byte msb byte lsb byte 12-bit content position msbs position lsbs measure event 8-bit content position data trailing zeros* measure event table 11. fifo data word structure * when using averaging with 8-bit conversions, these positions may be filled with fractional data due to averaging operations.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 35 for example: 0000 = 2 -1 lsb = aperture checking disabled 0001 = 2 (1-1) lsb = 1 lsb 0010 = 2 (2-1) lsb = 2 lsb 0011 = 2 (3-1) lsb = 4 lsb 1001 = 2 (9-1) lsb = 256 lsb (1/16 of the touch screen in each direction) 1010 = 2 (10-1) lsb = 512 lsb (1/8 of the touch screen in each direction) 1011 = 2 (11-1) lsb = 1024 lsb (1/4 of the touch screen in each direction) 1100 = 2 (12-1) lsb = 2048 lsb (1/2 of the touch screen in each direction) 1101 to 1111 = aperture checking disabled fifo aperture criteria in autonomous mode with aperture engaged, new data is written to the fifo, and an interrupt is issued when the following conditions occur (aperture mode is not available in direct conversion mode). new panel touch initiated the fifo updates and issues an interrupt when a new touch is observed on the panel (data tag = 00). this event occurs regardless of the current aperture setting and the previous touch location so that multiple presses in the same location can be observed and registered. continuous panel touch terminated the fifo updates and issues an interrupt when a con- tinuous panel touch is terminated (data tag = 10). this event occurs regardless of the current aperture setting and the previous continuous touch location(s) so that multiple presses in the same location can be observed and registered. continuous panel touch measurement meets aperture criteria the max11800/max11801 log the measurement data to the fifo and issue an interrupt when a measurement during a continuous panel touch (event tag = 01) meets the aperture criteria (i.e., lies on or outside the aperture boundary). this event occurs when the point of contact is dragged across the touch screen. only the x or y aperture criteria need to be met and a greater than or equal to qualification criterion is applied. if the change in x position or change in y position exceeds the aper- ture criteria, then an interrupt is generated. applications information using aperture mode aperture mode is only supported in the max11800/ max11801. the max11800/max11801 accommodate touch-panel applications where limited resolution in both time and space can be traded off for reduced microprocessor activity. a simulated keypad is an example of an application where autonomous conver- sion mode with aperture checking could yield an effi- cient solution. the ap determines the durations of touch-screen presses. an issuance of tirq interrupts accompanies all fifo events. the interrupts clear when all existing data is read back by the ap, allowing the ap to correct- ly interpret held panel data. the fifo updates immediately when a new touch event is detected. the system assumes that the panel touch is continuous after the ap receives the interrupt. the max11800/max11801 continue to scan the panel at the user-programmed sample rate. the fifo updates when the measurement data shows that the panel touch loca- tion moves (i.e., a measurement exceeds either of the selected aperture ranges). the fifo also updates upon detection of a panel release. the ap determines the duration of the press by observing the time between the leading edge of the touch (tag 00) and the release edge of the touch (tag 10). all midpress data (tag 01) are inter- preted as part of a dragged touch event. all valid touch events log two data points into the fifo: an initial data point at the beginning of the touch (tag 00) and a release data point at the termination of the touch (tag 10). discard release edge position data as invalid as the max11800/max11801 cannot determine at which point in the adc conversion cycle the panel is released during the measurement operation. if the release occurs while the adc is actively sampling the panel, the results are invalid. only initial and midpress position data are reliable. any touch event too short in duration to log both initial and release data points is recorded in the fifo as a release (tag 10) and discarded as a glitch event. measuring durations of panel touches becomes impractical when the ap services the max11800/ max11801 at lower than the operating speed of the devices and the panel combined. the ap cannot time the duration between panel touches when both the ini- tial and release data points can be logged before the initial interrupt is serviced. do not allow the fifo to overflow as touch information can be lost and the fifo content becomes invalid.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 36 ______________________________________________________________________________________ 0481 21 62 0 4 8 12 16 6 7 24 interrupt timing wavefo rm 1 (assuming frequent servicing events with aperture mode enabled) panel touch spatial waveform one drag event (1:5) and one press event (6:7) interrupt timing waveform 3 (assuming infrequent servicing events) note: position 5 is logged even though position 5 appears in aper4 because position 5 is a release data point. it is the same for position 7. if the position 6 touch event initiates within the final aperture from the previous event (aper4), position 6 is logged as an initial touch event. (1) irq issued (serviced) irq released interrupt timing wavefo rm 2 (assuming frequent servicing events with aperture mode disabled) 1 2 3 45 7 6 1 2 345 7 6 1 2 4 5 3 initial touch initial release second release second touch drag drag drag drag aper6 aper4 aper3 aper2 aper1 tirq tirq tirq figure 16. aperture usage example waveformsmax11800/max11801 when the max11800/max11801 operate in autonomous conversion mode with low or no aperture ranges, the fifo and interrupt activity occur frequently with the ap servicing the devices frequently to avoid loss of data due to limited fifo depth. for this reason, do not per- form autonomous conversion for applications where a high resolution in either space or time is required. use direct conversion mode when requiring a high resolu- tion in either space or time. examples of using aperture mode figure 16 shows an example of a touch sequence. a dragged touch sequence is initiated at position 1 and continues through to position 5. while multiple samples are taken during this sequence, only those samples that meet aperture requirements are enumerated and are shown with the corresponding aperture ranges. positions 6 and 7 show a subsequent momentary press event. figure 16 shows the anticipated interrupt waveforms in several operating modes. the first waveform shows interrupt operation assuming that aperture mode is enabled (with x = y = 4 lsbs), assuming that the ap service interrupts at a frequency faster than the select- ed tsc sample rate. each qualifying sample induces a fifo event and an interrupt pulse as shown. timing between fifo events can be timed by the ap to deter- mine duration information. table 14 shows the read- back data assuming that the fifo does not fill up.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 37 sample x y tag comment 1 7 11 00 initial event (beginning of first touch) 1a 9 10 01 midpress event 2 11 9 01 midpress event 2a 12 8 01 midpress event 2b 13 7 01 midpress event 2c 13 6 01 midpress event 3 13 5 01 midpress event 3a 15 6 01 midpress event 4 17 7 01 midpress event (last valid position data) 5 19 6 10 release event (end of first touch, ignore position data) 6 22 14 00 initial event (beginning of second touch) 7 23 15 10 release event (end of second touch, ignore position data) table 15. readback and fifo contents with aperture mode disabled sample x y tag comment 1 7 11 00 initial event (beginning of first touch) 2 11 9 01 midpress event 3 13 5 01 midpress event 4 17 7 01 midpress event (last valid position data) 5 19 6 10 release event (end of first touch, ignore position data) 6 22 14 00 initial event (beginning of second touch) 7 23 15 10 release event (end of second touch, ignore position data) table 14. readback and fifo contents with aperture mode enabled the second waveform shows an interrupt operation assuming that aperture mode is disabled (or that x = y = 0 lsb), assuming that the ap service interrupts at a frequency faster than the selected tsc sample rate. every sample induces a fifo event and an interrupt pulse as shown. the interrupt waveform is significantly busier than that shown in the first waveform. duration information can now be directly determined from the fifo samples since each sample is logged and occurs at the programmed sample rate. table 15 lists the read- back data assuming the fifo does not fill up. the third waveform in figure 16 shows an interrupt oper- ation assuming that the max11800/max11801 are infre- quently serviced. ensure that the fifo does not overflow. no duration information is available at resolutions below the servicing rate. either the set of data shown in table 14 or the set shown in table 15 appears in the fifo when read, depending on the aperture setting.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 38 ______________________________________________________________________________________ cs sclk din a n [6:0] 1 9 17 25 32 7 23 d n [7:0] a m [6:0] d m [7:0] figure 18. spi multiple configuration register write sequencemax11800/max11802 spi communication sequence (max11800/max11802) the spi interface consists of three inputs, din, dclk, cs, and one output, dout. a logic-high on cs dis- ables the max11800/max11802 digital interface and places dout in a high-impedance state. pulling cs low enables the max11800/max11802 digital interface. the max11800/max11802 provide two possible implemen- tations of spi instructions. in rising-edge-driven opera- tions, the devices are able to run at maximum clock speeds. carefully consider the hold time requirements of the max11800/max11802 and minimize board skew contributions when running the max11800/max11802 at maximum clock speed. in falling-edge-driven opera- tions, the device is less sensitive to board skew contri- butions, but slower clock speeds are required to meet the max11800/max11802 setup time requirements. for the max11800/max11802, read patterns output data is either latched on the rising edge running at maximum clock rates or on the falling edges running at reduced clock rates. spi configuration register write (max11800/max11802) figure 17 shows the supported write operation sequence for the max11800/max11802. a single con- figuration register can be written in a 2-byte operation, composed of a target register address (a[6:0], plus a write mode indicator bit) followed by data to be written to the target register (d[7:0]). during write sequences, the dout line is not accessed by the spi. dout remains high impedance throughout the command. using the optional bus holder, the dout line retains the previous value unless altered by a device sharing the bus. the max11800/max11802 spi interface supports multi- ple register write operations within a single sequence as shown in figure 18. by repeating the address plus data byte pairs (in write mode), an unlimited number of registers can be written in a single transfer. do not per- mit to combine write and read operations within the same spi sequence. cs sclk din 16 12 3 4 56 78 9101112131415 a6 a5 a4 a3 a2 a1 w a0 d6 d5 d4 d3 d2 d1 d0 d7 figure 17. spi single configuration register write sequencemax11800/max11802
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 39 spi configuration or result register read (max11800/max11802) figure 19 shows the read operation sequence for the max11800/max11802. a single configuration register can be read back in a 2-byte operation, composed of a requested register address (a[6:0], plus a read mode indicator bit) followed by the data contents from that reg- ister (d[7:0]). during read operations, the spi takes control of the dout line following the eight sclk rising edge. the spi retains control of the dout line until cs rises, terminating the operation. to support multiple register readback opera- tions, data continues to be ported following the 16th rising clock edge. for single-byte transfers, this sub-bit informa- tion can be ignored, shown as s, in figure 19. the dout output on the max11800/max11802 includes an optional bus holder to prevent the dout line from maintaining an indeterminate state when vacated by the device in the absence of an external bus pullup or bus sharing devices. the bus holder is designed not to inter- fere with other drivers sharing the dout line and holds the last valid state of the line, regardless of source. disable the bus holder when not needed. the max11800/max11802 support the combination of the din and dout lines. to avoid data contention and possible high current states, the master device must relin- quish control of the combined line at the 8th clock rising edge, allowing the max11800/max11802 to access the line through the end of the sequence. this is terminated on the rising edge of cs. see the spi timing characteristics for relevant details. the max11800/max11802 also support multiple register readback operations using a single command. the proto- col requires the user to supply an initial starting register location, followed by an unlimited number of clock pulses for data readback. the first data read back is from the start register. the max11800/max11802 internal autoincrement counter manages the data readback in later cycles. if autoin- crement is supported, the next register location is read back. if not, the last valid register location is read back (see the command and register map section for the autoincrement attributes of each register). the following example shows a valid sequence for the readback of three register locations (d i through d i+2 ). the autoincrement reads only the x, y, z1, z2, and aux result registers preventing inadvertent readback of unre- lated or reserved data locations. for example, if begin- ning at the xmsb register, a user can cycle through the xlsb register to the ymsb register and so forth up to the auxlsb register. the max11800/max11802 do not autoincrement beyond the auxlsb register. if clock cycles continue to be given, the auxlsb register read- back is repeated. the fifo register does not autoincrement, which allows multiple readbacks of the same location. this allows the access of multiple fifo memory blocks with a single read operation. when reading back fifo registers, data man- agement is handled in blocks not bytes. as a result, when an spi read operation supplies at least one cycle of read- back of the first byte of a fifo block, the entire block is marked as read, regardless of whether the block or even byte readback is run to completion. to illustrate, assume the max11800 is in autonomous mode performing xy conversions and a fifo readback is requested starting at register 0x50. clock cycles 9 to 40 are required to complete the readback of the first available fifo block i = {xmsb i , xlsb i , ymsb i , ylsb i } with the device updating in response to the 8th to 39th clock rising edges. the host processor can complete the readback data latching of ylsb i [0] either on the 39th falling edge or the 40th rising edge. to support a continued readback of further fifo blocks, the device updates the dout line to xmsb i+1 [7] in response to the 40th clock rising edge (though block i+1 is not marked as read). if the ap supplies a 42nd clock rising edge, the fifo block i+1 , if present, is marked as read, regard- less of whether any further clock cycles are provided. cs sclk din 16 1 2 3 4 5 6 7 8 910 1112131415 a6 a5 a4 a3 a2 a1 r a0 d6 d5 d4 d3 d2 d1 d0 d7 dout s figure 19. spi single-byte register read sequencemax11800/max11802
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 40 ______________________________________________________________________________________ spi conversion command (max11800/max11802) the sequence in figures 20 and 21 shows the required command format for issuing conversion requests. a conversion request cannot be paired with multiple com- mands or instructions. any conversion command issued while previous commands are being executed is ignored. i 2 c-supported sequence (max11801/max11803) the max11801/max11803 feature an i 2 c/smbus?- compatible, 2-wire serial interface consisting of a serial- data line (sda) and a serial-clock line (scl). sda and scl facilitate communication between the max11801/max11803 and the master at clock rates up to 400khz. figure 22 shows the 2-wire interface timing diagram. the master generates scl and initiates data transfer on the bus. the master device writes data to the max11801/ max11803 by transmitting the proper slave address fol- lowed by the register address and then the data word. each transmit sequence is framed by a start (s) or repeated start (sr) condition and a stop (p) condi- tion. each word transmitted to the max11801/ max11803 is 8 bits long and is followed by an acknowl- edge clock pulse. a master reading data from the max11801/max11803 transmits the proper slave address followed by a series of nine scl pulses. the max11801/max11803 trans- mits data on sda in sync with the master-generated scl pulses. the master acknowledges receipt of each byte of data. each read sequence is framed by a start (s) or repeated start (sr) condition, a not- acknowledge, and a stop (p) condition. sda operates as both an input and an open-drain output. a pullup resistor, typically greater than 500 , is required on sda. scl operates only as an input. a pullup resistor, typically greater than 500, is required on scl if there are multiple masters on the bus, or if the single master has an open-drain scl output. series resistors in line with sda and scl are optional. series resistors protect the digital inputs of the max11801/max11803 from high-voltage spikes on the bus lines and minimize crosstalk and undershoot of the bus signals. bit transfer one data bit is transferred during each scl cycle. the data on sda must remain stable during the high period of the scl pulse. changes in sda while scl is high are control signals (see the start and stop conditions section). start and stop conditions sda and scl idle high when the bus is not in use. a master initiates communication by issuing a start condition. a start condition is a high-to-low transition cs sclk din 12345678 a6 a5 a4 a3 a2 a1 w a0 figure 21. spi conversion commandmax11800/max11802 cs sclk din a i [6:0] 1 9 17 25 32 724 16 dout 8 s d i [7:0] d i+1 [7:0] d i+2 [7:0] figure 20. spi multiple-byte register read sequencemax11800/max11802 smbus is a trademark of intel corp.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 41 on sda with scl high. a stop condition is a low-to- high transition on sda while scl is high (figure 23). a start condition from the master signals the beginning of a transmission to the max11801/max11803. the master terminates transmission and frees the bus by issuing a stop condition. the bus remains active if a repeated start condition is generated instead of a stop condition. early stop conditions the max11801/max11803 recognize a stop condition at any point during data transmission, except if the stop condition occurs in the same high pulse as a start condition. for proper operation, do not send a stop condition during the same scl high pulse as the start condition. slave address the slave address is defined as the seven most signifi- cant bits (msbs) followed by the read/write bit (r/ w ). for the max11801/max11803 the seven most significant bits are 10010 a1 a0, where a1 and a0 are user config- urable through the address input pins a1 and a0. the lsb is the read/write bit. setting the r/ w bit to 1 config- ures the max11801/max11803 for read mode. setting the r/w bit to 0 configures the max11801/max11803 for write mode. the address is the first byte of informa- tion sent to the max11801/max11803 after the start condition. see figures 25 and 26 for details. i 2 c slave address = 1 0 0 1 0 a1 a0 r/w i 2 c register address the register addresses are defined as the seven most significant bits (msbs) followed by a dont care bit. the format is n n n n n n n x, where n is the register address and x is a dont care. acknowledge the acknowledge bit (ack) is a clocked 9th bit that the max11801/max11803 use to handshake receipt each byte of data when in write mode (see figure 24). the max11801/max11803 pull down sda during the entire 128 9 start condition scl sda acknowledge not acknowledge clock pulse for acknowledgement figure 24. acknowledge scl sda ssrp figure 23. start, stop, and repeated start conditions figure 22. 2-wire interface timing diagram sda scl s t f t hd;sta t low t r t hd;dat t su;dat t high t f t su;sta t hd;sta sr t sp t buf t su;sto p s
max11800?ax11803 master-generated 9th clock pulse if the previous byte is successfully received. monitoring ack allows for detec- tion of unsuccessful data transfers. an unsuccessful data transfer occurs if a receiving device is busy or if a system fault has occurred. in the event of an unsuc- cessful data transfer, the bus master retries communica- tion. the master pulls down sda during the 9th clock cycle to acknowledge receipt of data when the max11801/max11803 are in read mode. an acknowl- edge is sent by the master after each read byte to allow data transfer to continue. a not-acknowledge is sent when the master reads the final byte of data from the max11801/max11803, followed by a stop condition. write data format a minimum write sequence to the max11801/ max11803 includes transmission of a start condition, the slave address with the r/ w bit set to 0, 1 byte of data to select the internal register address pointer, 1 byte of data written to the selected register, and a stop condition. figure 25 illustrates the proper frame format for writing 1 byte of data to the max11801/ max11803. figure 26 illustrates the frame format for writing n-bytes of data to the max11801/max11803. the slave address with the r/w bit set to 0 indicates that the master intends to write data to the max11801/max11803. the max11801/max11803 acknowledge receipt of the address byte during the master-generated 9th scl pulse. the second byte transmitted from the master config- ures the max11801/max11803s internal register address pointer. the pointer tells the max11801/ max11803 where to write the next byte of data. note that the max11801/max11803 use a 7-bit register pointer format, and the selection should be left-justified within the register byte (the last bit in the register byte is a dont care). an acknowledge pulse is sent by the max11801/max11803 upon receipt of the address pointer data. the third byte sent to the max11801/max11803 contains the data that is written to the chosen register. an acknowledge pulse from the max11801/max11803 sig- nals receipt of the data byte. the max11801/ max11803 do not support autoincrement in write mode. however, by repeating multiple register address byte + data byte pairs (bytes 2 and 3 in figure 25) the user can perform multiple register writes within a single transfer. there is no limit as to how many registers the user can write with a single command sequence, but only commands listed as ?airable?can be sequenced in this manner. for example, the i 2 c master can perform multiple register writes to set up all required conversion options and then issue a separate i 2 c com- mand to start a conversion process. figure 26 illustrates how to write to multiple registers with one frame. the master signals the end of transmission by issuing a stop condition. register addresses greater than 0x0b are reserved. do not write to these addresses. low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 42 ______________________________________________________________________________________ start write address byte 1: device address write register number byte 2: reg number = n write data byte 3: reg(n)[7:0] data stop w n3 n2 n1 n0 x d d d d d d d d n4 1 0 0 1 0 a1 a0 n5 n6 z z z z x d d d d d d d d z z z write data byte 5: reg(z)[7:0] data write register number byte 4: reg number = z sda scl a a aa a acknowledge generated by i 2 c master acknowledge generated by max11801/max11803 figure 26. i 2 c multiple write sequence scl w n3 n2 n1 n0 x d d d d d d d d start sda write address byte 1: device address write register number byte 2: first reg number = n write data byte 3: reg(n)[7:0] data stop n4 1 0 0 1 0 a1 a0 n5 n6 aa a acknowledge generated by i 2 c master acknowledge generated by max11801/max11803 figure 25. i 2 c single write sequence
read data format send the slave address with the r/w bit set to 1 to initi- ate a read operation. the max11801/max11803 acknowledge receipt of its slave address by pulling sda low during the 9th scl clock pulse. transmitted data is valid on the rising edge of scl. a stop condi- tion can be issued after any number of read data bytes. the address pointer should be preset to a specific reg- ister before a read command is issued. the master pre- sets the address pointer by first sending the max11801/max11803s slave address with the r/ w bit set to 0 followed by the selected register address. a repeated start condition is then sent followed by the slave address with the r/ w bit set to 1. the max11801/ max11803 then transmit the contents of the selected register. if the selected register supports autoincrement, the register pointer automatically increments after trans- mitting each data byte, making data in the next register location available for access in the same transfer. some registers do not support autoincrement, usually because they are at the end of a functional section or, in the case of the fifo, store multiple records. the master acknowledges receipt of each data byte received from the max11801/max11803 during the acknowledge clock period. if the master requires more data from the max11801/max11803, it brings the acknowledge line low, indicating more data is expect- ed. this sequence is repeated until the master termi- nates with a not-acknowledge (~a) followed by a stop condition. figure 27 illustrates the frame format for max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 43 start write address byte 1: device address write register start number byte 2: first reg number = n stop w n3 n2 n1 n0 x d d d d d d d d read data byte 4: reg(n)[7:0] data repeated start additonal sequential read data bytes read data d d d d d d d~a d read data (last byte) r write address byte 3: device address acknowledge generated by i 2 c master acknowledge generated by max11801/max11803 n4 n5 n6 1 0 0 1 0 a1 a0 1 0 0 1 0 a1 a0 sda scl aa a a a = acknowledge ~a = not acknowledge figure 28. i 2 c multiple read sequence sda sda direction scl 1 0 0 1 0 a1 a0 w n6 n5 n4 n3 n2 n1 n0 x ack ack out in out into max11801/max11803 sda (cont.) scl (cont.) 0 a1 d7 d6 d5 d4 d3 d2 d1 d0 ack out a0 in in start 1 0 0 1 r sr stop nack start write address byte 1: device address write register start number byte 2: first reg number = n stop read data byte 4: reg(n)[7:0] data repeated start write address byte 3: device address acknowledge generated by i 2 c master acknowledge generated by max11801/max11803 a = acknowledge ~a = not acknowledge 1 sda scl 0 0 1 0 a1 n6 n5 n4 n3 n2 n1 n0 1 0 0 1 0 a1 ad d d d d d d d ~a ra2 x a a2 aw figure 27. basic single read sequence
max11800?ax11803 reading one byte from the max11801/max11803. figure 28 illustrates the frame format for reading multi- ple bytes from the max11801/max11803. as previously indicated, the max11801/max11803 read sequence does not limit how many bytes one can read. where allowed, the internal register counter keeps incrementing as additional bytes are requested, the first byte out is reg(n), next byte out is reg(n+1), next byte out is reg(n+2), and so on. the user needs to track the incremented register address. acknowledge pulses from the master are not required to autoincrement the internal register loca- tion; the internal register location updates on each byte. see the register map for details governing the incrementing of register addresses. some registers autoincrement only up to a point (for example, the x, y, z1, z2, and aux result registers). this is to prevent inadvertent readback of unrelated or reserved data locations. for example, if beginning at the xmsb register, a user can cycle through the xlsb register to the ymsb register and so forth up to the auxlsb register. the max11801/max11803 do not autoincrement beyond the auxlsb register; if bytes continue to be given, the auxlsb register readback is repeated. some registers do not autoincrement (for example, the fifo register). this is intentional as it allows multiple readbacks of the same location (in this case, allowing the user to access multiple fifo memory blocks with a single read operation). note that when reading back fifo registers, data management is handled in blocks (not bytes); thus, if an i 2 c read operation sup- plies at least one cycle for readback of the first byte of a fifo block, the entire block is marked as read (regardless of whether the block or even byte read back is run to completion). streamlined i 2 c read operations the max11801/max11803 support several streamlined readback behaviors for several commands to signifi- cantly improve data transfer efficiency. resumed read operations the max11801/max11803 internal address pointer autoincrements after each read data byte. this autoin- crement feature allows all registers to be read sequen- tially within one continuous frame. a stop condition can be issued after any number of read data bytes. if a readback sequence is stopped, readback can later be resumed from the current (autoincremented) register location; it is not necessary to supply the initial register address and register selection sequence. users can simply begin with a start followed by the device slave address with r/w set high. following the acknowledge, data readback commences from the previous register address (next register address after the first one is suc- cessfully read). this sequence is designated as a streamlined sequence and is shown in figure 29. resumed read operation of the fifo register (max11801) if the user accesses the fifo register (the fifo does not autoincrement) and reads several conversion results and then stops, when returning for more fifo data it is only necessary to simply issue the streamlined readback sequence to continue to gather results from the fifo. thus, once the max11801 is placed in autonomous conversion mode, the user needs only issue the full readback sequence once for the initial fifo access. from this point on, streamlined read access to the part resumes at the next available fifo location (unless an intervening command is issued to modify the devices register address pointer). resumed read operation of the results registers (max11801/max11803) likewise, if a user is reading back result registers, the user can begin with xmsb and autoincrement to xlsb, and then stop. if the user resumes by simply issuing the streamlined readback sequence, data readback com- mences from the ymsb location. this behavior remains valid unless another direct conversion or configuration command has been issued (see next). low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 44 ______________________________________________________________________________________ start write address byte 3: device address d d d d d d d d read data byte 4: reg(n)[7:0] data additonal sequential read data bytes read data stop d d d d d d d~a d read data (last byte) r acknowledge generated by i 2 c master acknowledge generated by max11801/max11803 1 0 0 1 0 a1 a0 sda scl a a a = acknowledge ~a = not acknowledge figure 29. i 2 c streamlined read sequence
direct conversion read operations all direct conversion commands automatically set the readback target register, streamlining data gathering operations. see the register map for specific details for all such commands. for example, if the user writes a command requesting an xy combined measurement, the max11801/max11803 automatically set the default readback register pointer to the xmsb location. thus, if the xy command is issued and allowed to complete, it can then be followed directly by a streamlined read sequence of the format, as shown in figure 29, and newly acquired data is read back, commencing with the xmsb register. note that accepted direct conversion commands always modify the current internal register location and effectively override the resumed readback behaviors and any register settings made in response to previous- ly completed direct conversion commands. users wish- ing to override this behavior can use still use the standard readback sequences of the format, as shown in figures 28 and 29. read operations following write operations if the streamlined readback sequence is issued follow- ing a configuration write operation, data readback com- mences from the last written register location. thus, if the user modifies the contents of the operating mode configuration register (0x0b) using a write sequence and then issues a streamlined readback sequence, the contents of register 0x0b are provided. note that register write operations always modify the current internal register location and effectively override the resumed readback behaviors. i 2 c conversion and measurement commands (max11801/max11803) figure 30 shows the required command format for issuing conversion and measurement requests. a request cannot be paired with multiple commands or instructions. any command issued while previous com- mands are being executed is ignored and the read- back target register is not modified. command and register map the command map consists of the user-configuration reg- isters (read/write), tsc data readback commands (read only), and tsc panel setup and conversion commands (write only). user-accessible registers there are six blocks of user-accessible registers and commands that control all operations of the max11800Cmax11803. the register blocks and com- mands consist of the following: 1) status and configuration registers: 00h to 0bh ? sets modes of operationCCacm or dcm ? settings to accommodate various panel sizes (panel time constant) ? averaging and noise settings ? measurement resolution ? auxiliary settings ? general part status reporting 2) fifo data readback command: 50h ? autonomous conversion mode (max11800/ max11801) ? allows reading fifo contents when operating in acm (max11800/max11801) 3) data readback commands: 52h to 5bh ? direct conversion mode (max11800/max11802) ? allows reading measurement results when in dcm 4) i 2 c readback registers: 52h to 58h ? direct conversion mode (max11801/max11803) ? allows reading measurement results when in dcm max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 45 start write address byte 1: device address stop w n3 n2 n1 n0 x conversion or measurement command n4 1 0 0 1 0 a1 a0 n5 n6 sda scl a a figure 30. i 2 c conversion and measurement commands
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 46 ______________________________________________________________________________________ byte bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 ack bit r6 r5 r4 r3 r2 r1 r0 x (dont care) 1/0 command or data 1/0 table 17. i 2 c command and data format: 8 bits plus ack 5) panel setup commands: 6ah to 6fh ? sets up panel prior to making x, y, z1, or z2 mea- surements 6) measurement commands: 70h to 7fh ? performs specified measurement (x, y, z1, and/or z2) the commands to read or write the user-accessible registers are always the same. however, the data for- mat varies based on whether using an spi or i 2 c inter- face. tables 16 and 17 show the differences between spi and i 2 c protocols. for spi, the r/w bit is embed- ded in the 8-bit byte and always occupies the lsb position. for i 2 c, the protocol is always 8-bit byte fol- lowed by an acknowledge bit, for a total of 9 bits. the lsb in i 2 c format is a dont care. in write mode, for i 2 c, the lsb is ignored internal to the max11800C max11803, so setting it to 0 or 1 has no effect. status and configuration registers the status and configuration registers are located in block 0x00 to 0x0b. see table 18. all user-configura- tion register write mode operations are pairable within the spi/i 2 c interface. multiple locations can be written under a single instruction with a register byte followed by a data. all user-configuration read-mode operations support autoincrement. for example, if location 0x00 is read back and more clock pulses are issued, readback will proceed through location 0x01 and so forth. the user should set all configuration registers to the desired values before issuing direct conversion operations or placing max11800/max11801 in autonomous mode. data readback commands autonomous conversion mode use the readback command 0x50 to read back available fifo data in autonomous conversion modes (auto = 1) (max11800/max11801). the oldest available data is read out first. data blocks vary from 32 to 64 bits in length, depending on the scan mode selected. reading back longer than one block results in reading back the next available block. the end-of-file indicator (event tag = 11) is read back when no unread data is available in the fifo. this command does not autoincrement and the register address does not advance beyond 0x50. see the fifo data block readback structure section for more details. direct conversion mode use the readback commands 0x52 to 0x5b to read back available measurement data gathered in direct conversion mode (auto = 0). random data access is supported within this register space and the commands autoincrement up to register 0x5b. the register address does not advance beyond register 0x5b. attempting to read back a pending conversion results in data being tagged invalid. see the direct conversion mode operations section for more details. the panel setup and conversion commands are not pairable in write mode as each command modifies the panel setting both during and after the command, based on conversion executions and cont bit set- tings. all direct conversion commands modify the expected i 2 c read register location to support the data streamlining protocol. table 21 shows the resulting read register settings by command type applicable to i 2 c variants. byte bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 r6 r5 r4 r3 r2 r1 r0 (cont) r/ w command or data 1/0 table 16. spi command and data format: 8 bits
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 47 hex* access auto- increment data length max11800/ max11801 max11802/ max11803 function autonomous conversion mode readback commands 50h r n inf yes no read next available fifo data block direct conversion mode readback commands 52h r y 8 yes yes x msb (direct conversion result) 53h r y 8 yes yes x lsb (direct conversion result) 54h r y 8 yes yes y msb (direct conversion result) 55h r y 8 yes yes y lsb (direct conversion result) 56h r y 8 yes yes z1 msb (direct conversion result) 57h r y 8 yes yes z1 lsb (direct conversion result) 58h r y 8 yes yes z2 msb (direct conversion result) 59h r y 8 yes yes z2 lsb (direct conversion result) 5ah r y 8 yes yes aux msb (direct conversion result) 5bh r n 8 yes yes aux lsb (direct conversion result) table 19. data readback command summary * both spi and i 2 c interfaces use a 7-bit register address format. i 2 c interfaces should left-justify the 7-bit addresses given in table 19 (e.g., to access register 50h, use the command byte construction {101_0000_x}, where x is a don't care). hex (note 1) access pairable auto- increment data length max11800/ max11801 max11802/ max11803 function 00h r no yes 8 yes yes (note 2) general status 01h r/w yes yes 8 yes yes general configuration 02h r/w yes yes 8 yes yes measurement resolution configuration 03h r/w yes yes 8 yes yes measurement averaging configuration 04h r/w yes yes 8 yes yes adc sample time configuration 05h r/w yes yes 8 yes yes panel setup times configuration 06h r/w yes yes 8 yes yes adc delay initial conversion configuration 07h r/w yes yes 8 yes yes touch-detect pullup times configuration 08h r/w yes yes 8 yes no autonomous mode timing configuration) 09h r/w yes yes 8 yes no aperture settings (auto) configuration 0ah r/w yes yes 8 yes yes auxiliary measurement configuration 0bh r/w yes yes 8 yes yes (note 2) operating mode configuration table 18. status and configuration registers note 1: both spi and i 2 c interfaces use a 7-bit register address format. i 2 c interfaces should left-justify the 7-bit addresses given in table 18 (e.g., to access register 0bh use the command byte construction {000_1011_x}, where x is a don't care). note 2: not all bits apply to the max11802/max11803. see the individual register definitions.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 48 ______________________________________________________________________________________ hex (note 1) r0 (cont) (note 2) access pairable command length max11800/ max11801 max11802/ max11803 function 60hC67h x yes yes reserved 69h (1) w n 8 yes yes x panel setup 6bh (1) w n 8 yes yes y panel setup 6dh (1) w n 8 yes yes z1 panel setup 6fh (1) w n 8 yes yes z2 panel setup 70h (0) w n 8 yes yes x, y combined command 72h (0) w n 8 yes yes x, y, z1 combined command 74h (0) w n 8 yes yes x, y, z1, z2 combined command 76h (0) w n 8 yes yes aux conversion 78h cont = 0 w n 8 yes yes x measurement 79h cont = 1 w n 8 yes yes x measurement 7ah cont = 0 w n 8 yes yes y measurement 7bh cont = 1 w n 8 yes yes y measurement 7ch cont = 0 w n 8 yes yes z1 measurement 7dh cont = 1 w n 8 yes yes z1 measurement 7eh cont = 0 w n 8 yes yes z2 measurement 7fh cont = 1 w n 8 yes yes z2 measurement table 20. conversion command summary panel setup and measurement commands tsc conversion commands are only to be used in direct conversion mode (auto = 0). conversion com- mands issued during autonomous mode are ignored. all panel setup and measurement operations are auto- mated when in autonomous mode (auto = 1). commands must be issued in write mode to be execut- ed. there are two types of commands: panel setup reg- isters (0x6x) and measurement/conversion registers (0x7x). all measurement commands indicate that the adc is used and the adc can begin to power up once the 0x7x header has been recognized. all measure- ment commands modify the target data register upon the conclusion of the measurement command. the cont bit impacts the setup of the panel and adc fol- lowing the command. for panel setup commands and combined commands, the user setting of this bit (r0) is ignored. for these commands, the internal assumption is shown in parentheses in table 22. the cont bit impacts the setup of the panel and/or adc following the command (see command descriptions for details). for some commands, the user setting of this bit (r0) is ignored; for these commands the internal assumption is shown in parentheses in tables 8 and 22. by definition, panel setup and measurement com- mands are not pairable in write mode as each com- mand modifies the panel setting both during the command and after it (based on conversion executions and cont bit settings). note 1: both spi and i 2 c interfaces use a 7-bit register address format. i 2 c interfaces should left-justify the 7-bit addresses given in table 20 (e.g., to access register 50h use the command byte construction {101_0000_x}, where x is a don't care). note 2: r0 bit is forced to 1 for panel setup commands, and forced to 0 for combined and aux commands. for measurement com- mands it is user selectable. cont = 0 means perform a measurement without continuation, while cont = 1 means perform a mea- surement with continuation. continuation mode maintains the present panel setup conditions after the conclusion of the measurement, and can be useful when performing multiple measurements of the same type.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 49 hex access pairable command length function 0x70h write no 8 x, y = combined command measurement 0x72h write no 8 x, y, z1 = combined command measurement 0x74h write no 8 x, y, z1, z2 = combined command measurement 0x76h write no 8 aux = conversion 0x78h write no 8 x = measurement, cont = 0 0x79h write no 8 x = measurement, cont = 1 0x7ah write no 8 y = measurement, cont = 0 0x7bh write no 8 y = measurement, cont = 1 0x7ch write no 8 z1 = measurement, cont = 0 0x7dh write no 8 z1 = measurement, cont = 1 0x7eh write no 8 z2 = measurement, cont = 0 0x7fh write no 8 z2 = measurement, cont = 1 table 21. measurement commands b i t 76543210 name adc_busy lpm tdm scan fifo_ovr fifo_int edge_int cont_int default 0 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7 adc_busy 0: adc is not in acq or conv state 1: adc is in acq or conv state this is for internal test only yes yes 6 lpm 0: device is not in lpm or standby mode 1: device is in lpm or standby mode yes yes 5 tdm 0: device is not in tdm mode 1: device is in tdm mode yes yes 4 scan 0: no scan or measurement in progress 1: scan or measurement in progress also indicates presence of a continuous touch in autonomous yes yes 3 fifo_ovr 0: fifo overflow has not occurred 1: fifo has overflowed since last readback operation enabled only if auto = 1 yes no 2 fifo_int 0: no unread data in fifo 1: new data available in fifo enabled only if auto = 1 yes no 1 edge_int 0: no touch event in progress 1: touch event in progress (cleared on etag = 10) enabled only if auto = 0 and edge_irq = 1 yes yes 0 cont_int 0: no touch present 1: touch present (or conversion in progress) enabled only if auto = 0 and edge_irq = 0 yes yes general status register (0x00) (read only) user configuration registers
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 50 ______________________________________________________________________________________ bit 7 6 5 4 3 2 1 0 name pwr_sav resx resy resz1 resz2 default 0 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 4 pwr_sav 0: internal adc runs at normal power 1: internal adc runs at reduced power and resolution this mode does limit the effective adc resolution: 12-bit conversions can be reduced to 10-bit accuracy 8-bit conversions should not be impacted yes yes 3:0 res_ resolution for x, y, z1, or z2 measurements 0: 12-bit conversion (see the pwr_sav description in this table) 1: 8-bit conversion yes yes measurement resolution configuration register (0x02) bit 7 6 5 4 3 2 1 0 name rt_sel hold_do pu_irq odn_irq mask_irq edge_irq edge_time[1:0] default 1 1 1 1 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7 rt_sel 0: 50k touch-detection pullup resistance 1: 100k touch-detection pullup resistance (panel settingnot to be confused with internal tirq pullup) yes yes 6 hold_do 0: dout internal bus holder disabled 1: dout internal bus holder enabled (applicable to spi version only) yes yes 5 pu_irq 0: disable irq internal pullup resistance 1: enable irq internal pullup resistance (open-drain mode only: odn_irq also high) yes yes 4 odn_irq 0: tirq is cmos buffered output 1: tirq is open-drain nmos output yes yes 3 mask_irq 0: enable tirq output 1: mask/disable tirq output (force high or high-z) yes yes 2 edge_irq 0: use continuous interrupt with direct conversion mode 1: use edge interrupt with direct conversion mode yes yes 1:0 edge_time[1:0] tirq low time for edge interrupt mode only 00: 4 x (2mhz oscillator clock period) = 2s 01: 16 x (2mhz oscillator clock period) = 8s 10: 64 x (2mhz oscillator clock period) = 32s 11: 128 x (2mhz oscillator clock period) = 128s yes yes general configuration register (0x01)
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 51 b i t 76543210 name t_sample_x[1:0] t_sample_y[1:0] t_sample_z1[1:0] t_sample_z2[1:0] default 0 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7:6 t_sample_x[1:0] yes yes 5:4 t_sample_y[1:0] yes yes 3:2 t_sample_z1[1:0] yes yes 1:0 t_sample_z2[1:0] sampling time for x, y, z1 or z2 measurements 00: 4 x (2mhz oscillator clock period) = 2s 01: 16 x (2mhz oscillator clock period) = 8s 10: 64 x (2mhz oscillator clock period) = 32s 11: 256 x (2mhz oscillator clock period) = 128s yes yes adc sampling time configuration register (0x04)* * time adc spends sampling panel before starting conversion process. this time plus the adc conversion time determines the sam- pling rate within averaging operations. be sure to allow adequate time to settle the adc capacitors given the panel effective s ource resistance. bit 7 6 5 4 3 2 1 0 name avg_x[1:0] avg_y[1:0] avg_z1[1:0] avg_z2[1:0] default 0 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7:6 avg_x[1:0] yes yes 5:4 avg_y[1:0] yes yes 3:2 avg_z1[1:0] yes yes 1:0 avg_z2[1:0] averaging sample depth for x, y, z1, or z2 measurements if avg_flt = 0 (see the operating mode configuration register (0x0b) section) 00: single sample, no averaging 01: take four samples, average two median samples 10: take eight samples, average four median samples 11: take 16 samples, average eight median samples if avg_flt = 1 (see the operating mode configuration register (0x0b) section) 00: single sample, no averaging 01: take four samples, average all samples 10: take eight samples, average all samples 11: take 16 samples, average all samples yes yes measurement averaging configuration register (0x03)* * the settings can be enabled and disabled through settings in the operating mode configuration register (0x0b), allowing for dyn amic configuration of averaging modes depending on operating mode.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 52 ______________________________________________________________________________________ note: these settings apply to measurement commands, combined commands, and autonomous conversion mode measurements and provide time for the panel to settle prior to beginning measurements. during these periods, the panel is set up, but the ad c remains powered down. users with low-impedance/fast settling panels should use setting 0000 (skip mode) if their panel can be s et- tled during the required 10s minimum delayed conversion time (see the delayed conversion configuration register (0x06) section). bit 7 6 5 4 3 2 1 0 name d_cv_xy[3:0] d_cv_z[3:0] default 0 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7:4 d_cv_xy[3:0] x, y panel plus adc setup times (position measurements) 0000: 10s 1000: 1ms 0001: 20s 1001: 2ms 0010: 50s 1010: 5ms 0011: 80s 1011: 10ms 0100: 100s 1100: 20ms 0101: 200s 1101: 50ms 0110: 500s 1110: 100ms 0111: 800s 1111: 200ms yes yes 3:0 d_cv_z[3:0] z panel plus adc setup times (pressure measurements) d_cv_z[3:0] has the same range as d_cv_xy[3:0] above. yes yes delayed conversion configuration register (0x06) note: these settings apply to measurement commands, combined commands, and autonomous conversion mode measurements and provide time for the panel and adc to settle prior to beginning measurements. during these periods, the panel is set up and the adc is powered up. in general, users with long panel settling requirements should minimize time in this mode, using increased panel setup times instead to save adc power. bit 7 6 5 4 3 2 1 0 name psuxy[3:0] psuz[3:0] default 0 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7:4 psuxy[3:0] x, y panel setup times (position measurements) 0000: 0s 1000: 1ms 0001: 20s 1001: 2ms 0010: 50s 1010: 5ms 0011: 80s 1011: 10ms 0100: 100s 1100: 20ms 0101: 200s 1101: 50ms 0110: 500s 1110: 100ms 0111: 800s 1111: 200ms yes yes 3:0 psuz[3:0] z panel setup times (pressure measurements) psuz[3:0] has the same range as psuxy[3:0] above. yes yes panel setup timing configuration register (0x05)
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 53 note: these settings apply to the end of all measurement and combined commands and are required for proper data tagging and interrupt management. the exception is direct conversion commands with cont = 1. these commands do not enter pur/puf inter- vals for the purpose of data tagging. * while 2s is the minimum pur interval listed, for this setting, the xpsw is not engaged, allowing for minimal power operation (essentially adding 2s to the puf time). bit 7 6 5 4 3 2 1 0 name pur[3:0] puf[3:0] default 0 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7:4 pur[3:0] rough pullup time (t pur ) 0000: 2s* 1000: 1ms 0001: 2s 1001: 2ms 0010: 4s 1010: 5ms 0011: 8s 1011: 10ms 0100: 10s 1100: 20ms 0101: 50s 1101: 50ms 0110: 100s 1110: 100ms 0111: 500s 1111: 200ms yes yes 3:0 puf[3:0] fine pullup time (t puf ) 0000: 10s 1000: 1ms 0001: 20s 1001: 2ms 0010: 50s 1010: 5ms 0011: 80s 1011: 10ms 0100: 100s 1100: 20ms 0101: 200s 1101: 50ms 0110: 500s 1110: 100ms 0111: 800s 1111: 200ms yes yes touch-detect pullup timing configuration register (0x07)
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 54 ______________________________________________________________________________________ bit 7 6 5 4 3 2 1 0 name aprx[3:0] apry[3:0] default 0 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7:4 aprx[3:0] x for aperture checking 0000 = 2 -1 lsb = aperture checking disabled 0001 = 2 (1-1) lsb = 1 lsb 0010 = 2 (2-1) lsb = 2 lsb 0011 = 2 (3-1) lsb = 4 lsb . . . 1001 = 2 (9-1) lsb = 256 lsb 1010 = 2 (10-1) lsb = 512 lsb 1011 = 2 (11-1) lsb = 1024 lsb 1100 = 2 (12-1) lsb = 2048 lsb 1101 = n/a = aperture checking disabled yes no 3:0 apry[3:0] y for aperture checking apry[3:0] has the same range as aprx[3:0] above. yes no aperture configuration register (0x09) note: these aperture settings apply in autonomous conversion mode only and control whether data meets the criteria for logging into the fifo. bit 7 6 5 4 3 2 1 0 name tinit[3:0] scanp[3:0] default 0 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7:4 tinit[3:0] initial period (time between touch and initial scan block, t init ) 0000: 10s 1000: 1ms 0001: 20s 1001: 2ms 0010: 50s 1010: 5ms 0011: 80s 1011: 10ms 0100: 100s 1100: 20ms 0101: 200s 1101: 50ms 0110: 500s 1110: 100ms 0111: 800s 1111: 200ms yes no 3:0 scanp[3:0] scan period (time between s uccessive scan blocks, t sp ) scanp[3:0] has the same range as tinit[3:0] above. yes no autonomous mode timing configuration register (0x08) note: these settings apply in autonomous conversion mode only.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 55 bit 7 6 5 4 3 2 1 0 name d_cv_a[3:0] t_sample_a[1:0] avga[1:0] resa default 0 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7:5 d_cv_a[3:0] delay initial auxiliary conversion 000: 10s 001: 100s 010: 500s 011: 1ms 100: 5ms 101: 10ms 110: 50ms 111: 100ms yes yes 4:3 t_sample_a[1:0] sampling time for auxiliary measurements 00: 4 x (2mhz oscillator clock period) = 2s 01: 16 x (2mhz oscillator clock period) = 8s 10: 64 x (2mhz oscillator clock period) = 32s 11: 256 x (2mhz oscillator clock period) = 128s yes yes 2:1 avga[1:0] averaging sample depth for auxiliary measurements if avg_flt = 0 (see the operating mode configuration register (0x0b) section) 00: single sample, no averaging 01: take four samples, average two median samples 10: take eight samples, average four median samples 11: take 16 samples, average eight median samples if avg_flt = 1 (see the operating mode configuration register (0x0b) section) 00: single sample, no averaging 01: take four samples, average all samples 10: take eight samples, average all samples 11: take 16 samples, average all samples yes yes 0 resa resolution for auxiliary measurements 0: 12-bit conversion (see the description of pwr_sav in the measurement resolution configuration register (0x02) section) 1: 8-bit conversion yes yes auxiliary measurement configuration register (0x0a) note: a delimiter refers to the auxiliary input (aux). auxiliary measurements can only be requested in direct conversion modes.
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 56 ______________________________________________________________________________________ b i t 76543210 name pwrdn amode[1:0] aper avg_flt en_avg_xy en_avg_z default 1 0 0 0 0 0 0 0 bit name description max11800/ max11801 max11802/ max11803 7 pwrdn 0: device is powered up and operational in either a direct or autonomous conversion mode (see amode[1:0] below). 1: device is powered down, otp is held in reset yes yes 6:5 amode[1:0] 00: direct conversion mode (auto = 0) 01: autonomous x and y scan (auto = 1) 10: autonomous x, y, z1 scan (auto = 1) 11: autonomous x, y, z1, z2 scan (auto = 1) yes no 4 aper 0: disregard aperture criteria 1: enable aperture criteria (spatial filter) (applies to autonomous modes only) yes no 3 avg_flt 0: use median averaging filters (ignore outliers) 1: use straight averaging filters yes yes 2 en_avg_xy 0: disable (x, y) position averaging in selected mode 1: enable (x, y) position averaging in selected mode yes yes 1 en_avg_z 0: disable (z1, z2) pressure averaging in selected mode 1: enable (z1, z2) pressure averaging in selected mode yes yes 0 reserved operating mode configuration register (0x0b)
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface ______________________________________________________________________________________ 57 touch screen x+ y+ x- y- gpio 0.1f dout clk din cs v dd v dd tirq din clk dout cs gnd aux aux input host processor max11800 max11802 touch screen x+ y+ x- y- gpio 1.5k 1.5k sda scl a0 a1 v dd v dd tirq sda scl a0 a1 gnd aux aux input host processor max11801 max11803 0.1f optional max11801/max11803 typical operating circuit max11800/max11802 typical operating circuit
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface 58 ______________________________________________________________________________________ package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . note that a ?? ?? or ??in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. chip information process: cmos aux x- cs y- dout v dd clk gnd 2 4 1 3 tirq x+ din a b c y+ max11800/max11802 + wlp top view aux x- a0 y- a1 v dd scl gnd 2 4 1 3 tirq x+ sda a b c y+ max11801/max11803 tqfn + + wlp 12 11 10 4 5 6 12 aux 3 987 y+ tirq y- x- max11801 max11803 a1 x+ v dd gnd a0 scl sda 12 11 10 4 5 6 12 aux 3 987 y+ tirq y- x- max11800 max11802 dout x+ v dd gnd cs clk din *ep tqfn + *ep *exposed pad. pin configurations package type package code outline no. land pattern no. 12 tqfn t1244+4 21-0139 90-0068 12 wlp w121a2+1 21-0009 refer to application note 1891
max11800?ax11803 low-power, ultra-small resistive touch-screen controllers with i 2 c/spi interface maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 59 ? 2010 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 0 7/09 initial release removed future status from the wlp packages in the ordering information table. 1 added a new note 1 about the wlp package to the absolute maximum ratings section. 8 1 11/09 corrected the pin names for the wlp packages in the pin description table and pin configurations . 14, 56 2 3/10 added soldering temperature (reflow) at +260 c. in the absolute maximum ratings section. 8 3 10/10 added information to differentiate the max11800/max11801 features and operating modes from the max11802/max11803 features and operating modes. all

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