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ST2226A version : a.010 issue date : 2004/04/12 file name : sp-ST2226A-a.010.doc total pages : 23 pwm-controlled constant current driver for led displays ?W@^?I? ?W@^?I? ?W@^?I? ?W@^?I? 9 9 9 9 ? ? ? ? 7 7 7 7 ? ? ? ? 1 1 1 1 silicon touch technology inc . 9-7f-1, prosperity road i, science based industrial pard, hsin-chu, taiwan 300, r.o.c tel 886-3-5645656 fax 886-3-5645626
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 1 ST2226A pwm-controlled constant current driver for led displays general description the ST2226A is a led driver incorporating shift registers, data latches, 16-channel constant current circuitry with current value set by an external resistor, 1024 gray level pwm (pulse width modulation) functional unit and time division capability. each channel can provide a maximum current of 60 ma. time division operation allows driving up to 1 or 2 leds with a single output channel (mode-1 and mode-2 respectively). block diagram figure 1. functional block diagram operation control pwm counter voltage reference driver (16-channel) comparator (16-channel) shift register and latch (10 bit 16-channel 2led) rext gcl k cmd[2:0] dclk din iout0 iout15 ?? dout
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 2 features ? constant current outputs with current value settings by an external resistor ? maximum output current: 60 ma ? time division output allows the driving of 1 or 2 leds with a single output ? maximum / minimum output voltage: 10v / 1.25v ? 10 bits luminance data with pwm current outputs ? serial shift-in architecture for luminance data in time division mode 1 and mode 2 absolute maximum ratings supply voltage (av dd , dv dd ) -0.3 to 6 v input voltage range (v in ) -0.3 to dv dd +0.3 v driver output voltage range (v out ) -0.3 to 10 v driver output current (i out ) 0 to 60 ma power dissipation (t a = 50 or less) 2.50, sdip28 1.32, sop28 2.92, qfn32 w thermal resistance ( ja ) 40.0, sdip28 75.9, sop28 34.2, qfn32 / w operating temperature range (t op ) -40 to 85 storage temperature range (t stg ) -55 to 150
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 3 pin connection (sdip28 / sop28 top view) pin assignment (sdip28 / sop28) pin no. name pin no. name 1 iout2 15 iout14 2 iout3 16 iout15 3 iout4 17 gnd 4 iout5 18 dout 5 iout6 19 gclk 6 iout7 20 dclk 7 ignd 21 rext 8 ignd 22 cmd[2] 9 iout8 23 cmd[1] 10 iout9 24 cmd[0] 11 iout10 25 din 12 iout11 26 vdd 13 iout12 27 iout0 14 iout13 28 iout1
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 4 pin connection (qfn32 bottom view) pin assignment (qfn32) pin no. name pin no. name pin no. name 1 din 12 ignd 23 gnd 2 vdd 13 ignd 24 dout 3 iout0 14 ignd 25 gclk 4 iout1 15 iout8 26 dclk 5 iout2 16 iout9 27 rext 6 iout3 17 iout10 28 ignd 7 iout4 18 iout11 29 ignd 8 iout5 19 iout12 30 cmd[2] 9 iout6 20 iout13 31 cmd[1] 10 iout7 21 iout14 32 cmd[0] 11 ignd 22 iout15 thermal pad ignd iout2 vdd iout0 cmd[0] din cmd[2] ignd rext dclk iout 11 gclk dout iout 1 5 iout 1 4 iout6 gnd iout3 iout4 iout5 ignd ignd ignd iout8 iout9 iout 1 0 iout 1 2 iout 1 3 iout 1 1 2 3 4 5 6 7 8 9 1 0 11 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 20 2 1 22 23 24 25 26 27 28 29 30 3 1 32 ignd ignd iout7 cmd[ 1 ] thermal pad
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 5 pin description name pin no. i/o description cmd[2:0] sdip/sop: 22, 23, 24 qfn: 30, 31, 32 i encoded commands for data transfer, time division operation and pwm display: cmd[2:0] command [000]: mode-1 time division operation / no operation for display [001]: mode-2 time division operation / no operation for display [010]: data transfer enable (shift-in) [011]: data latch strobe (capture) [100]: first led emitting [101]: second led emitting [110]: led emitting disable / iout disable (stop) [111]: test mode cmd commands are latched at the rising edges of dclk. there is one dclk latency between shift-in command latched and data shift-in. din sdip/sop: 25 qfn: 1 i serial input for luminance data (time division mode-1/2) dout sdip/sop: 18 qfn: 24 o serial output for luminance data (time division mode-1/2). dclk sdip/sop: 20 qfn: 26 i synchronous clock input for command and serial data transfer. the input data of din is synchronous to rising edges of dclk, and transferred to dout on falling edges of dclk. gclk sdip/sop: 19 qfn: 25 i clock input for pwm operation. iout0-15 sdip/sop: 27, 28, 1, 2 3, 4, 5, 6, 9, 10, 11, 12 13, 14, 15, 16 qfn: 3, 4, 5, 6, 9, 10, 15, 16, 17, 18, 19, 20, 21, 22 o led driver outputs.
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 6 rext sdip/sop: 21 qfn: 27 o driver current setting. led current is set to a current value by connecting an external resistor between rext and gnd. vdd sdip/sop: 26 qfn: 2 - power supply gnd sdip/sop: 17 qfn: 23 - analog and digital ground ignd sdip/sop: 7, 8 qfn: 11, 12, 13, 14, 28, 29, thermal pad - two ground-pin for driver outputs.
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 7 recommended operating conditions dc characteristics parameter min nom max unit supply voltage, dv dd , av dd 4.75 5 5.25 v driver output voltage when driver on, v out 1.25 - 5 v driver output voltage when driver off 1 , v out 0 - 10 v driver output current, i out 5 - 60 ma high-level input voltage, v ih 0.8dv dd - dv dd v low-level input voltage, v il 0 - 0.2 dv dd v high-level output current, i oh - - -1 ma low-level output current, i ol - - 1 ma operating free-air temperature 2 , t op -20 - 80 ac characteristics parameter test conditions min nom max unit dclk clock frequency, f dclk - - 15 mhz dclk pulse duration, t wh / t wl high or low level 20 - - ns dclk rise/fall time t r / t f - - 40 ns gclk clock frequency, f gclk - - 20 mhz gclk pulse duration, t wh / t wl high or low level 15 - - ns gclk rise/fall time t r /t f - - 20 ns setup time, t su cmd to dclk din to dclk dclk to cmd 25 25 25 - - ns hold time, t h / t wh cmd to dclk din to dclk dclk to cmd 25 25 25 - - ns 1. the driver output voltage including any overshoot stress has to be compliant with the maximum voltage (10v). 2. recommended junction temperature range is from ?20 to 150 .
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 8 electrical characteristics parameter test conditions min nom max unit high-level digital output voltage, v oh dv dd - 0.5 - - v low-level digital output voltage, v ol - - 0.5 v input current, i i - - 1 a supply current (digital) dclk = 10mhz, gclk = 10mhz 0.5 ma supply current (analog) rext = 2k 14 ma voltage reference, v bg rext = 2k ? 1.24 1.26 1.28 v driver output current, i out rext = 2k ? , v out = 2.0v 32.2 ma driver output leakage current, i ol - - 1 a driver current skew between channels, i ol1 v out = 2v, i = 40ma - 3 6 % driver current skew between chips, i ol2 v out = 2v, i = 40ma - 6 12 % switching characteristics, c l = 15pf, iout = 20ma parameter test conditions min nom max unit rise time, t r dout iout - - 5 25 10 40 ns fall time, t f dout iout - - 5 25 10 40 ns propagation delay, t d gclk to iout - 30 40 ns
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 9 typical control method 1) command sequence to manipulate ST2226A, we should properly control the cmd, din, dclk, and gclk as following steps: 1. issue command ? shift-in ?, and then enter luminance data din. note that ST2226A starts to shift-in data at the dclk rising edge next to the edge which latched shift-in command. 2. after data are completely entered, send command ? capture ? to save data in registers. 3. send command ? disable ?. this step is needed before the ?emitting? command to keep the chip synchronized. 4. issue command ? emitting? or ?disable ?. note that: a. ST2226A generates its output in one-shot fashion, i.e. the output after (1024) x t gclk is always zero. b. there are 2 gclk latencies between the latched led emitting/disable command and pwm start/stop. this is shown in figure 2. 5. repeat step 1~4. in the same frame, the luminance data doesn?t have to change, just repeat step 3~4. note that the second command ? emitting ? will be omitted if (1024) x t gclk pwm has not finished, unless the ? disable ? command is sent in advance. the process discussed above could be summarized in the following table and timing diagram. at the same time, dclk and gclk remain free running. table 1. example of command sequence frame n-1 frame n frame n+1 cmd nop 3 capture disable emitting / disable shift-in ? shift-in disable emitting / disable shift-in ? shift-in disable emitting / disable nop ? nop capture ? ? din ? ? ? don?t care. don?t care. don?t care. don?t care. shift-in data. ? shift-in data don?t care. don?t care. shift-in data ? shift-in data don?t care. don?t care. don?t care. don?t care. ? ? 3 we used the nops (no operation) to wait for the next frame data (at 60hz) ready.
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 10 2) led emitting time and current ST2226A adjusts the led luminance using pwm (pulse width modulation) technique. the luminance data (d v ) has a resolution of 10 bits (1024steps) and can be set independently for each led. the relationship between iout, luminance data, and emitting time is shown in figure 2. current iout time d v x t gclk ?led emitting? command issued 1024 x t gclk 2 x gclk figure 2. pwm current output 3) phase relationship of dclk and gclk matching ST2226A?s gclk and dclk is an important step in the system design. if there is a certain length of delay between the rising edge of dclk and of gclk, the command ? led emitting ?& ? led disable ? will not be correctly recognized, which will then cause the display data loss. it is safe to keep both of gclk and dclk rising at the same time, so that the frequencies of dclk and gclk have an integer multiple relationship. for the design which has a fixed, corresponding clock phase relationship between gclk & dclk, e.g. the display controller is built by fpgas, this clock phase problem is unlikely to happen. however, if it dose happen, try to control the clock phase, e.g. invert gclk, to solve this problem. on the contrary, for the design which can not control the clock phase, e.g. the display controller is built by microprocessors, the following sequential modification on ? emitting ? & ? disable ? commands is preferred to be employed in the design: 1. gate gclk. 2. issue ? emitting ? or ? disable ? command. 3. let go of gclk.
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 11 timing diagrams figure 3. timing diagram
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 12 application diagrams
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 13 detailed description 1) time division operation since ST2226A can drive 1 led or 2 leds, the user can choose either mode1 luminance data or mode2 luminance data. after the luminance data is given, a command should be issued so that the driver can operate in mode1 or in mode2. figure 4 shows the route of data shift-in in mode2. later we will explain the data structure of mode1 and mode2 in more details. figure 4. block diagram for primary bus. figure 5. shows how to switch between 2 leds. when ? led1 emitting ? command is sent, led1 pwm output will start 2 gclk later. at the same time, the switch of led1 should be turned on. on the other hand, led2 switch should be turned on when led2 pwm output starts. again, ? disable ? command must be sent before ? led1/led2 emitting ?. by periodically switching the emitting commands and led switches, we could drive 2 leds per channel. turn on one of the switches one of iout ST2226A system led1 emitting or led2 emitting figure 5. system configuration for mode 2 operation ch0 led1 ch0 led2 ch1 led1 ch1 led2 din dout ch15 led1 ch15 led2
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 14 2) serial shift-in luminance data in the mode1 operation, the data for shift registers and latches is set as {16(channel) x 10 bit (luminance) x 1(led)} whereas in mode2 operation, the data is set as {16(channel) x 10 bit (luminance) x 2(led)} configuration. the driver ic can remember both 2 sets of luminance data. the serial shift architecture assumes a fifo (first-in firs-out) discipline, hence in the mode1 operation, the most significant bit (msb, bit 9, channel 15) luminance data is the first data shifted in, whereas the least significant bit (lsb, bit 0, channel 0) is the last data bit in a data set. the data structure for the mode1 and mode2 is shown in the figure 6. and figure 7. respectively. d in channe l 0 1 2 ? 15 0 (lsb) 0 0 0 0 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 5 5 5 5 5 6 6 6 6 6 7 7 7 7 7 8 8 8 8 8 bit position for lumina -nce data 9 9 9 9 9 (msb ) d out figure 6. luminance data structure in mode 1
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 15 d in channe l 0 1 2 ? 15 0 (lsb) 0 0 0 0 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 5 5 5 5 5 6 6 6 6 6 7 7 7 7 7 8 8 8 8 8 led1 bit position for lumina -nce data 9 9 9 9 9 channe l 0 1 2 ? 15 0 0 0 0 0 1 1 1 1 1 2 2 2 2 2 3 3 3 3 3 4 4 4 4 4 5 5 5 5 5 6 6 6 6 6 7 7 7 7 7 8 8 8 8 8 led2 bit position for lumina -nce data 9 9 9 9 9 (msb ) d out figure 7. luminance data structure in mode 2
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 16 3) driver current output the drive current is set by an external resistor, rext, connected between the rext pin and gnd. varying the resistor value can adjust the current scale ranging from 5ma to the maximum 60 ma. note that the rext pin voltage is designed to be independent of supply voltage, temperature, and process variation, and is approximately 1.26v. the output current could be calculated roughly by the following equation: iout = (1.26 / rext) x 5 1 the full-scale current iout vs. rext is shown in figure 8. rext - iout 0 1 0 20 30 40 50 60 70 02468 1 0 1 2 1 4 rext (kohm) iout (ma/bit) figure 8. driver current as a function of r ext
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 17 4) power rating for the relationship between power dissipation and operating temperature, please refer to the following figure 9. 0 0.5 1 1 .5 2 2.5 3 3.5 4 050 1 00 1 50 200 ta (free-air tem perature) - c pd (total power dissipation) - w sdip sop qfn figure 9. power dissipation vs. operating temperature 5) advantages for application to understand what the advantages over on-off type drivers, we assume that in mode 1 operation, the frame rate is 60hz, dclk & gclk both run at 10mhz. we can shift in (1/60hz)/(1/10mhz)=167k bits per frame. one channel takes 10 bits, thus 167k/10=16.7k channels (single color pixels). for two dimension display, we take the square root of 16.7k pixels, which equals 129. the resolution, in this case is 129*129. we can round the data a little bit, and we can construct a 128*128 image by connecting 1024 driver ics. (1,024 ea drivers*16 channels 16,384 bit). P
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 18 within a frame, there are 1024*16*10=163k dclk & gclk cycles, and we know that the pwm takes 1024 gclk cycles and is one-shot. so we can issue up to 163k/1024=160 pwm cycles within a frame. this can be used as an 160-level total brightness control in addition to the 1024-level pixel-dependent luminance control. these 160- ?led1 emitting? shall be issued periodically within a frame. each time when issuing the ?led1 emitting? command, the shift-in process will be pended for a few cycles; however, we can resume feeding the data right after the ?led1 emitting? command is issued. to make the total brightness at full scale, all 160 ?led1 emitting? commands should be issued. to make the total brightness half of the full scale, we can issue 80-?led1 emitting? commands in companion with 80-?led disable? commands, so that all the 128*128 leds are half of their brightness. a comparison table for pwm led driver vs. on-off type is provided for reference. table 2. comparison between pwm and on-off free running pwm on-off frame rate 60 60 no. shift-in pixels 128 x 128 128 x 128 grayscale for each pixel 1024 1024 grayscale for overall panel 160 1 clocks needed per frame 167k 16.8meg clock rate 10 mhz 1.0 ghz 4 4 surely out of spec. can?t realize in this configuration. system designs for on-off type drivers thus need to reduce frame rate or the no. shift-in pixels or grayscale level for each pixel.
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 19 package outline dimension sdip28 e e b d e 1 0.060typ. l 0. 1 00typ. a a 1 0.0 1 8typ. a2 seating plane e b l e e 1 d a2 a 1 a symbols min. nom. max. dimension in inch - - 0.2 1 0 0.0 1 5 - - 0. 1 25 0. 1 30 0. 1 35 1 .385 1 .390 1 .400 0.283 0.288 0.293 0.3 1 bsc 0. 11 5 0. 1 30 0. 1 50 0.330 0.350 0.370 0 7 1 5 note: 1 . jedec outline : n/a
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 20 sop28
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 21 qfn32 dimension (mm) dimension (mil) symbol min. nom. max. min. nom. max. a 0.70 0.75 0.80 27.6 29.5 31.5 a1 0 0.02 0.05 0 0.79 1.97 a3 0.25 ref 9.84 ref b 0.18 0.23 0.30 7.09 9.06 11.81 d 5.00 bsc 196.85 bsc d2 1.25 2.70 3.25 49.21 106.30 127.95 e 5.00 bsc 196.85 bsc e2 1.25 2.70 3.25 49.21 106.30 127.95 e 0.50 bsc 19.69 bsc l 0.30 0.40 0.50 11.81 15.75 19.69 y 0.10 3.94 note: 1.dimensioning and tolerancing conform to asme y145.5m-1994. 2. refer to jedec std. mo-220 whhd-2 issue a 1 6 1 6 1 6 1 69 9 9 9 1 7 1 7 1 7 1 7 24 24 24 24 25 25 25 25 32 32 32 32 1 1 1 1 8 8 8 8 bottom view d2 d e b e l e e2 seating plane a3 a 1 a y y y y c c c c 0. 1 0 0. 1 0 0. 1 0 0. 1 0 c c c c 0. 1 0 0. 1 0 0. 1 0 0. 1 0 m c c c ca a a ab b b b top view 9 9 9 9 1 6 1 6 1 6 1 6 8 8 8 8 1 7 1 7 1 7 1 7 24 24 24 24 1 1 1 1 32 32 32 32 25 25 25 25 0.25 0.25 0.25 0.25 c c c c 0.25 0.25 0.25 0.25 c c c c
c???? c???? c???? c???? silicon touch technology inc. ST2226A ST2226A version a.010 page 22 the products listed herein are designed for ordinary electronic applications, such as electrical appliances, audio-visual equipment, communications devices and so on. hence, it is advisable that the devices should not be used in medical instruments, surgical implants, aerospace machinery, nuclear power control systems, disaster/crime-prevention equipment and the like. misusing those products may directly or indirectly endanger human life, or cause injury and property loss. silicon touch technology, inc. will not take any responsibilities regarding the misusage of the products mentioned above. anyone who purchases any products described herein with the above-mentioned intention or with such misused applications should accept full responsibility and indemnify. silicon touch technology, inc. and its distributors and all their officers and employees shall defend jointly and severally against any and all claims and litigation and all damages, cost and expenses associated with such intention and manipulation.

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