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general description the max6657/max6658/max6659 are precise, two-channel digital temperature sensors. each accurately measures the temperature of its own die and one remote pn junction, and reports the temperature in digi- tal form on a 2-wire serial interface. the remote junction can be a diode-connected transistor like the low-cost npn type 2n3904 or 2n3906 pnp type. the remote junction can also be a common-collector pnp, such as a substrate pnp of a microprocessor. the 2-wire serial interface accepts standard system management bus (smbus) commands such as write byte, read byte, send byte, and receive byte to read the temperature data and program the alarm thresholds and conversion rate. the max6657/max6658/ max6659 can function autonomously with a program- mable conversion rate, which allows the control of sup- ply current and temperature update rate to match system needs. for conversion rates of 4hz or less, the temperature is represented in extended mode as 10 bits + sign with a resolution of 0.125?. when the con- version rate is faster than 4hz, output data is 7 bits + sign with a resolution of 1?. the max6657/ max6658/max6659 also include an smbus timeout feature to enhance system reliability. remote accuracy is ?? between +60? and +100? with no calibration needed. the max6657 measures temperatures from 0? to +125? and the max6658/ max6659 from -55? to +125?. the max6659 has the added benefit of being able to select one of three addresses through an address pin, and a second over- temperature alarm pin for greater system reliability. applications desktop computers workstations notebook computers servers features ? dual channel measures remote and local temperature ? 11-bit, +0.125c resolution ? high accuracy 1c (max) from +60c to +100c (remote) ? no calibration required ? programmable under/overtemperature alarms ? programmable conversion rate (0.0625hz to 16hz) ? smbus/i 2 c-compatible interface ? two alarm outputs: alert and overt1 (max6657 and max6658) ? three alarm outputs: alert , overt1 , and overt2 (max6659) ? compatible with 65nm process technology (y versions) max6657/max6658/max6659 ??, smbus-compatible remote/local temperature sensors with overtemperature alarms ___________________________________________________ _____________ maxim integrated products 1 19-2034; rev 5; 10/10 ordering information part measured temp range pin-package max6657 msa 0? to +125? 8 so max6657msa+ 0? to +125? 8 so max6657msa-t 0? to +125? 8 so max6657msa+t 0? to +125? 8 so MAX6657YMSA+ 0? to +125? 8 so MAX6657YMSA+t 0? to +125? 8 so smbus is a trademark of intel corp. 1615 14 13 12 11 10 9 12 34 5 6 7 8 v cc n.c.stby smbclk n.c. smbdata n.c. overt2 alert top view max6659 qsop n.c.dxp overt1 dxnadd gndgnd alert gnd overt1 12 8 7 smbclk smbdata dxp dxn v cc so 3 4 6 5 max6657max6658 pin configurations for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. typical operating circuit appears at the end of the data sheet. ordering information continued at end of data sheet. note: all devices are specified over the -55? to +125? oper- ating temperature range. + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. downloaded from: http:///
max6657/max6658/max6659 2 __________________________________________________ _____________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. (all voltages referenced to gnd.)v cc ..........................................................................-0.3v to +6v dxp ............................................................-0.3v to (v cc + 0.3v) dxn ......................................................................-0.3v to +0.8v smbclk, smbdata, alert , overt1 , overt2 ..............................................................-0.3v to +6v smbdata, alert , overt1 , overt2 current ..........................................................-1ma to +50ma dxn current ......................................................................?ma continuous power dissipation (t a = +70?) 8-pin so (derate 5.9mw/? above +70?) .................471mw 16-pin qsop (derate 8.3mw/? above +70?) ..........664mw junction temperature .....................................................+150? storage temperature range ............................-65? to +150? lead temperature (soldering, 10s) ................................+300? soldering temperature (reflow) lead(pb)-free ..............................................................+260? containing lead(pb) ....................................................+240? electrical characteristics (v cc = +3.0v to +5.5v, t a = 0? to +125?, unless otherwise specified. typical values are at v cc = +3.3v and t a = +25?.) parameter symbol conditions min typ max units 1 c temperature resolution,legacy mode 8 bits 0.125 ? temperature resolution,extended mode 11 bits t rj = +60? to +100?, v cc = +3.3v (note 1) -1.0 +1.0 t rj = 0? to +100?, v cc = +3.3v (note 1) -3.0 +3.0 remote temperature error(max6657, max6657y) t rj = 0? to +125?, v cc = +3.3v (note 1) -5.0 +5.0 ? t a = +60? to +100?, v cc = +3.3v -2.0 +2.0 t a = 0? to +100?, v cc = +3.3v -3.0 +3.0 local temperature error(max6657) t a = 0? to +125?, v cc = +3.3v -5.0 +5.0 ? t rj = +60? to +100?, v cc = +3.3v (note 1) -1.0 1.0 t rj = 0? to +100?, v cc = +3.3v (note 1) -3.0 3.0 remote temperature error(max6658/max6659/ max6658y/max6659y) t rj = -55? to +125?, v cc = +3.3v (note 1) -5.0 +5.0 ? t a = +60? to +100?, v cc = +3.3v -2.0 +2.0 t a = 0? to +100?, v cc = +3.3v -3.0 +3.0 local temperature error(max6658/max6659) t a = -55? to +125?, v cc = +3.3v (note 2) -5.0 +5.0 ? t a = +60? to +100?, v cc = +3.3v -3.8 t a = 0? to +100?, v cc = +3.3v -4.0 local temperature error(max665_y) t a = 0? to +125?, v cc = +3.3v -4.4 ? line regulation 3.0v v cc 5.5v 0.2 0.6 m?/v supply voltage range v cc 3.0 5.5 v undervoltage lockout threshold uvlo falling edge of v cc disables adc 2.60 2.80 2.95 v undervoltage lockout hysteresis 90 mv power-on reset (por) threshold v cc , falling edge 1.5 2.0 2.5 v por threshold hysteresis 90 mv standby supply current smbus static 3 10 a operating current during conversion 0.5 1.0 ma ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
max6657/max6658/max6659 ___________________________________________________ ____________________________________ 3 note 1: t a = +25? to +85?. note 2: if both the local and the remote junction are below t a = -20?, then v cc > 3.15v. note 3: for conversion rates of 4hz or slower, the conversion time doubles. note 4: timing specifications guaranteed by design. note 5: the serial interface resets when smbclk is low for more than t timeout . note 6: a transition must internally provide at least a hold time to bridge the undefined region (300ns max) of smbclk's falling edge. electrical characteristics (continued) (v cc = +3.0v to +5.5v, t a = 0? to +125?, unless otherwise specified. typical values are at v cc = +3.3v and t a = +25?.) parameter symbol conditions min typ max units 0.25 conversions/s 40 70 average operating current 2 conversions/s 150 250 ? conversion time t conv from stop bit to conversion completed(note 4) 95 125 156 ms conversion timing error 25 % dxp and dxn leakage current in standby mode 100 na high level 80 100 120 remote-diode source current i rj low level 8 10 12 ? ( alert , overt ) v ol = 0.4v 1 output low sink current v ol = 0.6v 6 ma output high leakage current v oh = 5.5v 1 a smbus-compatible interface (smbclk, smbdata, stby ) logic input low voltage v il 0.8 v v cc = +3.0v 2.2 logic input high voltage v ih v cc = +5.5v 2.4 v input leakage current i leak v in = v gnd or v cc ? ? output low sink current i ol v ol = 0.6v 6 ma input capacitance c in 5p f smbus-compatible timing (note 4) serial-clock frequency f scl (note 5) 100 khz bus free time between stopand start condition t buf 4.7 ? start condition setup time 4.7 ? repeat start condition setuptime t su:sta 90% to 90% 50 ns start condition hold time t hd:sta 10% of smbdata to 90% of smbclk 4 s stop condition setup time t su:sto 90% of smbclk to 90% of smbdata 4 s clock low period t low 10% to 10% 4.7 ? clock high period t high 90% to 90% 4 s data setup time t hd:dat (note 6) 0 s receive scl/sda rise time t r 1 s receive scl/sda fall time t f 300 ns pulse width of spike suppressed t sp 05 0 n s smbus timeout smbdata low period for interface reset 25 37 45 ms ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
max6657/max6658/max6659 4 __________________________________________________ _____________________________________ typical operating characteristics (v cc = +3.3v, t a = +25?, unless otherwise noted.) 4.54.0 3.5 3.0 2.5 3.0 4.0 3.5 4.5 5.0 5.5 standby supply current vs. supply voltage max6657 toc01 supply voltage (v) standby supply current ( a) 0.063 0.5 1 0.125 0.25 2 4 8 16 operating supply current vs. conversion rate max6657 toc02 conversion rate (hz) operating supply current ( a) 0 200 400 600 8hz and 16hz are 1 c resolution -3 -2 -1 0 1 2 3 -55 -5 -30 20 45 70 95 120 max6659 remote temperature error vs. remote-diode temperature max6657 toc03 temperature ( c) temperature error ( c) fairchild 2n3906 -3 -2 -1 0 1 2 3 -55 -5 -30 20 45 70 95 120 local temperature error vs. die temperature max6657 toc04 temperature ( c) temperature error ( c) 10 -1-2 -3 10k 1m 100k 10m 100m temperature error vs. power-supply noise frequency max6657 toc05 frequency (hz) temperature error ( c) v in = square wave applied to v cc with no 0.1 f v cc capacitor 10 -1-2 -3 0.01k 100k 1k 10m 1g temperature error vs. common-mode noise frequency max6657 toc06 frequency (hz) temperature error ( c) v in = ac-coupled to dxn v in = 100mvp-p 10 -1-2 -3 10k 1m 100k 10m 100m temperature error vs. differential-mode noise frequency max6657 toc07 frequency (hz) temperature error ( c) v in = 10mv p-p square wave applied to dxp-dxn -5 -4 -3 -2 -1 0 04 0 5 0 20 30 10 60 70 80 90 100 temperature error vs. dxp-dxn capacitance max6657 toc08 dxp-dxn capacitance (nf) temperature error ( c) ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
max6657/max6658/max6659 ___________________________________________________ ____________________________________ 5 pin max6657max6658 max6659 name function 11v cc supply voltage input, +3v to +5.5v. bypass to gnd with a 0.1? capacitor. a 200 ? series resistor is recommended but not required for additional noise filtering. see typical operating circuit . 2 3 dxp combined remote-diode current source and a/d positive input for remote-diodechannel. do not leave dxp unconnected ; connect dxp to dxn if no remote diode is used. place a 2200pf capacitor between dxp and dxn for noise filtering. 34d x n combined remote-diode current sink and a/d negative input. dxn is internallybiased to one diode drop above ground. 46 overt1 overtemperature active-low output, open-drain. output is logic low only whentemperature is above the software programmed threshold. 5 7, 8 gnd ground 69 alert smbus alert (interrupt) active-low output, open-drain. asserts when temperatureexceeds user-set limits (high or low temperature). stays asserted until acknowledged by either reading the status register or by successfully responding to an alert response address. see alert interrupts . 7 12 smbdata smbus serial-data input/output, open-drain 8 14 smbclk smbus serial-clock input 5 add smbus address-select pin. the max6659 is set to one of three available addresses(connect to v cc , gnd, or leave open). see slave addresses section. ? 0 overt2 overtemperature active-low output, open-drain. output is logic low only whentemperature is above the software programmed threshold. ? 5 stby hardware standby input. temperature and comparison threshold data are retained instandby mode. if stby is low, the ic is put into standby mode. 2, 11, 13, 16 n.c. not internally connected. do not make connections to these pins. pin description ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
max6657/max6658/max6659 detailed description the max6657/max6658/max6659 are temperaturesensors designed to work in conjunction with a micro- processor or other intelligence in thermostatic, process-control, or monitoring applications. com- munication with the max6657/max6658/max6659 occurs through the smbus serial interface and dedicat- ed alert pins. two independent overtemperature alarms ( overt1 and overt2 ) are asserted if their software programmed temperature thresholds are exceeded.overt1 and overt2 can be connected to fans, a sys- tem shutdown, or other thermal management circuitry.the max6657/max6658/max6659 convert tempera- tures to digital data either at a programmed rate or a single conversion. conversions have a 0.125? resolu- tion (extended resolution) or 1? resolution (legacy res- olution). extended resolution represents temperature as 10 bits + sign bit and is available for autonomous con-versions that are 4hz and slower and single-shot con- versions. legacy resolution represents temperature as 7 bits + sign bit and allows for faster autonomous con- version rates of 8hz and 16hz. adc and multiplexer the averaging adc integrates over a 60ms period(each channel, typically, in the 7-bit + sign legacy mode). using an averaging adc attains excellent noise rejection. the multiplexer automatically steers bias currents through the remote and local diodes. the adc and associated circuitry measure each diode? forward volt- age and compute the temperature based on this volt- age. if the remote channel is not used, connect dxp to dxn. do not leave dxp and dxn unconnected. when a conversion is initiated, both channels are converted 6 __________________________________________________ _____________________________________ mux remotelocal adc 2 control logic smbus readwrite 8 8 address decoder 7 s r q s r q s r q diode fault dxpdxn (add) smbclk smbdata register bank command byte remote temperature local temperature alert threshold alert response address overt1 threshold (overt2 threshold) ( ) are for max6659 only max6659 only v cc max6657max6658 max6659 (stby) alert overt1 (overt2) functional diagram ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
whether they are used or not. the dxn input is biasedat one v be above ground by an internal diode to set up the adc inputs for a differential measurement.resistance in series with the remote diode causes about +1/2? error per ohm. a/d conversion sequence a conversion sequence consists of a local temperaturemeasurement and a remote temperature measurement. each time a conversion begins, whether initiated auto- matically in the free-running autoconvert mode (run/stop = 0) or by writing a ?ne-shot?command, both channels are converted, and the results of both measurements are available after the end of conver- sion. a busy status bit in the status register shows that the device is actually performing a new conversion. the results of the previous conversion sequence are still available when the adc is busy. remote-diode selection the max6657/max6658/max6659 can directly mea-sure the die temperature of cpus and other ics that have on-board temperature-sensing diodes (see typical operating circuit ) or they can measure the tem- perature of a discrete diode-connected transistor. thetype of remote diode used is set by bit 5 of the configuration byte. if bit 5 is set to zero, the remote sensor is a diode-connected transistor, and if bit 5 is set to 1, the remote sensor is a substrate or common collec-tor pnp transistor. for best accuracy, the discrete tran- sistor should be a small-signal device with its collector and base connected together. accuracy has been experimentally verified for all the devices listed in table 1. 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 at the highest expected temperature must be greater than 0.25v at 10?, and at the lowest expected tempera- ture, forward voltage must be less than 0.95v at 100?. large power transistors must not be used. also, ensure that the base resistance is less than 100 ? . tight speci- fications for forward current gain (50 < < 150, for example) indicate that the manufacturer has goodprocess controls and that the devices have consistent v be characteristics. thermal mass and self-heating when sensing local temperature, these devices areintended to measure the temperature of the pc board to which they are soldered. the leads provide a good thermal path between the pc board traces and the die. thermal conductivity between the die and the ambient air is poor by comparison, making air temperature mea- surements impractical. because the thermal mass of the pc board is far greater than that of the max6657/ max6658/max6659, the devices follow temperature changes on the pc board with little or no perceivable delay. when measuring the temperature of a cpu or other ic with an on-chip sense junction, thermal mass has virtu- ally no effect; the measured temperature of the junction tracks the actual temperature within a conversion cycle. when measuring temperature with discrete remote sen- sors, smaller packages (i.e., a sot23) yield the best thermal response times. take care to account for ther- mal 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 autoconverting at the fastest rate and simultaneously sinking maximum cur- rent at the alert output. for example, with v cc = +5.0v, a 16hz conversion rate and alert sinking 1ma, the typical power dissipation is: v cc x 450? + 0.4v x 1ma = 2.65mw j-a for the 8-pin so package is about +170?/w, so assuming no copper pc board heat sinking, the result-ing temperature rise is: ? t = 2.65mw x +170?/w = +0.45? even under these engineered circumstances, it is diffi-cult to introduce significant self-heating errors. adc noise filtering the integrating adc used has good noise rejection forlow-frequency signals such as 60hz/120hz power-sup- ply hum. in noisy environments, high-frequency noise reduction is needed for high-accuracy remote mea- max6657/max6658/max6659 ___________________________________________________ ____________________________________ 7 manufacturer model number central semiconductor (usa) cmpt3904 fairchild semiconductor (usa) 2n3904, 2n3906 on semiconductor (usa) 2n3904, 2n3906 rohm semiconductor (usa) sst3904 samsung (korea) kst3904-tf siemens (germany) smbt3904 zetex (england) fmmt3904ct-nd note: transistors must be diode connected (base shorted to collector). table 1. remote-sensor transistor ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
max6657/max6658/max6659 surements. the noise can be reduced with careful pcboard layout and proper external noise filtering. high-frequency emi is best filtered at dxp and dxn with an external 2200pf capacitor. larger capacitor values can be used for added filtering, but do not exceed 3300pf because it can introduce errors due to the rise time of the switched current source. pc board layout follow these guidelines to reduce the measurementerror of the temperature sensors: 1) place the max6657/max6658/max6659 as close as is practical to the remote diode. in noisy environ-ments, such as a computer motherboard, this dis- tance can be 4in to 8in (typ). this length can be increased if the worst noise sources are avoided. noise sources include crts, clock generators, memory buses, and isa/pci buses. 2) do not route the dxp-dxn lines next to the deflec- tion coils of a crt. also, do not route the tracesacross fast digital signals, which can easily intro- duce +30? error, even with good filtering. 3) route the dxp and dxn traces in parallel and in close proximity to each other, away from any highervoltage traces, such as +12vdc. leakage currents from pc board contamination must be dealt with carefully since a 20m ? leakage path from dxp to ground causes about +1? error. if high-voltagetraces are unavoidable, connect guard traces to gnd on either side of the dxp-dxn traces (figure 1). 4) route through as few vias and crossunders as pos- sible to minimize copper/solder thermocoupleeffects. 5) when introducing a thermocouple, make sure that both the dxp and the dxn paths have matchingthermocouples. a copper-solder thermocouple exhibits 3?/?, and it takes about 200? of voltage error at dxp-dxn to cause a +1? measurement error. adding a few thermocouples causes a negli- gible error. 6) use wide traces. narrow traces are more inductive and tend to pick up radiated noise. the 10mil widthsand spacings that are recommended in figure 1 are not absolutely necessary, as they offer only a minor improvement in leakage and noise over narrow traces. use wider traces when practical. 7) add a 200 ? resistor in series with v cc for best noise filtering (see typical operating circuit ). twisted-pair and shielded cables use a twisted-pair cable to connect the remote sensorfor remote-sensor distances longer than 8in or in very noisy environments. twisted-pair cable lengths can be between 6ft and 12ft before noise introduces excessive errors. for longer distances, the best solution is a shielded twisted pair like that used for audio micro- phones. for example, belden #8451 works well for dis- tances up to 100ft in a noisy environment. at the device, connect the twisted pair to dxp and dxn and the shield to gnd. leave the shield unconnected at the remote sensor. 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. for every 1 ? of series resistance, the error is approxi- mately +1/2?. low-power standby mode standby mode reduces the supply current to less than10? by disabling the adc. enter hardware standby (max6659 only) by forcing the stby pin low, or enter software standby by setting the run/stop bit to 1 inthe configuration byte register. hardware and software standbys are very similar?ll data is retained in memo- ry, and the smb interface is alive and listening for smbus commands. the only difference is that in soft- ware standby mode, the one-shot command initiates a conversion. with hardware standby, the one-shot com- mand is ignored. activity on the smbus causes the device to draw extra supply current. driving the stby pin low overrides any software con- version command. if a hardware or software standbycommand is received while a conversion is in progress, the conversion cycle is interrupted, and the tempera- 8 __________________________________________________ _____________________________________ minimum 10mils10mils 10mils 10mils gnd dxn dxp gnd figure 1. recommended dxp-dxn pc traces ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
ture registers are not updated. the previous data is notchanged and remains available. smbus digital interface from a software perspective, each of the max6657/ max6658/max6659 appears as a series of 8-bit regis- ters that contain temperature data, alarm threshold values, and control bits. a standard smbus-compatible 2-wire serial interface is used to read temperature data and write control bits and alarm threshold data. the device responds to the same smbus slave address for access to all functions. the max6657/max6658/max6659 employ four stan- dard smbus protocols: write byte, read byte, send byte, and receive byte (figures 2, 3, and 4). the short- er receive byte protocol allows quicker transfers, pro- vided that the correct data register was previously selected by a read byte instruction. use caution with the shorter protocols in multimaster systems, since a second master could overwrite the command byte with- out informing the first master. when the conversion rate is greater than 4hz, temperature data can be read from the read internal temperature (00h) and read external temperature (01h) registers. the temperature data format is 7 bits + sign in two's-complement form for each channel, with the lsb repre- senting 1? (table 2). the msb is transmitted first. when the conversion rate is 4hz or less, the first 8 bits of temperature data can be read from the read internal temperature (00h) and read external temperature (01h) registers, the same as for faster conversion rates. an additional 3 bits can be read from the read external extended temperature (10h) and read internal extended temperature (11h) registers, which extends the data to 10 bits + sign and the resolution to +0.125? per lsb (table 3). when a conversion is complete, the main register and the extended register are updated almost simultane- ously. ensure that no conversions are completed between reading the main and extended registers so that when data that is read, both registers contain the result of the same conversion. to ensure valid extended data, read extended resolu- tion temperature data using one of the following approaches: 1) put the max6657/max6658/max6659 into standby mode by setting bit 6 of the configuration register to max6657/max6658/max6659 ___________________________________________________ ___________________________________ 9 figure 2. smbus protocols 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 whichregister you are writing to data byte: data goes into the registerset 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 command slave address: equiva-lent to chip-select line command byte: selectswhich register you are reading from slave address: repeateddue to change in data- flow direction data byte: reads fromthe register set by the command byte ack 7 bits address wr 8 bits command ack p 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 fromthe 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 ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
max6657/max6658/max6659 1. initiate a one-shot conversion using commandbyte 0fh. when this conversion is complete, read the contents of the temperature data registers. 2) if the max6657/max6658/max6659 are in run mode, read the status register. if a conversion is inprogress, the busy bit is set to 1. wait for the con- version to complete as indicated by the busy bit being set to 0, then read the temperature data reg- isters. note that the power-on reset sets the conver- sion rate to 16hz, so no extended data is valid without reducing the conversion rate to 4hz or less. diode fault alarm there is a continuity fault detector at dxp that detectsan open circuit between dxp and dxn, or a dxp short to v cc , gnd, or dxn. if an open or short circuit exists, the external temperature register is loaded with 10000000. additionally, if the fault is an open circuit, bit 2 (open) of the status byte is set to 1 and the alert con- dition is activated at the end of the conversion. immediately after por, the status register indicates that no fault is present until the end of the first conversion. 10 _________________________________________________ _____________________________________ 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 l m a = start conditionb = 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 f = acknowledge bit clocked into masterg = msb of data clocked into master h = lsb of data clocked into master i = master pulls data line low j = acknowledge clocked into slavek = acknowledge clock pulse l = stop condition m = new start condition figure 4. smbus read 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 conditionb = 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 masterg = msb of data clocked into slave h = lsb of data clocked into slave i = master pulls data line low j = acknowledge clocked into slavek = acknowledge clock pulse l = stop condition m = new start condition figure 3. smbus write timing diagram ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
alarm threshold registers four registers store alert threshold values?ne high- temperature (t high ) and one low-temperature (t low ) register each for the local and remote channels. ifeither measured temperature equals or exceeds the corresponding alert threshold value, the alert out- put is asserted. the por state of both alert t high registers is 0100 0110 or +70? and the por state of t low registers is 1100 1001 or -55?.four additional registers store remote and local alarm threshold data corresponding to the overt1 and overt2 (max6659 only) outputs. the values stored in these registers are high-temperature thresholds. if anyone of the measured temperatures equals or exceeds the corresponding alarm threshold value, an overt output is asserted. the por state of the overt thresh- old is 0101 0101 or +85?. alert interrupts an alert interrupt occurs when the internal or external temperature reading exceeds a high or low tempera-ture limit (user programmed) or when the remote diode is disconnected (for continuity fault detection). the alert interrupt output signal is latched and can be cleared only by either reading the status register or bysuccessfully responding to an alert response address. in both cases, the alert is cleared even if the fault con- dition still exists, but is reasserted at the end of the next conversion. the interrupt does not halt automatic con- versions. the interrupt output pin is open-drain so that multiple devices can share a common interrupt line. the interrupt rate never exceeds the conversion rate. alert response address the smbus alert response interrupt pointer providesquick 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 (0001100). then, any slave device that generated an interrupt attempts to identify itself by putting its own address on the bus (table 8). 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 cleared. (the conditions for clearing an alert vary,depending on the type of slave device.) successful completion of the alert response protocol clears the interrupt latch, provided the condition that caused the alert no longer exists. if the condition still exists, the device reasserts the alert interrupt at the end of the next conversion. overt overtemperature alarm/warning outputs overt1 and overt2 (max6659 only) are asserted when the temperature rises to a value programmed inthe appropriate threshold register. they are deasserted when the temperature drops below this threshold minus the hysteresis. an overt output can be used to acti- vate a cooling fan, send a warning, or trigger a system shutdown to prevent component damage. the hyst byte sets the amount of hysteresis for both overt out- puts. the data format for the hyst byte is the same for the other temperature registers (table 2). max6657/max6658/max6659 ___________________________________________________ ___________________________________ 11 fractional temperature contents of extended register 0.000 000x xxxx 0.125 001x xxxx 0.250 010x xxxx 0.375 011x xxxx 0.500 100x xxxx 0.625 101x xxxx 0.750 110x xxxx 0.875 111x xxxx table 3. extended resolution register note: extended resolution applies only for conversion rates of 4hz and slower. digital output temp ( c) max6657 max6658max6659 130.00 0 111 1111 0 111 1111 127.00 0 111 1111 0 111 1111 126.00 0 111 1111 0 111 1111 25 0 001 1001 0 001 1001 0.00 0 000 0000 0 000 0000 -1 1 000 0000 1 111 1111 -25 1 000 0000 1 110 0111 -55 1 000 0000 1 100 1001 diode fault (short or open) 1 000 0000 1 000 0000 table 2. data format (two's complement) ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
max6657/max6658/max6659 for example, overt1 has a threshold set to +50? and is connected to a fan. overt2 has a threshold of +75? and is connected to a system shutdown. if thesystem reaches +50?, the fan turns on, trying to cool the system. if the system continues to heat up to the critical temperature of +75?, overt2 causes the sys- tem to shut down. command byte functions the 8-bit command byte register (table 4) is the masterindex that points to the various other registers within the max6657/max6658/max6659. this register? por state is 0000 0000, so a receive byte transmission (a protocol that lacks the command byte) occurring immediately after por returns the current local temperature data. one-shot the one-shot command immediately forces a new con-version cycle to begin. if the one-shot command is received when the max6657/max6658/max6659 are in software standby mode ( run /stop bit = 1), a new conversion is begun, after which the device returns tostandby 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 autocon- vert mode ( run /stop bit = 0) between conversions, a new conversion begins, the conversion rate timer isreset, and the next automatic conversion takes place after a full delay elapses. configuration byte functions the configuration byte register (table 5) is a read-writeregister with several functions. bit 7 is used to mask (dis- able) interrupts. bit 6 puts the device into software stand- by mode (stop) or autonomous (run) mode. bit 5 selects the type of external junction (set to 1 for a sub- strate pnp on an ic or set to 0 for a discrete diode-con- nected transistor) for optimized measurements. bits 0 to 4 are reserved and return a zero when read. 12 _________________________________________________ _____________________________________ register address por state function rlts 00h 0000 0000 read internal temperature rrte 01h 0000 0000 read external temperature rsl 02h 1000 0000 read status register rcl 03h 0010 0000 read configuration byte rcra 04h 0000 1000 read conversion rate byte rlhn 05h 0100 0110 read internal high limit rlli 06h 1100 1001 read internal low limit rrhi 07h 0100 0110 read external high limit rrls 08h 1100 1001 read external low limit wca 09h 0010 0000 write configuration byte wcrw 0ah 0000 1000 write conversion rate byte wlho 0bh 0100 0110 write internal high limit wllm 0ch 1100 1001 write internal low limit wrha 0dh 0100 0110 write external high limit wrln 0eh 1100 1001 write external low limit osht 0fh n/a one shot reet 10h 0000 0000 read external extended temperature riet 11h 0000 0000 read internal extended temperature rwo2e 16h 0101 0101 read/write external overt2 limit (max6659 only) rw02i 17h 0101 0101 read/write internal overt2 limit (max6659 only) rwoe 19h 0101 0101 read/write external overt1 limit rwoi 20h 0101 0101 read/write internal overt1 limit hyst 21h 0000 1010 overtemperature hysteresis feh 4dh read manufacture id table 4. command byte register assignments ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
max6657/max6658/max6659 ___________________________________________________ ___________________________________ 13 status byte functions the status byte (table 6) indicates which (if any) tem-perature thresholds have been exceeded. this byte also indicates whether the adc is converting and if there is an open-circuit fault detected with the external sense junction. after por, the normal state of the msb is 1 and all the other flag bits are 0, assuming no alert or overtemperature conditions are present. bits 2 through 6 of the status register are cleared by any successful read of the status register, unless the fault persists. the alert output follows the status flag bit. both arecleared when successfully read, but if the condition still exists, they reassert at the end of the next conversion. the bits indicating overt1 (bits 0 and 1) are cleared only when the condition no longer exists. reading the status byte does not clear the overt1 outputs or fault bits. one way to eliminate the fault condition is for themeasured temperature to drop below the temperature threshold minus the hysteresis value. another way to eliminate the fault condition is by writing new values for the overt1 threshold or hysteresis so that a fault con- dition is no longer present. note that the status byte does not provide status of overt2 . the max6657/max6658/max6659 incorporate collisionavoidance so that completely asynchronous operation is allowed between smbus operations and temperature conversions. when autoconverting, 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. in these circum- stances, it is best not to rely on the status bits to indi- cate reversals in long-term temperature changes. instead, use a current temperature reading to establish the trend direction. conversion rate byte the conversion rate register (table 7) programs thetime interval between conversions in free-running autonomous mode ( run /stop = 0). this variable rate bit name por state function 7 (msb) mask1 0 masks alert interrupts if a 1. 6 run /stop 0 standby mode control bit; if a 1, standby mode is initiated. 5 spnp 1 set to 1 when the remotesensor is a substrate or common collector pnp. set to 0 when the remote sensor is a diode-connected discrete transistor. 4 to 0 rfu 0 reserved table 5. configuration-byte bit assignments bit name por state function 7 (msb) busy 1 a/d is busy converting when high. 6 lhigh 0 internal high-temperature alarm has tripped when high; cleared by por or readout ofthe status register if the fault condition no longer exists. 5 llow 0 internal low-temperature alarm has tripped when high; cleared by por or readout ofthe status register if the fault condition no longer exists. 4 rhigh 0 external high-temperature alarm has tripped when high; cleared by por or readout ofthe status register if the fault condition no longer exists. 3 rlow 0 external low-temperature alarm has tripped when high; cleared by por or readout ofthe status register if the fault condition no longer exists. 2 open 0 a high indicates an external diode open; cleared by por or readout of the statusregister if the fault condition no longer exists. 1 eot1 0 a high indicates the external junction temperature exceeds the external overt1threshold. 0 iot1 0 a high indicates the internal junction temperature exceeds the internal overt1threshold. table 6. status register bit assignments ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
max6657/max6658/max6659 control can be used to reduce the supply current inportable-equipment applications. the conversion rate byte? por state is 08h (16hz). the max6657/ max6658/max6659 use only the 4 least-significant bits (lsbs) of this register. the 4 most-significant bits (msbs) are ?on? care?and should be set to zero when possible. the conversion rate tolerance is ?5% at any rate setting. valid a/d conversion results for both channels are available one total conversion time (125ms nominal, 156ms maximum) after initiating a conversion, whether conversion is initiated through the run /stop bit, hard- ware stby pin, one-shot command, or initial power-up. slave addresses the max6657/max6658 have a fixed address of1001100. the max6659 can be programmed to have one of three different addresses, allowing up to three devices to reside on the same bus without address conflicts. table 8 lists address information. the address pin state is checked at por only, and the address data stays latched to reduce quiescent supply current due to the bias current needed for high-z state detection. the max6657/max6658/max6659 also respond to the smbus alert response slave address (see alert response address section). por and uvlo the max6657/max6658/max6659 have a volatilememory. to prevent unreliable power-supply conditions from corrupting the data in memory and causing erraticbehavior, a por voltage detector monitors v cc and clears the memory if v cc falls below 1.7v (typ, see electrical characteristics ). when power is first applied and v cc rises above 2.0v (typ), the logic blocks begin operating, although reads and writes at v cc levels below 3.0v are not recommended. a second v cc com- parator and the adc undervoltage lockout (uvlo)comparator prevent the adc from converting until there is sufficient headroom (v cc = +2.8v typ). power-up defaults power-up defaults include: adc begins autoconverting at a 16hz rate (legacy resolution). thigh and tlow registers are set to default limits, respectively. interrupt latch is cleared. address-select pin is sampled (max6659 only). command register is set to 00h to facilitate quick internal receive byte queries. hysteresis is set to 10?. transistor type is set to a substrate or common col- lector pnp. 14 _________________________________________________ _____________________________________ data conversion rate (hz) 00h 0.0625 01h 0.125 02h 0.25 03h 0.5 04h 1 05h 2 06h 4 07h 8 08h 16 09h 16 0ah-ffh reserved add connection address gnd 1001100 v cc 1001110 unconnected 1001101 table 8. slave address decoding for max6659 note: extended resolution applies only for conversion rates of 4hz or slower. table 7. conversion-rate control byte bit name function 7 (msb) add7 6 add6 5 add5 4 add4 3 add3 2 add2 1 add1 provide the currentmax6659 slave address that was latched at por (table 8) 0 (lsb) 1 logic 1 table 9. read format for alert response address (000 1100) ??, smbus-compatible remote/local temperature sensors with overtemperature alarms downloaded from: http:///
max6657/max6658/max6659 ___________________________________________________ ___________________________________ 15 chip information process: bicmos v cc smbdata smbclk data clock interrupted to p to fan driver () are max6659 only to system shutdown (add) gnd p 3.3v 200 ? 2200pf 10k ? each 0.1 f dxpdxn alert overt1 (overt2) (stby) max6657max6658 max6659 typical operating circuit ??, smbus-compatible remote/local temperature sensors with overtemperature alarms package information for the latest package outline information and land patterns, goto www.maxim-ic.com/packages . note that a ?? ?? or ??in the package code indicates rohs status only. package draw-ings 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. 8 so s8-5 21-0041 90-0096 16 qsop e16-5 21-0055 90-0167 ordering information (continued) part measured temp range pin-package max6658 msa -55? to +125? 8 so max6658msa+ -55? to +125? 8 so max6658msa-t -55? to +125? 8 so max6658msa+t -55? to +125? 8 so max6659 mee -55? to +125? 16 qsop max6659mee+ -55? to +125? 16 qsop max6659mee-t -55? to +125? 16 qsop max6659mee+t -55? to +125? 16 qsop note: all devices are specified over the -55? to +125? oper- ating temperature range. + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. downloaded from: http:///
max6657/max6658/max6659 1? remote/local temperature sensors with smbus serial interface and overtemperature alarms maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 16 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2010 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. revision history revision number revision date description pages changed 5 10/10 updated the ordering information table to include lead(pb)-free parts, added the soldering temperature to the absolute maximum ratings section, replaced the package outline drawings with the package information table 1, 2, 15 downloaded from: http:///

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