View MAX1617AMEE12_4801351.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

remote/local temperature sensor with smbus serial interface for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maximintegrated.com max1617a evaluation kit available ________________general description the max1617a is a precise digital thermometer that reports the temperature of both a remote sensor and its own package. the remote sensor is a diode-connected transistor?ypically a low-cost, easily mounted 2n3904 npn type?hat replaces conventional thermistors or ther- mocouples. remote accuracy is ?? for multiple transis- tor manufacturers, with no calibration needed. the remote channel can also measure the die temperature of other ics, such as microprocessors, that contain an on-chip, diode-connected transistor. the 2-wire serial interface accepts standard system management bus (smbus) write byte, read byte, send byte, and receive byte commands to program the alarm thresholds and to read temperature data. the data format is 7 bits plus sign, with each bit corresponding to 1c, in two? complement format. measurements can be done automatically and autonomously, with the conversion rate programmed by the user or programmed to operate in a single-shot mode. the adjustable rate allows the user to control the supply-current drain. the max1617a is nearly identical to the popular max1617, but has improved smbus timing specifications, improved bus collision immunity, software manufacturer and device identification available via the serial interface, and a power- on reset function that can force a reset of the slave address via the serial interface. ________________________applications desktop and notebook central office computers telecom equipment smart battery packs test and measurement lan servers multichip modules industrial controls ____________________________features ? two channels: measures both remote and local temperatures ? no calibration required ? smbus 2-wire serial interface ? programmable under/overtemperature alarms ? supports smbus alert response ? supports manufacturer and device id codes ? accuracy 2? (+60? to +100?, local) 3? (-40? to +125?, local) 3? (+60? to +100?, remote) ? 3 a (typ) standby supply current ? 70 a (max) supply current in auto-convert mode ? +3v to +5.5v supply range ? small 16-pin qsop package max1617a smbclk add0 add1 v cc stby gnd alert smbdata dxp dxn interrupt to c 3v to 5.5v 200 ? 0.1 f clock 10k each data 2n3904 2200pf ___________________pin configuration 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 n.c. n.c. stby smbclk n.c. smbdata alert add0 n.c. top view max1617a qsop v cc dxp add1 dxn n.c. gnd gnd + typical operating circuit part max1617amee+ -55? to +125? temp. range pin-package 16 qsop ordering information 19-4508; rev 1; 10/12 + denotes a lead(pb)-free/rohs-compliant package.
2 remote/local temperature sensor with smbus serial interface max1617a maxim integrated absolute maximum ratings electrical characteristics (v cc = +3.3v, t a = 0? to +85? , unless otherwise noted.) (note 1) 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 cc to gnd ..............................................................-0.3v to +6v dxp, add_ to gnd ....................................-0.3v to (v cc + 0.3v) dxn to gnd ..........................................................-0.3v to +0.8v smbclk, smbdata, alert , stby to gnd ...........-0.3v to +6v smbdata, alert current .................................-1ma to +50ma dxn current .......................................................................?ma esd protection (smbclk, smbdata, alert , human body model) ......................................... 4000v esd protection (other pins, human body model)..............2000v continuous power dissipation (t a = +70?) qsop (derate 8.30mw/? above +70?) .....................667mw operating temperature range .........................-55? to +125? junction temperature ......................................................+150? storage temperature range .............................-65? to +165? lead temperature (soldering, 10sec) .............................+300? soldering temperature (reflow) .......................................+260? t a = +60? to +100? monotonicity guaranteed add0, add1; momentary upon power-on reset dxp forced to 1.5v logic inputs forced to v cc or gnd auto-convert mode from stop bit to conversion complete (both channels) v cc , falling edge t a = 0? to +85? v cc input, disables a/d conversion, rising edge auto-convert mode, average measured over 4sec. logic inputs forced to v cc or gnd. conditions ? 160 address pin bias current v 0.7 dxn source voltage ? 81012 80 100 120 remote-diode source current % -25 25 conversion rate timing error ms 94 125 156 conversion time ? 120 180 35 70 average operating supply current -2 2 bits 8 temperature resolution (note 2) ? 4 standby supply current 310 mv 50 por threshold hysteresis v 1.0 1.7 2.5 power-on reset threshold ? -3 3 initial temperature error, local diode (note 3) v 3.0 5.5 supply-voltage range v 2.60 2.80 2.95 undervoltage lockout threshold mv 50 undervoltage lockout hysteresis units min typ max parameter t r = +60? to +100? t r = -55? to +125? -3 3 ? -5 5 temperature error, remote diode (notes 3 and 4) including long-term drift -2.5 2.5 ? -3.5 3.5 temperature error, local diode (notes 2 and 3) 0.25 conv/sec 2.0 conv/sec t a = +60? to +100? t a = 0? to +85? high level low level adc and power supply smbus static hardware or software standby, smbclk at 10khz
3 remote/local temperature sensor with smbus serial interface max1617a maxim integrated electrical characteristics (continued) (v cc = +3.3v, t a = 0? to +85? , unless otherwise noted.) (note 1) stby , smbclk, smbdata; v cc = 3v to 5.5v t high , 90% to 90% points t low , 10% to 10% points (note 5) smbclk, smbdata logic inputs forced to v cc or gnd alert forced to 5.5v stby , smbclk, smbdata; v cc = 3v to 5.5v alert, smbdata forced to 0.4v conditions ? 4 smbclk clock high time ? 4.7 smbclk clock low time khz dc 100 smbus clock frequency pf 5 smbus input capacitance ? -1 1 logic input current ? 1 alert output high leakage current v 2.2 logic input high voltage v 0.8 logic input low voltage ma 6 logic output low sink current units min typ max parameter t su:dat , 10% or 90% of smbdata to 10% of smbclk t su:sto , 90% of smbclk to 10% of smbdata t hd:sta , 10% of smbdata to 90% of smbclk t su:sta , 90% to 90% points ns 250 smbus data valid to smbclk rising-edge time ? 4 smbus stop-condition setup time ? 4 smbus start-condition hold time ns 500 smbus repeated start-condition setup time ? 4.7 smbus start-condition setup time t hd:dat (note 6) ? 0 smbus data-hold time master clocking in data ? 1 smbclk falling edge to smbus data-valid time smbus interface electrical characteristics (v cc = +3.3v, t a = -55? to +125? , unless otherwise noted.) (note 1) conditions monotonicity guaranteed t a = +60? to +100? bits 8 temperature resolution (note 2) -2 2 t r = +60? to +100? t a = -55? to +125? ? -3 3 initial temperature error, local diode (note 3) v 3.0 5.5 supply-voltage range from stop bit to conversion complete (both channels) auto-convert mode ms 94 125 156 conversion time % -25 25 conversion rate timing error -3 3 t r = -55? to +125? ? units min typ max -5 5 parameter temperature error, remote diode (notes 3 and 4) adc and power supply
0 6 3 9 12 50 5k 500k 50k 5m 500 50m temperature error vs. power-supply noise frequency max1617atoc04 frequency (hz) temperature error (?) v in = square wave applied to v cc with no 0.1 f v cc capacitor v in = 250mvp-p remote diode v in = 250mvp-p local diode v in = 100mvp-p remote diode -20 -10 0 10 20 11030 3100 temperature error vs. pc board resistance max1617atoc01 leakage resistance (m ? ) temperature error (?) path = dxp to v cc (5v) path = dxp to gnd -2 -1 0 1 2 -50 50 100 0150 temperature error vs. remote-diode temperature max1617atoc02 temperature (?) temperature error (?) samsung kst3904 motorola mmbt3904 zetex fmmt3904 random samples __________________________________________typical operating characteristics (t a = +25?, unless otherwise noted.) 4 remote/local temperature sensor with smbus serial interface max1617a maxim integrated electrical characteristics (continued) (v cc = +3.3v, t a = -55? to +125? , unless otherwise noted.) (note 1) note 1: all devices 100% production tested at t a = +85?. limits over temperature are guaranteed by design. note 2: guaranteed but not 100% tested. note 3: quantization error is not included in specifications for temperature accuracy. for example, if the max1617a device temper- ature is exactly +66.7?, the adc may report +66?, +67?, or +68? (due to the quantization error plus the +1/2? offset used for rounding up) and still be within the guaranteed ?? error limits for the +60? to +100? temperature range (table 2). note 4: a remote diode is any diode-connected transistor from table 1. t r is the junction temperature of the remote diode. see remote diode selection for remote diode forward voltage requirements. note 5: the smbus logic block is a static design that works with clock frequencies down to dc. while slow operation is possible, it violates the 10khz minimum clock frequency and smbus specifications, and may monopolize the bus. note 6: note that a transition must internally provide at least a hold time in order to bridge the undefined region (300ns max) of smbclk? falling edge. conditions units min typ max parameter stby , smbclk, smbdata 2.2 logic input high voltage v 2.4 stby , smbclk, smbdata; v cc = 3v to 5.5v v 0.8 logic input low voltage alert forced to 5.5v ? 1 alert output high leakage current logic inputs forced to v cc or gnd ? -2 2 logic input current v cc = 3v v cc = 5.5v alert, smbdata forced to 0.4v ma 6 logic output low sink current smbus interface
5 remote/local temperature sensor with smbus serial interface max1617a maxim integrated 0 10 20 30 50 5k 500k 50k 5m 500 50m temperature error vs. common-mode noise frequency max1617atoc05 frequency (hz) temperature error (?) v in = square wave ac coupled to dxn v in = 100mvp-p v in = 50mvp-p v in = 25mvp-p -5 5 0 10 50 5k 500k 50k 5m 500 50m temperature error vs. differential-mode noise frequency max1617atoc06 frequency (hz) temperature error (?) v in = 10mvp-p square wave applied to dxp-dxn 0 10 20 04060 80 20 100 temperature error vs. dxp?xn capacitance max1617atoc07 dxp?xn capacitance (nf) temperature error (?) v cc = 5v 0 100 400 200 300 500 01 0.0625 4 0.25 2 0.125 0.5 8 operating supply current vs. conversion rate max1617atoc10 conversion rate (hz) supply current ( a) v cc = 5v averaged measurements 0 5 15 25 10 20 30 35 1k 100k 10k 1000k standby supply current vs. clock frequency max1617atoc08 smbclk frequency (hz) supply current ( a) v cc = 5v v cc = 3.3v smbclk is driven rail-to-rail 0 3 60 6 20 100 03 14 25 standby supply current vs. supply voltage max1617atoc09 supply voltage (v) supply current ( a) add0, add1 = gnd add0, add1 = high-z 0 25 100 50 75 125 -2 8 04 2610 response to thermal shock max1617atoc11 time (sec) temperature (?) 16-qsop immersed in +115? fluorinert bath ____________________________typical operating characteristics (continued) (t a = +25?, unless otherwise noted.) -5 0 5 50 5k 500k 50k 5m 500 50m temperature error vs. differential-mode noise frequency max1617atoc03 frequency (hz) temperature error (?) v in = 3mvp-p square wave applied to dxp-dxn
6 remote/local temperature sensor with smbus serial interface max1617a maxim integrated pin description general description the max1617a is a temperature sensor designed to work in conjunction with an external microcontroller (?) or other intelligence in thermostatic, process-con- trol, or monitoring applications. the ? is typically a power-management or keyboard controller, generating smbus serial commands by ?it-banging?general-pur- pose input/output (gpio) pins or via a dedicated smbus interface block. essentially an 8-bit serial analog-to-digital converter (adc) with a sophisticated front end, the max1617a contains a switched current source, a multiplexer, an adc, an smbus interface, and associated control logic (figure 1). temperature data from the adc is loaded into two data registers, where it is automatically com- pared with data previously stored in four over/under- temperature alarm registers. adc and multiplexer the adc is an averaging type that integrates over a 60ms period (each channel, typical) with excellent noise rejection. the multiplexer automatically steers bias currents through the remote and local diodes, measures their forward voltages, and computes their temperatures. both channels are automatically converted once the conversion process has started, either in free-running or single-shot mode. if one of the two channels is not used, the device still performs both measurements, and the user can simply ignore the results of the unused channel. if the remote diode channel is unused, tie dxp to dxn rather than leaving the pins open. the dxn input is biased at 0.65v(typ) above ground by an internal diode to set up the analog-to-digital (a/d) inputs for a differential measurement. the typical dxp?xn differential input voltage range is 0.25v to 0.95v. to ensure proper operation over full temperature range, ensure v dxp (0.78 x v cc - 1.1) volts. smbus serial-data input/output, open drain smbdata 12 smbus serial-clock input smbclk 14 hardware standby input. temperature and comparison threshold data are retained in standby mode. low = standby mode, high = operate mode. stby 15 smbus address select pin (table 8). add0 and add1 are sampled upon power-up. excess capacitance (>50pf) at the address pins when unconnected may cause address-recognition problems. add1 6 ground gnd 7, 8 smbus slave address select pin add0 10 smbus alert (interrupt) output, open drain alert 11 combined current sink and a/d negative input. dxn is normally biased to a diode voltage above ground. dxn 4 combined current source and a/d positive input for remote-diode channel. do not leave dxp uncon- nected; tie dxp to dxn if no remote diode is used. place a 2200pf capacitor between dxp and dxn for noise filtering. dxp 3 pin supply voltage input, 3v to 5.5v. bypass to gnd with a 0.1? capacitor. a 200 ? series resistor is recom- mended but not required for additional noise filtering. v cc 2 no connection. not internally connected. may be used for pc board trace routing. n.c. 1, 5, 9, 13, 16 function name
7 remote/local temperature sensor with smbus serial interface max1617a maxim integrated figure 1. functional diagram remote mux local remote temperature data register high-temperature threshold (remote t high ) low-temperature threshold (remote t low ) digital comparator (remote) local temperature data register high-temperature threshold (local t high) low-temperature threshold (local t low ) digital comparator (local) command byte (index) register smbdata smbclk address decoder read write control logic smbus add1 add0 stby status byte register configuration byte register conversion rate register alert response address register selected via slave add = 0001 100 adc + diode fault dxp dxn gnd v cc - + + - 8 8 8 8 8 8 88 2 7 alert qs r max1617a
excess resistance in series with the remote diode caus- es about +1/2? error per ohm. likewise, 200? of off- set voltage forced on dxp?xn causes about 1c error. a/d conversion sequence if a start command is written (or generated automatical- ly in the free-running auto-convert mode), both channels are converted, and the results of both measurements are available after the end of conversion. a busy status bit in the status byte shows that the device is actually performing a new conversion; however, even if the adc is busy, the results of the previous conversion are always available. remote-diode selection temperature accuracy depends on having a good-qual- ity, diode-connected small-signal transistor. see table 1 for a recommended list of diode-connected small-signal transistors. the max1617a can also directly measure the die temperature of cpus and other integrated cir- cuits having on-board temperature-sensing diodes. the transistor must be a small-signal type with a rela- tively high forward voltage; otherwise, the a/d input voltage range can be violated. the forward voltage must be greater than 0.25v at 10?; check to ensure this is true at the highest expected temperature. the forward voltage (v dxp - v dxn ) must be less than 0.95v at 100?; additionally, ensure the maximum v dxp (dxp voltage) (0.78 x v cc - 1.1) volts over your expected range of temperature. large power transistors don? work at all. also ensure that the base resistance is less than 100 ? . tight specifications for forward-current gain (+50 to +150, for example) indicate that the manufac- turer has good process controls and that the devices have consistent vbe characteristics. 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 aluminum plate with screw hole, and twisted-pair cable (fenwal inc., milford, ma, 508-478-6000). thermal mass and self-heating thermal mass can seriously degrade the max1617a? effective accuracy. the thermal time constant of the qsop-16 package is about 140sec in still air. for the max1617a junction temperature to settle to within +1? after a sudden +100? change requires about five time constants or 12 minutes. the use of smaller packages for remote sensors, such as sot23s, improves the situ- ation. take care to account for thermal gradients between the heat source and the sensor, and ensure that stray air currents across the sensor package do not interfere with measurement accuracy. self-heating does not significantly affect measurement accuracy. remote-sensor self-heating due to the diode current source is negligible. for the local diode, the worst-case error occurs when auto-converting at the fastest rate and simultaneously sinking maximum cur- rent at the alert output. for example, at an 8hz rate and with alert sinking 1ma, the typical power dissi- pation is v cc 450? plus 0.4v 1ma. package theta j-a is about 150?/w, so with v cc = 5v and no copper pc board heatsinking, the resulting temperature rise is: dt = 2.7mw 150?/w = 0.4? even with these contrived circumstances, it is difficult to introduce significant self-heating errors. adc noise filtering the adc is an integrating type with inherently good noise rejection, especially of low-frequency signals such as 60hz/120hz power-supply hum. micropower opera- tion places constraints on high-frequency noise rejection; therefore, careful pc board layout and proper external noise filtering are required for high-accuracy remote measurements in electrically noisy environments. high-frequency emi is best filtered at dxp and dxn with an external 2200pf capacitor. this value can be increased to about 3300pf (max), including cable capacitance. higher capacitance than 3300pf intro- duces errors due to the rise time of the switched cur- rent source. nearly all noise sources tested cause the adc measure- ments to be higher than the actual temperature, typically by +1? to +10?, depending on the frequency and amplitude (see typical operating characteristics ). 8 remote/local temperature sensor with smbus serial interface max1617a maxim integrated cmpt3904 central semiconductor (usa) mmbt3904 motorola (usa) mmbt3904 sst3904 rohm semiconductor (japan) kst3904-tf samsung (korea) fmmt3904ct-nd zetex (england) manufacturer model number smbt3904 siemens (germany) table 1. remote-sensor transistor manufacturers note : transistors must be diode-connected (base shorted to collector). national semiconductor (usa)
pc board layout 1) place the max1617a as close as practical to the remote diode. in a noisy environment, such as a computer motherboard, this distance can be 4 in. to 8 in. (typical) or more as long as the worst noise sources (such as crts, clock generators, memory buses, and isa/pci buses) are avoided. 2) do not route the dxp?xn lines next to the deflec- tion coils of a crt. also, do not route the traces across a fast memory bus, which can easily intro- duce +30? error, even with good filtering. otherwise, most noise sources are fairly benign. 3) route the dxp and dxn traces in parallel and in close proximity to each other, away from any high- voltage traces such as +12v dc . leakage currents from pc board contamination must be dealt with carefully, since a 20m ? leakage path from dxp to ground causes about +1? error. 4) connect guard traces to gnd on either side of the dxp?xn traces (figure 2). with guard traces in place, routing near high-voltage traces is no longer an issue. 5) route through as few vias and crossunders as possi- ble to minimize copper/solder thermocouple effects. 6) when introducing a thermocouple, make sure that both the dxp and the dxn paths have matching thermocouples. in general, pc board-induced ther- mocouples are not a serious problem. a copper-sol- der thermocouple exhibits 3v/?, and it takes about 200? of voltage error at dxp?xn to cause a +1? measurement error. so, most parasitic ther- mocouple errors are swamped out. 7) use wide traces. narrow ones are more inductive and tend to pick up radiated noise. the 10 mil widths and spacings recommended in figure 2 aren? absolutely necessary (as they offer only a minor improvement in leakage and noise), but try to use them where practical. 8) keep in mind that copper can? be used as an emi shield, and only ferrous materials, such as steel, work well. placing a copper ground plane between the dxp-dxn traces and traces carrying high-frequency noise signals does not help reduce emi. pc board layout checklist place the max1617a close to a remote diode. keep traces away from high voltages (+12v bus). keep traces away from fast data buses and crts. use recommended trace widths and spacings. place a ground plane under the traces. use guard traces flanking dxp and dxn and con- necting to gnd. place the noise filter and the 0.1? v cc bypass capacitors close to the max1617a. add a 200 ? resistor in series with v cc for best noise filtering (see typical operating circuit ). twisted pair and shielded cables for remote-sensor distances longer than 8 in., or in par- ticularly noisy environments, a twisted pair is recom- mended. its practical length is 6 feet to 12 feet (typical) before noise becomes a problem, as tested in a noisy electronics laboratory. for longer distances, the best solution is a shielded twisted pair like that used for audio microphones. for example, the belden 8451 works well for distances up to 100 feet in a noisy environment. connect the twisted pair to dxp and dxn and the shield to gnd, and leave the shield? remote end unterminated. excess capacitance at dx_ limits practical remote sen- sor distances (see typical operating characteristics ). for very long cable runs, the cable? parasitic capaci- tance often provides noise filtering, so the 2200pf capacitor can often be removed or reduced in value. cable resistance also affects remote-sensor accuracy; 1 ? series resistance introduces about +1/2? error. low-power standby mode standby mode disables the adc and reduces the sup- ply-current drain to less than 10?. enter standby mode by forcing the stby pin low or via the run/stop bit in the configuration byte register. hardware and software standby modes behave almost identically: all data is retained in memory, and the smb interface is alive and listening for reads and writes. the only differ- ence is that in hardware standby mode, the one-shot command does not initiate a conversion. standby mode is not a shutdown mode. with activity on the smbus, extra supply current is drawn (see typical operating characteristics ). in software standby mode, 9 remote/local temperature sensor with smbus serial interface max1617a maxim integrated minimum 10 mils 10 mils 10 mils 10 mils gnd dxn dxp gnd figure 2. recommended dxp/dxn pc traces
the max1617a can be forced to perform a/d conver- sions via the one-shot command, despite the run/stop bit being high. activate hardware standby mode by forcing the stby pin low. in a notebook computer, this line may be con- nected to the system sustat# suspend-state signal. the stby pin low state overrides any software conversion command. if a hardware or software standby command is received while a conversion is in progress, the conversion cycle is truncated, and the data from that conversion is not latched into either temperature reading register. the previ- ous data is not changed and remains available. supply-current drain during the 125ms conversion peri- od is always about 450?. slowing down the conver- sion rate reduces the average supply current (see typical operating characteristics ). between conver- sions, the instantaneous supply current is about 25? due to the current consumed by the conversion rate timer. in standby mode, supply current drops to about 3?. at very low supply voltages (under the power-on- reset threshold), the supply current is higher due to the address pin bias currents. it can be as high as 100?, depending on add0 and add1 settings. smbus digital interface from a software perspective, the max1617a appears as a set of byte-wide registers that contain temperature data, alarm threshold values, or control bits. a standard smbus 2-wire serial interface is used to read tempera- ture data and write control bits and alarm threshold data. each a/d channel within the device responds to the same smbus slave address for normal reads and writes. the max1617a employs four standard smbus protocols: write byte, read byte, send byte, and receive byte (figure 3). the shorter receive byte protocol allows quicker transfers, provided that the correct data register was previously selected by a read byte instruction. use caution with the shorter protocols in multi-master systems, since a second master could overwrite the command byte without informing the first master. the temperature data format is 7 bits plus sign in two? complement form for each channel, with each data bit rep- resenting 1? (table 2), transmitted msb first. measure- ments are off set by +1/2? to minimize internal rounding errors; for example, +99.6c is reported as +100?. max1617a 10 remote/local temperature sensor with smbus serial interface max1617a maxim integrated ack 7 bits address ack wr 8 bits data ack 1 p 8 bits s command write byte format read byte format send byte format receive byte format slave address: equiva- lent to chip-select line of a 3-wire interface command byte: selects which register you are writing to data byte: data goes into the register set by the command byte (to set thresholds, configuration masks, and sampling rate) ack 7 bits address ack wr s ack 8 bits data 7 bits address rd 8 bits /// p s command slave address: equiva- lent to chip-select line command byte: selects which register you are reading from slave address: repeated due to change in data- flow direction data byte: reads from the register set by the command byte ack 7 bits address wr 8 bits command ack p s ack 7 bits address rd 8 bits data /// p s command byte: sends com- mand with no data, usually used for one-shot command data byte: reads data from the register commanded by the last read byte or write byte transmission; also used for smbus alert response return address s = start condition shaded = slave transmission p = stop condition /// = not acknowledged figure 3. smbus protocols
alarm threshold registers four registers store alarm threshold data, with high- temperature (t high ) and low-temperature (t low ) reg- isters for each a/d channel. if either measured temperature equals or exceeds the corresponding alarm threshold value, an alert interrupt is asserted. the power-on-reset (por) state of both t high registers is full scale (0111 1111, or +127?). the por state of both t low registers is 1100 1001 or -55?. diode fault alarm there is a continuity fault detector at dxp that detects whether the remote diode has an open-circuit condi- tion. at the beginning of each conversion, the diode fault is checked, and the status byte is updated. this fault detector is a simple voltage detector; if dxp rises above v cc - 1v (typical) due to the diode current source, a fault is detected. note that the diode fault isn? checked until a conversion is initiated, so immedi- ately after power-on reset the status byte indicates no fault is present, even if the diode path is broken. if the remote channel is shorted (dxp to dxn or dxp to gnd), the adc reads 0000 0000 so as not to trip either the t high or t low alarms at their por settings. in applications that are never subjected to 0? in normal operation, a 0000 0000 result can be checked to indi- cate a fault condition in which dxp is accidentally short circuited. similarly, if dxp is short circuited to v cc , the adc reads +127? for both remote and local channels, and the device alarms. a a l l e e r r t t interrupts the alert interrupt output signal is latched and can only be cleared by reading the alert response address. interrupts are generated in response to t high and t low comparisons and when the remote diode is disconnect- ed (for continuity fault detection). the interrupt does not halt automatic conversions; new temperature data con- tinues to be available over the smbus interface after alert is asserted. the interrupt output pin is open-drain so that devices can share a common interrupt line. the interrupt rate can never exceed the conversion rate. the interface responds to the smbus alert response address, an interrupt pointer return-address feature (see alert response address section). prior to taking corrective action, always check to ensure that an inter- rupt is valid by reading the current temperature. alert response address the smbus alert response interrupt pointer provides quick fault identification for simple slave devices that lack the complex, expensive logic needed to be a bus master. upon receiving an alert interrupt signal, the host master can broadcast a receive byte transmission to the alert response slave address (0001 100). then any slave device that generated an interrupt attempts to identify itself by putting its own address on the bus (table 3). 11 remote/local temperature sensor with smbus serial interface max1617a maxim integrated digital output data bits 0 111 1111 +127 +127.00 0 111 1111 0 111 1110 +126 +126.00 +127 +126.50 0 001 1001 0 000 0001 +1 +0.50 0 000 0000 0 000 0000 0 0.00 rounded temp. (?) temp. (?) 0 +0.25 +25 +25.25 0 000 0000 0 000 0000 0 -0.50 1 111 1111 1 111 1111 -1 -1.00 -1 -0.75 1 110 0111 1 110 0110 -26 -25.50 1 100 1001 1 100 1001 -55 -55.00 0 -0.25 -55 -54.75 -25 -25.00 1 011 1111 1 011 1111 -65 -70.00 -65 -65.00 table 2. data format (two? complement) table 3. read format for alert response address (0001100) add6 6 provide the current max1617a slave address that was latched at por (table 8) function add5 5 add4 4 add3 3 add2 2 add1 1 add7 7 (msb) 1 0 (lsb) logic 1 bit name sign msb lsb 0 111 1111 +127 +130.00
the alert response can activate several different slave devices simultaneously, similar to the i 2 c general call. if more than one slave attempts to respond, bus arbitra- tion rules apply, and the device with the lower address code wins. the losing device does not generate an acknowledge and continues to hold the alert line low until serviced (implies that the host interrupt input is level-sensitive). successful reading of the alert response address clears the interrupt latch. command byte functions the 8-bit command byte register (table 4) is the master index that points to the various other registers within the max1617a. the register? por state is 0000 0000, so that a receive byte transmission (a protocol that lacks the command byte) that occurs immediately after por returns the current local temperature data. the one-shot command immediately forces a new conver- sion cycle to begin. in software standby mode (run/stop bit = high), a new conversion is begun, after which the device returns to standby mode. if a conversion is in progress when a one-shot command is received, the command is ignored. if a one-shot command is received in auto-convert mode (run/stop bit = low) between con- versions, a new conversion begins, the conversion rate timer is reset, and the next automatic conversion takes place after a full delay elapses. configuration byte functions the configuration byte register (table 5) is used to mask (disable) interrupts and to put the device in soft- ware standby mode. the lower six bits are internally set to (xx1111), making them ?on? care?bits. write zeros to these bits. this register? contents can be read back over the serial interface. status byte functions the status byte register (table 6) indicates which (if any) temperature thresholds have been exceeded. this byte also indicates whether or not the adc is convert- ing and whether there is an open circuit in the remote diode dxp?xn path. after por, the normal state of all the flag bits is zero, assuming none of the alarm condi- tions are present. the status byte is cleared by any successful read of the status byte, unless the fault per- 12 remote/local temperature sensor with smbus serial interface max1617a maxim integrated table 4. command-byte bit assignments * if the device is in hardware standby mode at por, both temperature registers read 0?. read remote temperature: returns latest temperature rrte 01h 00h command 0000 0000* 0000 0000* por state read configuration byte rcl 03h 02h 0000 0000 n/a read status byte (flags, busy signal) rsl read local t high limit rlhn 05h read local temperature: returns latest temperature rlts 04h 0111 1111 0000 0010 read remote t high limit rrhi 07h 06h 0111 1111 1100 1001 read local t low limit rlli read conversion rate byte register rcra write configuration byte wca 09h 08h n/a 1100 1001 function write local t high limit wlho 0bh 0ah n/a n/a write conversion rate byte wcrw write remote t high limit wrha 0dh read remote t low limit rrls 0ch n/a n/a one-shot command (use send-byte format) osht 0fh 0eh n/a n/a write remote t low limit wrln write local t low limit wllm write software por spor fch n/a read device id code devid ffh feh 00000001 0100 1101 read manufacturer id code mfgid
sists. note that the alert interrupt latch is not auto- matically cleared when the status flag bit is cleared. when auto-converting, if the t high and t low limits are close together, it? possible for both high-temp and low- temp status bits to be set, depending on the amount of time between status read operations (especially when converting at the fastest rate). in these circumstances, it? best not to rely on the status bits to indicate rever- sals in long-term temperature changes and instead use a current temperature reading to establish the trend direction. conversion rate byte the conversion rate register (table 7) programs the time interval between conversions in free-running auto-convert mode. this variable rate control reduces the supply cur- rent in portable-equipment applications. the conversion rate byte? por state is 02h (0.25hz). the max1617a looks only at the 3 lsb bits of this register, so the upper 5 bits are ?on? care?bits, which should be set to zero. the conversion rate tolerance is ?5% at any rate setting. valid a/d conversion results for both channels are avail- able one total conversion time (125ms nominal, 156ms maximum) after initiating a conversion, whether conver- sion is initiated via the run/stop bit, hardware stby pin, one-shot command, or initial power-up. changing the conversion rate can also affect the delay until new results are available (table 8). manufacturer and device id codes two rom registers provide manufacturer and device id codes (table 4). reading the manufacturer id returns 4dh, which is the ascii code ??(for maxim). reading the device id returns 01h, indicating a max1617a device. if read word 16-bit smbus protocol is employed (rather than the 8-bit read byte), the least significant byte contains the data and the most signifi- cant byte contains 00h in both cases. slave addresses the max1617a appears to the smbus as one device having a common address for both adc channels. the device address can be set to one of nine different val- ues by pin-strapping add0 and add1 so that more than one max1617a can reside on the same bus with- out address conflicts (table 9). 13 remote/local temperature sensor with smbus serial interface max1617a maxim integrated run/ stop 6 0 0 por state standby mode control bit. if high, the device immediately stops con- verting and enters stand- by mode. if low, the device converts in either one-shot or timer mode. masks all alert inter- rupts when high. function rfu 5? 0 reserved for future use mask 7 (msb) bit name table 5. configuration-byte bit assignments table 7. conversion-rate control byte table 6. status-byte bit assignments * these flags stay high until cleared by por, or until the status byte register is read. lhigh* 6 a high indicates that the local high- temperature alarm has activated. a high indicates that the adc is busy converting. function llow* 5 a high indicates that the local low- temperature alarm has activated. rhigh* 4 a high indicates that the remote high- temperature alarm has activated. rlow* 3 a high indicates that the remote low- temperature alarm has activated. open* 2 a high indicates a remote-diode conti- nuity (open-circuit) fault. rfu 1 busy 7 (msb) reserved for future use (returns 0) rfu 0 (lsb) reserved for future use (returns 0) bit name 0.125 01h 33 30 0.25 02h 35 0.5 03h 48 1 04h 70 2 05h 128 4 06h 0.0625 00h 225 8 07h 425 rfu 08h to ffh data conversion rate (hz) average supply current (a typ, at v cc = 3.3v)
14 remote/local temperature sensor with smbus serial interface max1617a maxim integrated the address pin states are checked at por and spor only, and the address data stays latched to reduce qui- escent supply current due to the bias current needed for high-z state detection. the max1617a also responds to the smbus alert response slave address (see the alert response address section). por and uvlo the max1617a has a volatile memory. to prevent ambig- uous power-supply conditions from corrupting the data in memory and causing erratic behavior, a por voltage detector monitors v cc and clears the memory if v cc falls below 1.7v (typical, see electrical characteristics table). when power is first applied and v cc rises above 1.75v (typical), the logic blocks begin operating, although reads and writes at v cc levels below 3v are not recommended. a second v cc comparator, the adc uvlo comparator, prevents the adc from converting until there is sufficient headroom (v cc = 2.8v typical). the spor software por command can force a power-on reset of the max1617a registers via the serial interface. use the send byte protocol with command = fch. this is most commonly used to reconfigure the slave address of the max1617a ?n the fly,?where external hardware has forced new states at the add0 and add1 address pins prior to the software por. the new address takes effect less than 100? after the spor transmission stop condition. power-up defaults: ? interrupt latch is cleared. ? address select pins are sampled. ? adc begins auto-converting at a 0.25hz rate. ? command byte is set to 00h to facilitate quick remote receive byte queries. ? t high and t low registers are set to max and min limits, respectively. table 8. rlts and rrte temp register update timing chart n/a (0.25hz) new conversion rate (changed via write to wcrw) power-on reset auto-convert operating mode conversion initiated by: 156ms max time until rlts and rrte are updated 156ms max n/a 1-shot command, while idling between automatic conversions auto-convert when current conversion is complete (1-shot is ignored) 20sec n/a 0.0625hz rate timer auto-convert 1-shot command that occurs during a conversion auto-convert 10sec 5sec 0.125hz 0.25hz rate timer auto-convert 2.5sec 1.25sec 0.5hz 1hz rate timer auto-convert rate timer auto-convert rate timer auto-convert 625ms 312.5ms 2hz 4hz rate timer auto-convert 237.5ms 156ms 8hz n/a stby pin hardware standby rate timer auto-convert rate timer auto-convert 156ms 156ms n/a n/a 1-shot command software standby run/stop bit software standby table 9. slave address decoding (add0 and add1) note: high-z means that the pin is left unconnected. 0011 001 high-z gnd 0011 000 address 0101 001 gnd high-z 0011 010 v cc gnd 0101 011 v cc high-z 0101 010 1001 101 high-z v cc 1001 100 gnd gnd gnd v cc high-z high-z 1001 110 v cc v cc add0 add1
15 remote/local temperature sensor with smbus serial interface max1617a maxim integrated figure 5. smbus read timing diagram figure 4. smbus write timing diagram smbclk ab cd e fg h i j k smbdata t su:sta t hd:sta t low t high t su:dat t hd:dat t su:sto t buf a = start condition b = msb of address clocked into slave c = lsb of address clocked into slave d = r/w bit clocked into slave e = slave pulls smbdata line low l m f = acknowledge bit clocked into master g = msb of data clocked into slave h = lsb of data clocked into slave i = slave pulls smbdata line low j = acknowledge clocked into master k = acknowledge clock pulse l = stop condition, data executed by slave m = new start condition smbclk a = start condition b = msb of address clocked into slave c = lsb of address clocked into slave d = r/w bit clocked into slave ab cd e fg h i j smbdata t su:sta t hd:sta t low t high t su:dat t su:sto t buf k e = slave pulls smbdata line low f = acknowledge bit clocked into master g = msb of data clocked into master h = lsb of data clocked into master i = acknowledge clock pulse j = stop condition k = new start condition
16 remote/local temperature sensor with smbus serial interface max1617a maxim integrated listing 1. pseudocode example
17 remote/local temperature sensor with smbus serial interface max1617a maxim integrated listing 1. pseudocode example (continued) programming example: clock-throttling control for cpus listing 1 gives an untested example of pseudocode for proportional temperature control of intel mobile cpus via a power-management microcontroller. this program consists of two main parts: an initialization routine and an interrupt handler. the initialization routine checks for smbus communications problems and sets up the max1617a configuration and conversion rate. the interrupt handler responds to alert signals by reading the current temperature and setting a cpu clock duty factor proportional to that temperature. the relationship between clock duty and temperature is fixed in a look- up table contained in the microcontroller code. note: thermal management decisions should be made based on the latest temperature obtained from the max1617a rather than the value of the status byte. the max1617a responds very quickly to changes in its environment due to its sensitivity and its small thermal mass. high and low alarm conditions can exist in the status byte due to the max1617a correctly reporting environmental changes around it.
18 remote/local temperature sensor with smbus serial interface max1617a maxim integrated listing 1. pseudocode example (continued)
19 remote/local temperature sensor with smbus serial interface max1617a maxim integrated package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.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 per tains to the package regardless of rohs status. package type package code outline no. land pattern no. 16 qsop e116+1 21-0055 90-0167
maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integr ated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and specifications without notice at any tim e. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. 20 maxim integrated 160 rio robles, san jose, ca 95134 usa 1-408-601-1000 2012 maxim integrated products, inc. maxim integrated and the maxim integrated logo aretradmarks of maxim integrated products, inc. remote/local temperature sensor with smbus serial interface max1617a revision history revision number revision date description pages changed 0 1/99 initial release 1 10/12 updated electrical characteristics tables (added new note 1); updated adc and multiplexer and remote-diode selection sections 2?, 6, 8

▲Up To Search▲

Price & Availability of MAX1617AMEE12

	To Download MAX1617AMEE12 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .