View MAX1299_1816491.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

general description the max1298/MAX1299 implement local and remote temperature sensing with 12-bit resolution, using +5v and +3v supply voltages, respectively. accuracy is ?? from 0 to +70?, with no calibration needed. the devices feature an algorithmic switched-capacitor ana- log-to-digital converter (adc), an on-chip clock, and a 3-wire serial interface compatible with spi, qspi, and microwire. the max1298/MAX1299 also perform fully differential voltage measurements with 12-bit resolution and sepa- rate track-and-hold (t/h) for positive and negative inputs. both devices accept versatile input modes con- sisting of two 3-channel signal pairs, five 1-channel sig- nals relative to a floating common, or v dd /4 relative to ground. an external reference may be used for more accurate voltage measurements. typical power consumption is only 1.3mw (MAX1299). a shutdown mode and two standby modes provide multiple strategies for prolonging battery life in portable applications that require limited sampling throughput. the max1298/MAX1299 are available in 16-pin ssop packages. ________________________applications temperature/voltage supervision of workstations and communications equipment hand-held instruments medical equipment industrial process control features local and remote temperature sensing 12-bit resolution for temperature and voltage inputs ?? accuracy from -40? to +85? fully differential inputs single-supply operation +4.75v to +5.25v (max1298) +2.7v to +3.6v (MAX1299) 3-wire spi/qspi/microwire-compatible interface internal precision voltage reference 2.50v (max1298) 1.20v (MAX1299) space-saving 16-pin ssop package max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc ________________________________________________________________ maxim integrated products 1 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 ain1 ain0 ain5 ref gnd v dd sclk din dout top view max1298 MAX1299 ssop sho ain2 gnd ain3 ain4 sstrb cs pin configuration 19-1726; rev 0; 5/00 for free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800. for small orders, phone 1-800-835-8769. ordering information *future product?ontact factory for availability. typical operating circuit appears at end of data sheet. spi and qspi are trademarks of motorola, inc. microwire is a trademark of national semiconductor corp. part temp. range pin- package temp. sense accuracy ( c) max1298 aeae -40 c to +85 c 16 ssop 0.75 max1298beae* -40 c to +85 c 16 ssop 1.0 max1298ceae -40 c to +85 c 16 ssop 4.0 MAX1299 aeae -40 c to +85 c 16 ssop 0.75 MAX1299beae* -40 c to +85 c 16 ssop 1.0 MAX1299ceae -40 c to +85 c 16 ssop 4.0
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v dd = 4.75v to 5.25v (max1298), v dd = +2.7v to 3.6v (MAX1299), external reference, v ref = +2.5v (max1298), v ref = +1.2v (MAX1299), f sclk = 2.5mhz, t a = t min to t max , unless otherwise noted. typical values are at t a = +25 c.) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v dd to gnd. -0.3v to +6v sho to gnd ...............................................-0.3v to (v dd + 0.3v) analog inputs to gnd (ain0, ain1, ain2, ain3, ain4, ain5, ref).............................................-0.3v to (v dd + 0.3v) digital inputs to gnd (din, sclk, cs )......-0.3v to (v dd + 0.3v) digital outputs to gnd (dout, sstrb) ....-0.3v to (v dd + 0.3v) digital output sink current .. 25ma maximum current into any pin .50ma continuous power dissipation (t a = +70 c) 16-pin ssop (derate 8.00mw/ c above +70 c) ........667mw operating temperature range max129_ _eae ...............................................-40 c to +85 c junction temperature.... +150 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10s) .... +300 c parameter symbol conditions min typ max units dc accuracy (note 1) resolution res 12 bits relative accuracy (note 2) inl 1 lsb differential nonlinearity dnl 1 lsb offset error inputs ain0 ? ain5 2 lsb offset temperature coefficient 10 v/ c gain error inputs ain0 ? ain5, offset nulled 4 lsb v dd /4 absolute error 2 lsb gain temperature coefficient 2 ppm/ c channel-to-channel offset matching 0.5 lsb conversion rate voltage measurement 1.1 conversion time (note 3) t conv temperature measurement 2.2 ms track/hold acquisition time t acq 16 s aperture delay t apr 30 ns internal clock frequency f clk 57.6 62.3 65.5 khz analog inputs (ain0 ? ain5) input voltage range (note 4) measurement with respect to in-, figure 1 -2v ref +2v ref v common-mode range 0 v dd v input current (note 5) 0.1 5 a input capacitance 16 pf
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc _______________________________________________________________________________________ 3 electrical characteristics (continued) (v dd = 4.75v to 5.25v (max1298), v dd = +2.7v to 3.6v (MAX1299), external reference, v ref = +2.5v (max1298), v ref = +1.2v (MAX1299), f sclk = 2.5mhz, t a = t min to t max , unless otherwise noted. typical values are at t a = +25 c.) parameter symbol conditions min typ max units digital inputs input voltage low v il 0.8 v input voltage high v ih v d d - 0.8 v input hysteresis v hyst 0.2 v input leakage current i in 1 a input capacitance 16 pf digital outputs v output low voltage v ol i sink = 5ma 0.6 v output high voltage v oh i source = 0.5ma v d d - 0.6 v three-state output leakage current i out 10 a three-state output capacitance 15 pf power requirements max1298 4.75 5.25 positive supply voltage v dd MAX1299 2.7 3.6 v max1298 390 ful l - on, vol tag e m easur em ents, i nter nal r efer ence MAX1299 350 max1298 310 ful l - on, vol tag e m easur em ents, exter nal r efer ence MAX1299 280 max1298 440 500 full-on, temperature measure- ments, internal reference MAX1299 400 500 max1298 360 full-on, temperature measure- ments, exter nal r efer ence MAX1299 330 standby, sclk = gnd 120 standby-plus, sclk = gnd 190 positive supply current (note 6) i dd shutdown, sclk = gnd 2 10 a power-supply rejection ratio psrr (note 7) 50 65 db internal voltage reference characteristics v dd = 5v max1298 2.494 2.50 2.506 reference voltage v ref v dd = 3v MAX1299 1.197 1.20 1.203 v reference tempco tc v ref 20 ppm/ c output short-circuit current 1.25 ma capacitive bypass at ref 0.1 f max1298 130 ref output noise f n = 10hz to 10khz MAX1299 65 v rms max1298 +3.0 ref line regulation MAX1299 +0.2 mv/v max1298 4 10 ref load regulation 0 to 100 a output current (note 8) MAX1299 2 10 v/ a
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc 4 _______________________________________________________________________________________ parameter symbol conditions min typ max units external voltage reference characteristics max1298 0.8 2.5 reference voltage range v ref MAX1299 0.8 1.2 v converting 10 ref input resistance shutdown 25 m ? ref input capacitance 24 pf internal temperature measurement characteristics resolution 0.13 c max129_a 0.75 max129_b 1 t a = +85 c, p d = 1mw max129_c 1 max129_a 0.75 max129_b 1 t a = 0 c to +70 c max129_c 2 max129_a 0.75 max129_b 1 output error (notes 1, 9) t a = -40 c to 0 c, t a = +70 c to +85 c max129_c 4 c power-supply rejection ratio psrr (note 7) 0.2 c/v noise 0.18 c rms external temperature measurement characteristics output error 2n3904 (note 10) 2 4 c remote diode excitation (1x) 10 a remote diode excitation (10x) 100 a electrical characteristics (continued) (v dd = 4.75v to 5.25v (max1298), v dd = +2.7v to 3.6v (MAX1299), external reference, v ref = +2.5v (max1298), v ref = +1.2v (MAX1299), f sclk = 2.5mhz, t a = t min to t max , unless otherwise noted. typical values are at t a = +25 c.)
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc _______________________________________________________________________________________ 5 timing characteristics (v dd = +4.75v to 5.25v (max1298), v dd = +2.7v to +3.6v (MAX1299), external reference, v ref = +2.5v (max1298), v ref = +1.2v (MAX1299), f sclk = 2.5mhz, t a = t min to t max , unless otherwise noted. typical values are at t a = +25 c.) (figures 4, 6) parameter symbol conditions min typ max units sclk frequency f sclk 2.5 mhz sclk pulse width low t cl 200 ns sclk pulse width high t ch 200 ns cs low to sclk high t css 100 ns sclk high to cs setup t csh 100 ns cs pulse width t cs 100 ns sclk high to cs low setup t cs0 50 ns sclk high to cs high setup t cs1 100 ns din setup to sclk high time t ds 100 ns din hold time t dh 0ns sclk fall to output data valid t do r l = 100k ? , c l = 50pf 150 ns cs fall to output enable t dv r l = 100k ? , c l = 50pf 150 ns cs rise to output disable t tr r l = 100k ? , c l = 50pf 50 ns sstrb rise to sclk rise t sclk 0ns sclk fall to sstrb fall t sstrb 200 ns note 1: tested at v dd = +5.0v (max1298) and v dd = +3.0v (MAX1299). note 2: relative accuracy is the deviation of the analog value at any code from its theoretical value after the full-scale range has been calibrated. note 3: conversion time is defined as the number of clock cycles (64 for voltage measurements, 125 for temperature measure- ments) multiplied by the internal clock period. note 4: individual analog input voltages cannot extend beyond the power-supply rails. note 5: input resistance is typically 250m ? ; 5a limit reflects limitations in production testing. note 6: specifications for full-on status assume continuous conversions. power modes are software selected (table 4). note 7: measured at v fs(+4.75v) - v fs(+5.25v) for the max1298 and at v fs(+2.7v) - v fs(+3.6v) for the MAX1299. note 8: external load should not change during conversions for specified accuracy. note 9: excludes noise and self-heating effects. output error for max129_c guaranteed by design. note 10: external temperature sensing over -40 c to +85 c range, device at +25 c. guaranteed by design.
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc 6 _______________________________________________________________________________________ typical operating characteristics (t a = +25 c, unless otherwise noted.) -1.0 -0.4 -0.6 -0.8 -0.2 0 0.2 0.4 0.6 0.8 1.0 -2500 -1250 0 1250 2500 max1298 integral nonlinearity vs. output code max1298/9-01 output code integral nonlinearity (lsb) -1.0 -0.4 -0.6 -0.8 -0.2 0 0.2 0.4 0.6 0.8 1.0 -2500 -1250 0 1250 2500 MAX1299 integral nonlinearity vs. output code max1298/9-02 output code integral nonlinearity (lsb) -1.0 -0.4 -0.6 -0.8 -0.2 0 0.2 0.4 0.6 0.8 1.0 -2500 -1250 0 1250 2500 max1298 differential nonlinearity vs. output code max1298/9-03 output code differential nonlinearity (lsb) -1.0 -0.4 -0.6 -0.8 -0.2 0 0.2 0.4 0.6 0.8 1.0 -2500 -1250 0 1250 2500 MAX1299 differential nonlinearity vs. output code max1298/9-04 output code differential nonlinearity (lsb) 0 150 100 50 200 250 300 350 400 450 500 4.7 4.9 4.8 5.0 5.1 5.2 max1298 supply current vs. supply voltage (voltage measurement mode) max1298/9-05 supply voltage (v) supply current ( a) external reference internal reference 0 150 100 50 200 250 300 350 400 450 500 2.7 3.1 2.9 3.3 3.5 MAX1299 supply current vs. supply voltage (voltage measurement mode) max1298/9-06 supply voltage (v) supply current (?) external reference internal reference 0 150 100 50 200 250 300 350 400 450 500 4.7 4.9 4.8 5.0 5.1 5.2 max1298 supply current vs. supply voltage (temperature measurement mode) max1298/9-07 supply voltage (v) supply current ( a) external reference internal reference 0 150 100 50 200 250 300 350 400 450 500 2.7 3.1 2.9 3.3 3.5 MAX1299 supply current vs. supply voltage (temperature measurement mode) max1298/9-08 supply voltage (v) supply current (?) external reference internal reference 0 150 100 50 250 200 450 400 350 300 500 -40 -20 0 20 40 60 80 max1298 supply current vs. temperature (voltage measurement mode) max1298/9-09 temperature (?) supply current (?) external reference internal reference
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc _______________________________________________________________________________________ 7 typical operating characteristics (continued) (t a = +25 c, unless otherwise noted.) 0 150 100 50 250 200 450 400 350 300 500 -40 -20 0 20 40 60 80 MAX1299 supply current vs. temperature (voltage measurement mode) max1298/9-10 temperature ( c) supply current (a) external reference internal reference 0 150 100 50 250 200 450 400 350 300 500 -40 -20 0 20 40 60 80 max1298 supply current vs. temperature (temperature measurement mode) max1298/9-11 temperature ( c) supply current (a) external reference internal reference 0 150 100 50 250 200 450 400 350 300 500 -40 -20 0 20 40 60 80 MAX1299 supply current vs. temperature (temperature measurement mode) max1298/9-12 temperature ( c) supply current (a) external reference internal reference 0 150 100 50 200 250 300 350 400 450 500 4.7 4.9 4.8 5.0 5.1 5.2 max1298 power-down supply current vs. supply voltage max1298/9-13 supply voltage (v) supply current ( a) standby standby+ MAX1299 power-down supply current vs. supply voltage 0 150 100 50 200 250 300 350 400 450 500 2.7 3.1 2.9 3.3 3.5 max1298/9-14 supply voltage (v) supply current (a) standby standby+ 0 150 100 50 250 200 450 400 350 300 500 -40 -20 0 20 40 60 80 max1298 power-down supply current vs. temperature max1298/9-15 temperature ( c) supply current (a) standby standby+ 0 150 100 50 250 200 450 400 350 300 500 -40 -20 0 20 40 60 80 MAX1299 power-down supply current vs. temperature max1298/9-16 temperature ( c) supply current (a) standby standby+ 2.52 2.51 2.50 2.49 2.48 4.7 5.0 4.8 4.9 5.1 5.2 max1298 internal reference voltage vs. supply voltage max1298/9-17 supply voltage (v) reference voltage (v) 1.22 1.21 1.20 1.19 1.18 2.7 3.1 2.9 3.3 3.5 MAX1299 internal reference voltage vs. supply voltage max1298/9-18 supply voltage (v) reference voltage (v)
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc 8 _______________________________________________________________________________________ typical operating characteristics (continued) (t a = +25 c, unless otherwise noted.) 2.48 2.49 2.50 2.51 2.52 max1298 internal reference voltage vs. temperature max1298/9-19 temperature ( c) reference voltage (v) -40 20 40 -20 0 60 80 1.18 1.19 1.20 1.21 1.22 MAX1299 internal reference voltage vs. temperature max1298/9-20 temperature ( c) reference voltage (v) -40 20 40 -20 0 60 80 1.0 0.5 0 -0.5 -1.0 4.7 5.0 4.8 4.9 5.1 5.2 max1298 offset vs. supply voltage max1298/9-21 supply voltage (v) offset (lsb) 1.0 0.5 0 -0.5 -1.0 2.7 3.1 2.9 3.3 3.5 MAX1299 offset vs. supply voltage max1298/9-22 supply voltage (v) offset (lsb) -1.0 -0.5 0 0.5 1.0 max1298 offset vs. temperature max1298/9-23 temperature ( c) offset (lsb) -40 20 40 -20 0 60 80 -1.0 -0.5 0 0.5 1.0 MAX1299 offset vs. temperature max1298/9-24 temperature ( c) offset (lsb) -40 20 40 -20 0 60 80
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc _______________________________________________________________________________________ 9 typical operating characteristics (continued) (t a = +25 c, unless otherwise noted.) -1.0 -0.5 0 0.5 1.0 max1298 gain error vs. temperature max1298/9-27 temperature ( c) gain error (lsb) -40 20 40 -20 0 60 80 -1.0 -0.5 0 0.5 1.0 MAX1299 gain error vs. temperature max1298/9-28 temperature ( c) gain error (lsb) -40 20 40 -20 0 60 80 -1.0 -0.5 0 0.5 1.0 -60 -20 20 60 -40 0 40 80 100 max1298 temperature error vs. internal diode temperature max1298/9-29 temperature ( c) temperature error ( c) -1.0 -0.5 0 0.5 1.0 -60 -20 20 60 -40 0 40 80 100 MAX1299 temperature error vs. internal diode temperature max1298/9-30 temperature ( c) temperature error ( c) -2.0 -1.0 -1.5 0 -0.5 0.5 1.0 1.5 2.0 -60 -20 0 -40 20 40 60 80 100 max1298 temperature error vs. remote diode temperature max1298/9-31 temperature ( c) temperature error ( c) -2.0 -1.0 -1.5 0 -0.5 0.5 1.0 1.5 2.0 -60 -20 0 -40 20 40 60 80 100 MAX1299 temperature error vs. remote diode temperature max1298/9-32 temperature ( c) temperature error ( c)
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc 10 ______________________________________________________________________________________ pin description pin name function 1 ain1 analog input 1. negative differential input relative to ain0 or positive differential input relative to ain5 (table 5). connect to the cathode of external diode 1 for remote temperature sensing. 2 sho shield output. used to suppress leakage currents at the anodes of remote temperature sensors (see remote diode shielding ). may also be connected to the shield of twisted-pair input cables used for remote temperature measurements. leave unconnected for other applications. 3 ain2 analog input 2. positive differential input relative to ain3 or positive differential input relative to ain5 (table 5). connect to the anode of external diode 2 for remote temperature sensing. 4 ain3 analog input 3. negative differential input relative to ain2 or positive differential input relative to ain5 (table 5). connect to the cathode of external diode 2 for remote temperature sensing. 5 ain4 analog input 4. positive differential input relative to ain5 (table 5). 6 gnd ground. connect to pin 13. 7 sstrb serial strobe output. sstrb goes low at the beginning of an a/d conversion, and it goes high when the conversion is finished. 8 cs active-low chip select. data will not be clocked into din unless cs is low. when cs is high, dout is at high impedance. 9 dout serial data output. dout transitions on the falling edge of sclk. 10 din serial data input. din latches data on the rising edge of sclk. 11 sclk serial clock input. clocks data in and out of the serial interface. 12 v dd positive supply voltage. bypass with a 0.1 f capacitor to gnd (pin 13). 13 gnd ground (star ground) 14 ref reference-buffer output/adc reference input. reference voltage for a/d conversion. bypass to gnd (pin 13) with a 0.1 f capacitor. select reference mode by writing to configuration byte (table 2). 15 ain5 analog input 5. negative differential input relative to ain0 ain4 (table 5). 16 ain0 analog input 0. positive differential input relative to ain1 or positive differential input relative to ain5 (table 5). connect to the anode of external diode 1 for remote temperature sensing.
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc ______________________________________________________________________________________________________ 11 detailed description the max1298/MAX1299 are low-power, serial-output, multichannel adcs with temperature-sensing capability for thermostatic, process-control, and monitoring appli- cations. an algorithmic switched-capacitor converter with t/h circuitry for both positive and negative inputs supports fully differential 12-bit conversions from an internal temperature sensor, two external temperature sensors, or voltage sources in a variety of channel con- figurations. microprocessor (p) control is made easy through a flexible 3-wire serial interface. figure 1 shows a simplified functional diagram of the internal architecture for the max1298/MAX1299. in tem- perature-sensing mode, the multiplexer (mux) steers bias currents through internal or external diodes while the adc computes their temperature in relation to changes in forward voltage. channels not used for tem- perature measurement can be configured to measure other system voltages. input register diode bias control control logic input mux output register clock 12-bit adc shield output t/h t/h in + in - v dd gnd dout cs sclk din ain0 ain1 ain2 ain3 ain4 ain5 v dd /4 sho ref ref max1298 MAX1299 figure 1. functional diagram
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc 12 ______________________________________________________________________________________ converter operation figure 2 shows a simplified model of the converter input structure. once initiated, a voltage conversion requires 64 f clk periods, where f clk is the internal master clock. each conversion is preceded by 13 f clk periods of warm-up time, performed in twelve 4 f clk period cycles, and followed by 3 f clk periods to load the output register. sstrb falls at the beginning of a conversion and rises at the end of a conversion. inputs in+ and in- charge capacitors c holdp and c holdn , respectively, during the acquisition interval that occurs during the first f clk period of the first con- version cycle. in the second f clk period, the t/h switches open so that charge is retained on c holdp and c holdn as a sample of the differential voltage between in+ and in-. this charge is transferred to the adc during the third and fourth f clk periods. the reference sampling process begins in the second conversion cycle and continues until the conversion is complete. sampling occurs during the second and fourth f clk periods to yield an effective doubling of the reference voltage. the reference sampling requirement is signal dependent and may or may not occur in every subsequent conversion cycle. temperature conversion is essentially nothing more than subtracting the results of two sequential voltage conver- sions. the only difference is that output registers are not loaded at the end of the first conversion. thus, tempera- ture conversions require 2 x 64 - 3 = 125 f clk periods. figures 3a and 3b show timing diagrams for voltage and temperature conversions, respectively. track/hold the t/h stage for the max1298/MAX1299 is a simple switched-capacitor sampling operation. the time required for the t/h stage to acquire an input signal is a function of how fast its input capacitance is charged. if the signal source impedance is high, the acquisition time lengthens and more time must be allowed between conversions. the acquisition time (t acq ) is the maximum time the device takes to acquire the signal. calculate this with the following equation: t acq = 7 (r s + r in ) c in where r s is the source impedance of the input signal, r in is the t/h input impedance (40k ? ), and c in is the timing/control logic fully differential a/d output gain of 2 in+ in- ref track and hold c holdp 4pf c holdn 4pf c ref 4pf r r 30k r in 40k r in 40k t/h t/h figure 2. converter input structure
13 f clks warmup 44 f clks convertion cycles 2 12 reference sampling 3 f clks subtraction and write to output register 48 f clks convertion cycles 1 12 13 f clks warmup input acquisition input acquisition sstrb fclk 4 f clks conversion cycle 1 first conversion second conversion max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc ______________________________________________________________________________________ 13 input sampling capacitance of the adc (4pf). source impedances below 100k ? have no significant effect on max1298/MAX1299 ac performance. analog input protection internal protection diodes clamp the analog inputs to v dd and gnd, so channels can swing within gnd - 0.3v and v dd + 0.3v without damage. however, for accurate conversions, the inputs should not extend beyond the supply rails. if an off-channel analog input extends beyond the supply rails, limit the input current to 2ma. serial digital interface the max1298/MAX1299 feature a serial interface that is fully compatible with spi, qspi, and microwire devices. for spi/qspi, ensure that the cpu serial inter- face runs in master mode so it generates the serial clock signal. select a 2.5mhz clock frequency or less, and set zero values for clock polarity (cpol) and phase (cpha) in the p control registers. figure 4 shows detailed serial interface timing information. see tables 2 5 for programming information. 13 f clks warmup 3 f clks write to output register input acquisition f clks sstrb fclk ref acquisition 1 ref acquisition 2 44 f clks conversion cycle 1 conversion cycles 2 12 reference sampling figure 3b. temperature conversion timing diagram figure 3a. voltage conversion timing diagram
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc 14 ______________________________________________________________________________________ input data format input data (configuration and conversion bytes) are clocked into the max1298/MAX1299 at din on the ris- ing edge of sclk when cs is low. the start bit (msb) of an input data byte is the first logic 1 bit that arrives: after cs falls, or after receipt of a complete configuration byte with no conversion in progress, or after 16 bits have been clocked onto dout following a conversion. output data format output data from the max1298/MAX1299 are clocked onto dout on the falling edge of sclk in the form of two 8-bit words, msb first (table 1). for temperature conver- sions, the output is 12-bit binary (d10 s0) padded with 2 leading extraneous bits and two trailing zeros. for volt- age conversions, the output is 12-bit two s-complement binary (d11 d0) with 1 sub-bit and two trailing zeros. figure 5 shows the bipolar transfer function. performing a conversion on power-up, the max1298/MAX1299 defaults to shut- down mode. start a conversion by transferring a configu- ration byte and a conversion byte into din with the control formats shown in tables 2 and 3, respectively. (see power modes for related discussion.) sstrb goes low on the falling edge of the last bit of the conversion byte, and it returns high when the conversion is complete. for best noise performance, sclk should remain low while sstrb is low. typical conversion times are 2.2ms for temperature measurements and 1.1ms for voltage measurements. the msb of the 2 output bytes is present at dout starting at the rising edge of sstrb. successive sclk falling edges shift the two 8-bit data bytes out from an internal register. additional (>16) sclk edges will result in zeros on dout. sstrb does not go into a high-impedance state when cs goes high. pulling cs high prevents data from being clocked in or out, but it does not adversely affect a conversion in progress. figure 6 shows sstrb timing details. subsequent conversions with the same reference mode do not require a configuration byte. t css t ds t ch t cs1 t cso t csh t cs t cl t dv dout din sclk cs t dh t do t tr valid valid valid x x x figure 4. detailed serial interface timing 011111111111 011111111110 000000000010 000000000001 000000000000 111111111111 111111111110 111111111101 100000000010 100000000001 output code + fs = + 2v ref - fs = - 2v ref 1lsb = 2v ref 2048 0 + fs - 1lsb - fs + 1lsb in + - in - (lsb) figure 5. bipolar transfer function
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc ______________________________________________________________________________________ 15 reference selection select between internal and external voltage modes through bit ref of the configuration byte. set ref = 1 for internal reference mode and ref = 0 for external reference mode. internal reference the max1298 has a 2.50v internal reference, while the MAX1299 has a 1.20v internal reference. both are fac- tory trimmed for accuracy. when internal reference is selected, ref can be used to drive an external load with 100a capability. bypass ref to gnd with a 0.1f (min) capacitance. wake-up time is c x 2.5 x 10 4 s for the max1298 and c x 1.2 x 10 4 s for the MAX1299. external reference the max1298 can directly accept reference voltages at ref from 0.8v to 2.5v, while the MAX1299 can directly accept reference voltages from 0.8v to 1.2v. bypass ref to gnd with a 0.1f capacitor. temperature mea- surements always use internal reference. power modes the max1298 (MAX1299) typically requires supply cur- rents of 380a (350a) or 310a (280a) when per- forming voltage conversions at 100% duty cycle with internal or external references, respectively. the differ- table 1. output data format table 2. configuration-byte format d11 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0 s0 0 0 bit 7 (msb) bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 (lsb) start 0 0 0 0 pm1 pm0 ref bit name description 7 (msb) start first logic 1 after cs goes low. (see input data format .) 6, 5, 4, 3 must be 0000 to load a configuration byte. 2, 1 pm1, pm0 these 2 bits select the desired power mode (table 4). 0 ref a logic high enables the internal reference. a logic low disables the internal reference and selects the external reference mode. table 3. conversion-byte format bit 7 (msb) bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 (lsb) start 0 1 0 sel3 sel2 sel1 sel0 bit name description 7 (msb) start first logic 1 after cs goes low. (see input data format .) 6, 5, 4 must be 010 to load a conversion byte. 3, 2, 1, 0 sel3, sel2, sel1, sel0 these 4 bits select the input configuration (table 5). figure 6. detailed sstrb timing t csh t do t sstrb t conv t sck t css csb sstrb sclk dout pdo clocked in sstrb timing
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc 16 ______________________________________________________________________________________ ence reflects the power requirement of an internal refer- ence buffer amplifier that can accommodate external loads. temperature conversions at 100% duty cycle increase supply currents to 440a (400a) through additional amplification, buffer, and bias circuitry that is otherwise inactive. place the max1298/MAX1299 in a low-current power- down state between conversions to conserve power. select standby, standby-plus, or shutdown through bits pm1 and pm0 of the initialization byte (table 4). the max1298/MAX1299 assume the shutdown power mode when v dd is first applied. standby mode standby mode turns off the max1298/MAX1299 adc, internal clock, and reference buffer amplifier. special circuitry for temperature conversions is also deactivat- ed. wake-up time is limited by the reference buffer amplifier and the associated bypass capacitor (see internal reference ). when an external reference is used, wake-up time is 0.1ms. standby-plus mode standby-plus mode is similar to the standby mode, but the internal reference output buffer remains active to shorten the wake-up time to 0.1ms for internal refer- ence mode. when using an external reference, stand- by-plus mode is equivalent to standby mode. shutdown mode shutdown mode turns off all functions other than start- up circuitry, thereby reducing typical supply current to 2a. data registers are cleared. use this power mode when interconversion times are no less than 5ms. monitoring v dd this mode of operation samples and converts the sup- ply voltage, v dd /4, which is internally generated. the reference voltage must be larger than v dd /8 for the operation to work properly. from the result of a conver- sion (code), code = 256 v dd / v ref . temperature measurements the max1298/MAX1299 perform temperature measure- ments with internal or external diode-connected transis- tors through a three-step process. first, the diode bias current changes from 31.6a to 10a to produce a temperature-dependent bias voltage difference, which is amplified by a factor of 20 and converted to digital format. second, the bias current changes from 31.6a to 100a, and the bias voltage difference is similarly amplified by a factor of 20 and converted to digital for- mat. third, the intermediate results are subtracted to achieve a digital output that is proportional to absolute temperature in degrees kelvin. the reference voltage used in conjunction with tempera- ture measurements is derived from the internal reference source to ensure that 1lsb corresponds to 1/8 of a degree. to convert to degrees celsius, subtract 273.15 from the temperature inferred from the adc output. temperature measurements require a conversion time of 2.2ms. shield output buffer the max1298/MAX1299 provide a shield output buffer voltage at sho that is approximately 0.6v (one diode drop) above v dd /2. when performing temperature measurements with an external diode, use this voltage to suppress error-producing leakage currents (see remote diode shielding ). figure 7 shows the sho out- put circuit. applications information remote diode selection temperature accuracy depends on having a good- quality, diode-connected small-signal transistor. accuracy has been experimentally verified for 2n3904 devices. cpus and other ics having on-board temper- ature-sensing diodes can also be monitored if the diode connections are floating. table 4. power-mode selection pm1 pm0 mode 0 0 shutdown 0 1 standby-plus 1 0 standby 1 1 normal operation 5 a sho v dd 2 figure 7. sho output circuit
the transistor must be a small-signal type with a base resistance less than 100 ? . tight specifications for for- ward current gain (+50 to +150, for example) indicate that the manufacturer has good process controls and that the devices have consistent v be characteristics. (see table 6 for recommended devices.) for heatsink mounting, the 500-32bt02-000 thermal sensor from fenwal electronics is a good choice. this device consists of a diode-connected transistor, an alu- minum plate with screw hole, and twisted-pair cable (fenwal inc., milford ma, 508-478-6000). twisted-pair and shielded cables for remote-sensor distances greater than 8 inches, or in particularly noisy environments, use a twisted pair. a practical length is 6 to 12 feet. for longer distances, the best solution is a shielded twisted pair such as that used for audio microphones. for example, the belden 8451 works well for distances up to 100 feet in a noisy environment. connect the shield to sho. cable resistances affect remote-sensor accuracy; 1 ? series resistance introduces +0.004 c error. remote diode shielding temperature measurements will reflect significant error if a portion of the bias current supplied to the diode anode is allowed to flow through parallel paths to ground. if the diode-connected transistor is mounted on a pc board, suppress error-producing leakage current by surrounding the collector/base leads with a metal trace that is connected to the sho shield output (figure 8). max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc ______________________________________________________________________________________ 17 sel3 sel2 sel1 sel0 positive input (in+) negative input (in-) 0000 ain0 ain5 0001 ain1 ain5 0010 ain2 ain5 0011 ain3 ain5 0100 ain4 ain5 0101 ? ? 0110 ain5 ain5 0111 internal diode anode* internal diode cathode 1000 ain0 ain1 1001 ain2 ain3 1010 ? ? 1011 v dd /4 gnd 1100 external diode 1 anode* (ain0) external diode 1 cathode (ain1) 1101 external diode 2 anode* (ain2) external diode 2 cathode (ain3) 1110 ? ? 1111 ? ? *temperature-measurement mode table 5. input selection table 6. remote-sensor transistor manufacturer manufacturer model number central semiconductor (usa) cmpt3904 fairchild semiconductor (usa) mmbt3904 motorola (usa) mmbt3904 rohm semiconductor (japan) sst3904 siemens (germany) smb3904 zetex (england) fmmt3904ct-nd
max1298/MAX1299 layout, grounding, and bypassing for best performance, use pc boards. do not use wire- wrap boards. board layout should ensure that digital and analog signal lines are separated from each other. do not run analog and digital (especially clock) signals parallel to one another or run digital lines underneath the adc package. high-frequency noise in the v dd power supply may affect adc performance. bypass the supply with a 0.1f capacitor close to pin v dd . minimize capacitor lead lengths for best supply-noise rejection. if the power supply is very noisy, connect a 10 ? resistor in series with the supply to provide lowpass filtering. definitions relative accuracy relative accuracy is the deviation of the values on an actual transfer function from a straight line. this straight line can be either a best-straight-line fit or a line drawn between the endpoints of the transfer function, once offset and gain errors have been nullified. the static lin- earity parameters for the max1298/MAX1299 are mea- sured using the best-straight-line-fit method. differential nonlinearity (dnl) differential nonlinearity is the difference between an actual step width and the ideal value of 1lsb. a dnl error specification of less than 1lsb guarantees no missing codes and a monotonic transfer function. offset error the offset error is the difference between the ideal and the actual offset points. for an adc, the offset point is the midstep value when the digital output is zero. gain error the gain or full-scale error is the difference between the ideal and actual gain points on the transfer function, after the offset error has been canceled out. for an adc, the gain point is the midstep value when the digi- tal output is full scale. aperture delay aperture delay (t ad ) is the time defined between the rising edge of the sampling clock and the instant when an actual sample is taken. chip information transistor count: 13,669 process: bicmos 12-bit serial-output temperature sensors with 5-channel adc 18 ______________________________________________________________________________________ figure 8. remote diode shielding for pc boards anode shield cathode
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc ______________________________________________________________________________________ 19 max1298 ain0 ain1 ain2 ain3 sho ain4 ain5 gnd gnd cs sclk din dout sstrb 0.1 f +5v 2n3904 2n3904 (shield) v dd typical operating circuit
max1298/MAX1299 12-bit serial-output temperature sensors with 5-channel adc maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 20 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2000 maxim integrated products printed usa is a registered trademark of maxim integrated products. maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 20 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2000 maxim integrated products printed usa is a registered trademark of maxim integrated products. maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 20 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2000 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information ssop.eps

▲Up To Search▲

Price & Availability of MAX1299

	To Download MAX1299 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .