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general description the max6689 precision multichannel temperature sen- sor monitors its own temperature and the temperatures of up to six external diode-connected transistors. all temperature channels have programmable alert thresh- olds. channels 1, 4, 5, and 6 also have programmable overtemperature thresholds. when the measured tem- perature of a channel exceeds the respective thresh- old, a status bit is set in one of the status registers. two open-drain outputs, overt and alert , assert corre- sponding to these bits in the status register. the 2-wire serial interface supports the standard system management bus (smbus) protocols: write byte, read byte, send byte, and receive byte for reading the tem- perature data and programming the alarm thresholds. the max6689 is specified for an operating temperature range of -40? to +125? and is available in 20-pin qsop and tssop packages. applications desktop computers notebook computers workstations servers features ? six thermal-diode inputs ? local temperature sensor ? 1? remote temperature accuracy (+60? to +100?) ? temperature monitoring begins at por for fail- safe system protection ? alert and overt outputs for interrupts, throttling, and shutdown ? stby input for hardware standby mode ? small, 20-pin qsop and tssop packages ? 2-wire smbus interface max6689 7-channel precision temperature monitor ________________________________________________________________ maxim integrated products 1 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. ordering information 20 19 18 17 16 15 14 13 1 2 3 4 5 6 7 8 gnd smbclk smbdata dxn2 dxp2 dxn1 dxp1 v cc n.c. dxn4 dxp4 dxn3 dxp3 12 11 9 10 dxp6 dxn6 dxn5 dxp5 max6689 alert overt stby 2200pf 2200pf 2200pf 2200pf 2200pf cpu 2200pf gpu 0.1 f to system shutdown interrupt to p data clk 4.7k each +3.3v typical application circuit 19-0567; rev 1; 8/07 part pin- package slave address pkg code max6689ep34+ 20 qsop 0011 010 e20-1 max6689ep38+ 20 qsop 0011 100 e20-1 max6689ep9a+ 20 qsop 1001 101 e20-1 max6689ep9e+ 20 qsop 1001 111 e20-1 max6689up34+ 20 tssop 0011 010 u20-2 max6689up38+ 20 tssop 0011 100 u20-2 max6689up9a+ 20 tssop 1001 101 u20-2 max6689up9e+ 20 tssop 1001 111 u20-2 smbus is a trademark of intel corp. note: all devices are specified over the -40? to +125? temperature range. + denotes lead-free package. pin configuration appears at end of data sheet.
max6689 7-channel precision temperature monitor 2 _______________________________________________________________________________________ absolute maximum ratings 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 , sck, sda, alert , overt , stby to gnd .....-0.3v to +6v dxp_ to gnd..............................................-0.3v to (v cc + 0.3v) dxn_ to gnd ........................................................-0.3v to +0.8v sda, alert , overt current .............................-1ma to +50ma dxn current .......................................................................?ma continuous power dissipation (t a = +70?) 20-pin qsop (derate 9.1mw/? above +70?) ..................................727.3mw 20-pin tssop (derate 11.0mw/? above +70?) ..............................879.1mw esd protection (all pins, human body model) ................?000v operating temperature range .........................-40? to +125? junction temperature ......................................................+150? storage temperature range .............................-60? to +150? lead temperature (soldering, 10s) .................................+300? electrical characteristics (v cc = +3.0v to +5.5v, v stby = v cc , t a = -40? to +125?, unless otherwise noted. typical values are at v cc = +3.3v and t a = +25?.) (note 1) parameter symbol conditions min typ max units supply voltage v cc 3.0 5.5 v software standby supply current i ss smbus static 30 ? operating current i cc during conversion 500 1000 ? channel 1 only 11 temperature resolution other diode channels 8 bits t a = t rj = +60? to +100? -1.0 +1.0 t a = t rj = 0? to +125? -3.0 +3.0 remote temperature accuracy v cc = 3.3v dxn_ grounded, t rj = t a = 0? to +85? ?.5 o c t a = +60? to +100? -3.3 +0.7 local temperature accuracy v cc = 3.3v t a = 0? to +125? -5.0 +1.0 o c supply sensitivity of temperature accuracy 0.2 o c/v resistance cancellation off 95 125 156 remote channel 1 conversion time t conv1 resistance cancellation on 190 250 312 ms remote channels 2 through 6 conversion time t conv_ 95 125 156 ms high level 80 100 120 remote-diode source current i rj low level 8 10 12 ? undervoltage-lockout threshold uvlo falling edge of v cc disables adc 2.30 2.80 2.95 v undervoltage-lockout hysteresis 90 mv power-on reset (por) threshold v cc falling edge 1.2 2.0 2.5 v por threshold hysteresis 90 mv alert , overt i sink = 1ma 0.3 output low voltage v ol i sink = 6ma 0.5 v output leakage current 1a
max6689 7-channel precision temperature monitor _______________________________________________________________________________________ 3 electrical characteristics (continued) (v cc = +3.0v to +5.5v, v stby = v cc , t a = -40? to +125?, unless otherwise noted. typical values are at v cc = +3.3v and t a = +25?.) (note 1) parameter symbol conditions min typ max units smbus interface (scl, sda), stby logic-input low voltage v il 0.8 v v cc = 3.0v 2.2 logic-input high voltage v ih v cc = 5.0v 2.4 v input leakage current -1 +1 ? output low voltage v ol i sink = 6ma 0.3 v input capacitance c in 5pf smbus-compatible timing (figures 3 and 4) (note 2) serial-clock frequency f scl (note 3) 400 khz f scl = 100khz 4.7 bus free time between stop and start condition t buf f scl = 400khz 1.6 ? f scl = 100khz 4.7 start condition setup time f scl = 400khz 0.6 ? 90% of scl to 90% of sda, f scl = 100khz 0.6 repeat start condition setup time t su:sta 90% of scl to 90% of sda, f scl = 400khz 0.6 ? start condition hold time t hd:sta 10% of sda to 90% of scl 0.6 ? 90% of scl to 90% of sda, f scl = 100khz 4 stop condition setup time t su:sto 90% of scl to 90% of sda, f scl = 400khz 0.6 ? 10% to 10%, f scl = 100khz 1.3 clock-low period t low 10% to 10%, f scl = 400khz 1.3 ? clock-high period t high 90% to 90% 0.6 ? f scl = 100khz 300 data hold time t hd:dat f scl = 400khz (note 4) 900 ns f scl = 100khz 250 data setup time t su:dat f scl = 400khz 100 ns f scl = 100khz 1 receive scl/sda rise time t r f scl = 400khz 0.3 ? receive scl/sda fall time t f 300 ns pulse width of spike suppressed t sp 050ns smbus timeout t timeout sda low period for interface reset 25 37 45 ms note 1: all parameters are tested at t a = +85?. specifications over temperature are guaranteed by design. note 2: timing specifications are guaranteed by design. note 3: the serial interface resets when scl is low for more than t timeout . note 4: a transition must internally provide at least a hold time to bridge the undefined region (300ns max) of scl? falling edge.
max6689 7-channel precision temperature monitor 4 _______________________________________________________________________________________ typical operating characteristics (v cc = 3.3v, v stby = v cc , t a = +25?, unless otherwise noted.) software standby supply current vs. supply voltage max6689 toc01 supply voltage (v) standby supply current ( a) 5.3 4.8 4.3 3.8 1 2 3 4 5 6 7 8 9 10 11 12 0 3.3 supply current vs. supply voltage max6689 toc02 supply voltage (v) supply current ( a) 5.3 4.8 3.8 4.3 325 330 335 340 350 345 355 360 320 3.3 -4 -2 -3 0 -1 2 1 3 050 25 75 100 125 remote temperature error vs. remote-diode temperature max6689 toc03 remote-diode temperature ( c) temperature error ( c) -4 -3 -2 -1 0 1 2 3 4 0 25 50 75 100 125 local temperature error vs. die temperature max6689 toc04 die temperature ( c) temperature error ( c) remote-diode temperature error vs. power-supply noise frequency max6689 toc05 frequency (mhz) temperature error ( c) -4 -3 -2 -1 0 1 2 3 4 5 -5 0.1 1 100mv p-p local temperature error vs. power-supply noise frequency max6689 toc06 frequency (mhz) temperature error ( c) 0.1 0.01 -4 -3 -2 -1 0 1 2 3 4 5 -5 0.001 1 100mv p-p remote temperature error vs. common-mode noise frequency max6689 toc07 frequency (mhz) temperature error ( c) 1 0.1 0.01 -4 -3 -2 -1 0 1 2 3 4 5 -5 0.001 10 100mv p-p
max6689 7-channel precision temperature monitor _______________________________________________________________________________________ 5 remote temperature error vs. common-mode noise frequency max6689 toc08 frequency (mhz) temperature error ( c) 1 0.1 0.01 -4 -3 -2 -1 0 1 2 3 4 5 -5 0.001 10 100mv p-p typical operating characteristics (continued) (v cc = 3.3v, v stby = v cc , t a = +25?, unless otherwise noted.) temperature error vs. dxp-dxn capacitance max6689 toc09 dxp-dxn capacitance (nf) temperature error ( c) 10 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0 -5.0 1100 pin description pin name function 1 dxp1 combined current source and a/d positive input for channel 1 remote diode. connect to the anode of a remote-diode-connected temperature-sensing transistor. leave floating or connect to v cc if no remote diode is used. place a 2200pf capacitor between dxp1 and dxn1 for noise filtering. 2 dxn1 cathode input for channel 1 remote diode. connect the cathode of the channel 1 remote-diode- connected transistor to dxn1. 3 dxp2 combined current source and a/d positive input for channel 2 remote diode. connect to the anode of a remote-diode-connected temperature-sensing transistor. leave floating or connect to v cc if no remote diode is used. place a 2200pf capacitor between dxp2 and dxn2 for noise filtering. 4 dxn2 cathode input for channel 2 remote diode. connect the cathode of the channel 2 remote-diode- connected transistor to dxn2. 5 dxp3 combined current source and a/d positive input for channel 3 remote diode. connect to the anode of a remote-diode-connected temperature-sensing transistor. leave floating or connect to v cc if no remote diode is used. place a 2200pf capacitor between dxp3 and dxn3 for noise filtering. 6 dxn3 cathode input for channel 3 remote diode. connect the cathode of the channel 1 remote-diode- connected transistor to dxn3. 7 dxp4 combined current source and a/d positive input for channel 4 remote diode. connect to the anode of a remote-diode-connected temperature-sensing transistor. leave floating or connect to v cc if no remote diode is used. place a 2200pf capacitor between dxp4 and dxn4 for noise filtering. 8 dxn4 cathode input for channel 4 remote diode. connect the cathode of the channel 1 remote-diode- connected transistor to dxn4.
max6689 detailed description the max6689 is a precision multichannel temperature monitor that features one local and six remote tempera- ture-sensing channels with a programmable alert threshold for each temperature channel and a program- mable overtemperature threshold for channels 1, 4, 5, and 6 (see figure 1). communication with the max6689 is achieved through the smbus serial interface and a dedicated alert pin. the alarm outputs, overt and alert , assert if the software-programmed temperature thresholds are exceeded. alert typically serves as an interrupt, while overt can be connected to a fan, sys- tem shutdown, or other thermal-management circuitry. adc conversion sequence in the default conversion mode, the max6689 starts the conversion sequence by measuring the temperature on channel 1, followed by 2, 3, local channel, 4, 5, and 6. the conversion result for each active channel is stored in the corresponding temperature data register. in some systems, one of the remote thermal diodes may be monitoring a location that experiences temperature changes that occur much more rapidly than in the other channels. if faster temperature changes must be moni- tored in one of the temperature channels, the max6689 allows channel 1 to be monitored at a faster rate than the other channels. in this mode (set by writing a 1 to bit 4 of the configuration 1 register), measurements of channel 1 alternate with measurements of the other channels. the sequence becomes channel 1, channel 2, channel 1, channel 3, channel 1, etc. note that the time required to measure all seven channels is consid- erably greater in this mode than in the default mode. low-power standby mode enter software standby mode by setting the stop bit to 1 in the configuration 1 register. enter hardware standby by pulling stby low. software standby mode disables the adc and reduces the supply current to approxi- mately 30?. hardware standby mode halts the adc clock, but the supply current is approximately 350?. during either software or hardware standby, data is retained in memory. during hardware standby, the smbus interface is inactive. during software standby, the smbus interface is active and listening for commands. the timeout is enabled if a start condition is recognized on smbus. activity on the smbus causes the supply cur- rent to increase. if a standby command is received while a conversion is in progress, the conversion cycle is inter- 7-channel precision temperature monitor 6 _______________________________________________________________________________________ pin name function 9 dxp5 combined current source and a/d positive input for channel 5 remote diode. connect to the anode of a remote-diode-connected temperature-sensing transistor. leave floating or connect to v cc if no remote diode is used. place a 2200pf capacitor between dxp5 and dxn5 for noise filtering. 10 dxn5 cathode input for channel 5 remote diode. connect the cathode of the channel 1 remote-diode- connected transistor to dxn5. 11 dxn6 cathode input for channel 6 remote diode. connect the cathode of the channel 1 remote-diode- connected transistor to dxn6. 12 dxp6 combined current source and a/d positive input for channel 6 remote diode. connect to the anode of a remote-diode-connected temperature-sensing transistor. leave floating or connect to v cc if no remote diode is used. place a 2200pf capacitor between dxp6 and dxn6 for noise filtering. 13 stby active-low standby input. drive stby logic-low to place the max6689 in standby mode, or logic-high for operate mode. temperature and threshold data are retained in standby mode. 14 n.c. no connection. must be connected to ground. 15 overt overtemperature active-low, open-drain output. overt asserts low when the temperature of channels 1, 4, 5, and 6 exceeds the programmed threshold limit. 16 v cc supply voltage input. bypass to gnd with a 0.1? capacitor. 17 alert smbus alert (interrupt), active-low, open-drain output. alert asserts low when the temperature of any channel exceeds the programmed alert threshold. 18 smbdata smbus serial-data input/output. connect to a pullup resistor. 19 smbclk smbus serial-clock input. connect to a pullup resistor. 20 gnd ground pin description (continued)
rupted, and the temperature registers are not updated. the previous data is not changed and remains available. smbus digital interface from a software perspective, the max6689 appears as a series of 8-bit registers that contain temperature mea- surement 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 same smbus slave address also provides access to all functions. the max6689 employs four standard smbus protocols: write byte, read byte, send byte, and receive byte (figure 2). the shorter receive byte protocol allows quicker transfers, provided that the correct data regis- ter 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 without informing the first master. figure 3 is the smbus write-timing diagram and figure 4 is the smbus read-timing diagram. the remote diode 1 measurement channel provides 11 bits of data (1 lsb = 0.125?). all other temperature- measurement channels provide 8 bits of temperature data (1 lsb = 1?). the 8 most significant bits (msbs) can be read from the local temperature and remote temperature registers. the remaining 3 bits for remote diode 1 can be read from the extended temperature max6689 7-channel precision temperature monitor _______________________________________________________________________________________ 7 figure 1. internal block diagram dxp1 dxn1 dxp2 dxn2 dxp3 dxn3 dxp4 dxn4 dxp5 dxn5 dxp6 dxn6 input buffer 10/100 a v cc ref count counter command byte remote temperatures local temperatures register bank alert threshold overt threshold alert response address alarm alu adc smbus interface max6689 scl sda overt avert stby
max6689 register. if extended resolution is desired, the extended resolution register should be read first. this prevents the most significant bits from being overwritten by new conversion results until they have been read. if the most significant bits have not been read within an smbus timeout period (nominally 37ms), normal updat- ing continues. table 1 shows the main temperature register (high-byte) data format, and table 2 shows the extended resolution register (low-byte) data format. diode fault detection if a channel? input dxp_ and dxn_ are left open, the max6689 detects a diode fault. an open diode fault does not cause either alert or overt to assert. a bit in the status register for the corresponding channel is set to 1 and the temperature data for the channel is stored as all 1s (ffh). it takes approximately 4ms for the max6689 to detect a diode fault. once a diode fault is detected, the max6689 goes to the next channel in the conversion sequence. depending on operating conditions, a shorted diode may or may not cause alert or overt to assert, so if a channel will not be used, disconnect its dxp and dxn inputs. 7-channel precision temperature monitor 8 _______________________________________________________________________________________ figure 2. smbus protocols temp (c) digital output > +127 0111 1111 +127 0111 1111 +126 0111 1110 +25 0001 1001 0 0000 0000 < 0 0000 0000 diode fault (open) 1111 1111 diode fault (short) 1111 1111 or 1110 1110 table 1. main temperature register (high-byte) data format temp (c) digital output 0 000x xxxx +0.125 001x xxxx +0.250 010x xxxx +0.375 011x xxxx +0.500 100x xxxx +0.625 101x xxxx +0.725 110x xxxx table 2. extended resolution temperature register (low-byte) data format s address wr ack ack p data ack command 7 bits 1 8 bits 8 bits slave address: equiva- lent to chip-select line of a 3-wire interface data byte: data goes into the register set by the command byte (to set thresholds, configuration masks, and sampling rate) write byte format s address address wr ack ack p s rd ack /// data command 7 bits 7 bits 8 bits 8 bits read byte format slave address: equiva- lent to chip select line command byte: selects which register you are reding from sp address wr ack ack command 7 bits 8 bits send byte format command byte: sends com- mand with no data, usually used for one-shot command sp address rd ack /// data 7 bits 8 bits receive byte format 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 slave address: repeated due to change in data- flow direction data byte: reads from the register set by the command byte s = start condition. p = stop condition. shaded = slave transmission. /// = not acknowledged.
alarm threshold registers there are 11 alarm threshold registers that store over- temperature alert and overt threshold values. seven of these registers are dedicated to store one local alert temperature threshold limit and six remote alert temperature threshold limits (see the alert interrupt mode section). the remaining four registers are dedicated to remote channels 1, 4, 5, and 6 to store overtemperature threshold limits (see the overt overtemperature alarms section). access to these reg- isters is provided through the smbus interface. alert interrupt mode an alert interrupt occurs when the internal or external temperature reading exceeds a high-temperature limit (user programmable). the alert interrupt output sig- nal can be cleared by reading the status register(s) associated with the fault(s) or by successfully respond- ing to an alert response address transmission by the master. in both cases, the alert is cleared but is reasserted at the end of the next conversion if the fault condition still exists. the interrupt does not halt automat- ic conversions. the alert output is open drain so that multiple devices can share a common interrupt line. all alert interrupts can be masked using the configuration 3 register. the por state of these registers is shown in table 1. max6689 7-channel precision temperature monitor _______________________________________________________________________________________ 9 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 hij smbdata t su:sta t hd:sta t low t high t su:dat t su:sto t buf lm k e = slave pulls smbdata line low. f = acknowledge bit clocked into master. g = msb of data clocked into slave. h = lsb of data clocked into slave. i = master pulls data line low. j = acknowledge clocked into slave. k = acknowledge clock pulse. l = stop condition. m = new start condition. figure 3. 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 master. h = lsb of data clocked into master. i = master pulls data line low. j = acknowledge clocked into slave. k = acknowledge clock pulse. l = stop condition. m = new start condition. figure 4. smbus read-timing diagram
max6689 alert response address the smbus alert response interrupt pointer provides quick fault identification for simple slave devices that lack the complex logic needed to be a bus master. upon receiving an interrupt signal, the host master can broadcast a receive byte transmission to the alert response slave address (see the slave addresses sec- tion). then, any slave device that generated an inter- rupt attempts to identify itself by putting its own address on the bus. 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 acknowledgment 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 output latch. if the condition that caused the alert still exists, the max6689 reasserts the alert interrupt at the end of the next conversion. overt overtemperature alarms the max6689 has four overtemperature registers that store remote alarm threshold data for the overt output. overt is asserted when a channel? measured temper- ature is greater than the value stored in the correspond- ing threshold register. overt remains asserted until the temperature drops below the programmed threshold minus 4? hysteresis. an overtemperature output can be used to activate a cooling fan, send a warning, initi- ate clock throttling, or trigger a system shutdown to pre- vent component damage. see table 3 for the por state of the overtemperature threshold registers. command byte functions the 8-bit command byte register (table 3) is the master index that points to the various other registers within the max6689. this register? por state is 0000 0000. configuration byte functions there are three read-write configuration registers (tables 4, 5, and 6) that can be used to control the max6689? operation. configuration 1 register the configuration 1 register (table 4) has several func- tions. bit 7 (msb) is used to put the max6689 either in software standby mode (stop) or continuous conver- sion mode. bit 6 resets all registers to their power-on reset conditions and then clears itself. bit 5 disables the smbus timeout. bit 4 enables more frequent con- versions on channel 1, as described in the adc conversion sequence section. bit 3 enables resistance cancellation on channel 1. see the series resistance cancellation section for more details. the remaining bits of the configuration 1 register are not used. the por state of this register is 0000 0000 (00h). configuration 2 register the configuration 2 register functions are described in table 5. bits [6:0] are used to mask the alert interrupt output. bit 6 masks the local alert interrupt and bits 5 through bit 0 mask the remote alert interrupts. the power-up state of this register is 0000 0000 (00h). configuration 3 register table 6 describes the configuration 3 register. bits 5, 4, 3, and 0 mask the overt interrupt output for channels 6, 5, 4, and 1. the remaining bits, 7, 6, 2, and 1, are reserved. the power-up state of this register is 0000 0000 (00h). status register functions status registers 1, 2, and 3 (tables 7, 8, and 9) indicate which (if any) temperature thresholds have been exceeded and if there is an open-circuit or short-circuit fault detected with the external sense junctions. status register 1 indicates if the measured temperature has exceeded the threshold limit set in the alert registers for the local or remote-sensing diodes. status register 2 indicates if the measured temperature has exceeded the threshold limit set in the overt registers. status register 3 indicates if there is a diode fault (open or short) in any of the remote-sensing channels. bits in the alert status register clear by a successful read, but set again after the next conversion unless the fault is corrected, either by a drop in the measured tem- perature or an increase in the threshold temperature. the alert interrupt output follows the status flag bit. once the alert output is asserted, it can be deasserted by either reading status register 1 or by successfully responding to an alert response address. 7-channel precision temperature monitor 10 ______________________________________________________________________________________ * purchase of i 2 c components from maxim integrated products, inc., or one of its sublicensed associated companies, conveys a license under the philips i 2 c patent rights to use these com- ponents in an i 2 c system, provided that the system conforms to the i 2 c standard specification as defined by philips.
max6689 7-channel precision temperature monitor ______________________________________________________________________________________ 11 register address (hex) por state (hex) read/ write description local 07 00 r read local temperature register remote 1 01 00 r read channel 1 remote temperature register remote 2 02 00 r read channel 2 remote temperature register remote 3 03 00 r read channel 3 remote temperature register remote 4 04 00 r read channel 4 remote temperature register remote 5 05 00 r read channel 5 remote temperature register remote 6 06 00 r read channel 6 remote temperature register configuration 1 41 00 r/w read/write configuration register 1 configuration 2 42 00 r/w read/write configuration register 2 configuration 3 43 00 r/w read/write configuration register 3 status1 44 00 r read status register 1 status2 45 00 r read status register 2 status3 46 00 r read status register 3 local alert high limit 17 5a r/w read/write local alert high-temperature threshold limit register remote 1 alert high limit 11 6e r/w read/write channel 1 remote-diode alert high-temperature threshold limit register remote 2 alert high limit 12 7f r/w read/write channel 2 remote-diode alert high-temperature threshold limit register remote 3 alert high limit 13 64 r/w read/write channel 3 remote-diode alert high-temperature threshold limit register remote 4 alert high limit 14 64 r/w read/write channel 4 remote-diode alert high-temperature threshold limit register remote 5 alert high limit 15 64 r/w read/write channel 5 remote-diode alert high-temperature threshold limit register remote 6 alert high limit 16 64 r/w read/write channel 6 remote-diode alert high-temperature threshold limit register remote 1 overt high limit 21 6e r/w read/write channel 1 remote-diode overtemperature threshold limit register remote 4 overt high limit 24 7f r/w read/write channel 4 remote-diode overtemperature threshold limit register remote 5 overt high limit 25 5a r/w read/write channel 5 remote-diode overtemperature threshold limit register remote 6 overt high limit 26 5a r/w read/write channel 6 remote-diode overtemperature threshold limit register remote 1 extended temperature 09 00 r read channel 1 remote-diode extended temperature register manufacturer id 0a 4d r read manufacturer id table 3. command byte register bit assignment
max6689 in both cases, the alert is cleared even if the fault condi- tion exists, but the alert output reasserts at the end of the next conversion. the bits indicating the fault for the overt interrupt output clear only on reading the status 2 register even if the fault conditions still exist. reading the status 2 register does not clear the overt interrupt out- put. to eliminate the fault condition, either the measured temperature must drop below the temperature threshold minus the hysteresis value (4?), or the trip temperature must be set at least 4? above the current temperature. applications information remote-diode selection the max6689 directly measures the die temperature of cpus and other ics that have on-chip temperature- sensing diodes (see the typical application circuit ) or it can measure the temperature of a discrete diode- connected transistor. effect of ideality factor the accuracy of the remote temperature measure- ments depends on the ideality factor (n) of the remote ?iode?(actually a transistor). the max6689 is opti- mized for n = 1.012. a thermal diode on the substrate of an ic is normally a pnp with the base and emitter brought out the collector (diode connection) grounded. dxp_ must be connected to the anode (emitter) and dxn_ must be connected to the cathode (base) of this pnp. if a sense transistor with an ideality factor other than 1.012 is used, the output data is different from the data obtained with the optimum ideality factor. fortunately, the difference is predictable. assume a remote-diode sensor designed for a nominal ideality 7-channel precision temperature monitor 12 ______________________________________________________________________________________ bit name por state function 7 (msb) stop 0 standby-mode control bit. if stop is set to logic 1, the max6689 stops converting and enters standby mode. 6por0 reset bit. set to logic 1 to put the device into its power-on state. this bit is self- clearing. 5 timeout 0 timeout enable bit. set to logic 0 to enable smbus timeout. 4 fast remote 1 0 channel 1 fast-conversion bit. set to logic 1 to enable fast conversion of channel 1. 3 resistance cancellation 0 resistance cancellation bit. when set to logic 1, the max6689 cancels series resistance in the channel 1 thermal diode. 2 reserved 0 1 reserved 0 0 reserved 0 table 4. configuration 1 register table 5. configuration 2 register bit name por state function 7 (msb) reserved 0 6 mask local alert 0 local alert mask. set to logic 1 to mask local channel alert . 5 mask alert 6 0 channel 6 alert mask. set to logic 1 to mask channel 6 alert . 4 mask alert 5 0 channel 5 alert interrupt mask. set to logic 1 to mask channel 5 alert . 3 mask alert 4 0 channel 4 alert mask. set to logic 1 to mask channel 4 alert . 2 mask alert 3 0 channel 3 alert interrupt mask. set to logic 1 to mask channel 3 alert . 1 mask alert 2 0 channel 2 alert mask. set to logic 1 to mask channel 2 alert . 0 mask alert 1 0 channel 1 alert mask. set to logic 1 to mask channel 1 alert .
factor n nominal is used to measure the temperature of a diode with a different ideality factor n1. the measured temperature t m can be corrected using: where temperature is measured in kelvin and n nomimal for the max6689 is 1.012. as an example, assume you want to use the max6689 with a cpu that has an ideality factor of 1.002. if the diode has no series resistance, the measured data is related to the real temperature as follows: for a real temperature of +85? (358.15k), the mea- sured temperature is +81.46? (354.61k), an error of -3.539?. series resistance cancellation some thermal diodes on high-power ics can have excessive series resistance, which can cause tempera- ture measurement errors with conventional remote tem- perature sensors. channel 1 of the max6689 has a series resistance cancellation feature (enabled by bit 3 of the configuration 1 register) that eliminates the effect of diode series resistance. set bit 3 to 1 if the series resistance is large enough to affect the accuracy of channel 1. the series resistance cancellation function increases the conversion time for channel 1 by 125ms. this feature cancels the bulk resistance of the sensor and any other resistance in series (wire, contact resis- tance, etc.). the cancellation range is from 0 to 100 . discrete remote diodes when the remote-sensing diode is a discrete transistor, its collector and base must be connected together. table 10 lists examples of discrete transistors that are appropriate for use with the max6689. the transistor must be a small-signal type with a relatively high for- ward 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 temperature, the for- ward 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 specifica- tions for forward current gain (50 < ?<150, for exam- ple) indicate that the manufacturer has good process controls and that the devices have consistent v be char- acteristics. manufacturers of discrete transistors do not normally specify or guarantee ideality factor. this is normally not a problem since good-quality discrete transistors tend to have ideality factors that fall within a relatively narrow range. we have observed variations in remote temperature readings of less than ?? with a variety of discrete transistors. still, it is good design practice to verify good consistency of temperature readings with several discrete transistors from any manufacturer under consideration. tt n n tt actual m nominal mm = ? ? ? ? ? ? = ? ? ? ? ? ? = 1 1 012 1 002 1 00998 . . (. ) tt n n m actual nominal = ? ? ? ? ? ? 1 max6689 7-channel precision temperature monitor ______________________________________________________________________________________ 13 table 6. configuration 3 register bit name por state function 7 (msb) reserved 0 6 reserved 0 5 mask overt 6 0 channel 6 remote-diode overt mask bit. set to logic 1 to mask channel 6 overt . 4 mask overt 5 0 channel 5 remote-diode overt mask bit. set to logic 1 to mask channel 5 overt . 3 mask overt 4 0 channel 4 remote-diode overt mask bit. set to logic 1 to mask channel 4 overt . 2 reserved 0 1 reserved 0 0 mask overt 1 0 channel 1 remote-diode overt mask bit. set to logic 1 to mask channel 1 overt .
max6689 unused diode channels if one or more of the remote diode channels is not needed, the dxp and dxn inputs for that channel should either be unconnected, or the dxp input should be connected to v cc . the status register indicates a diode "fault" for this channel and the channel is ignored during the temperature-measurement sequence. it is also good practice to mask any unused channels immediately upon power-up by setting the appropriate bits in the configuration 2 and configuration 3 regis- ters. this will prevent unused channels from causing alert or overt to assert. thermal mass and self-heating when sensing local temperature, the max6689 mea- sures the temperature of the printed-circuit board (pcb) to which it is soldered. the leads provide a good thermal path between the pcb traces and the die. as with all ic temperature sensors, thermal conductivity between the die and the ambient air is poor by compar- ison, making air temperature measurements impracti- cal. because the thermal mass of the pcb is far greater than that of the max6689, the device follows tempera- ture changes on the pcb 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 virtually no effect; the measured temperature of the junction tracks the actual temperature within a conver- sion cycle. when measuring temperature with discrete remote transistors, the best thermal response times are obtained with transistors in small packages (i.e., sot23 or sc70). 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. 7-channel precision temperature monitor 14 ______________________________________________________________________________________ table 7. status 1 register bit name por state function 7 (msb) reserved 0 6 local alert 0 local channel high-alert bit. this bit is set to logic 1 when the local temperature exceeds the temperature threshold limit in the local alert high- limit register. 5 remote 6 alert 0 channel 6 remote-diode high-alert bit. this bit is set to logic 1 when the channel 6 remote-diode temperature exceeds the temperature threshold limit in the remote 6 alert high-limit register. 4 remote 5 alert 0 channel 5 remote-diode high-alert bit. this bit is set to logic 1 when the channel 5 remote-diode temperature exceeds the programmed temperature threshold limit in the remote 5 alert high-limit register. 3 remote 4 alert 0 channel 4 remote-diode high-alert bit. this bit is set to logic 1 when the channel 4 remote-diode temperature exceeds the temperature threshold limit in the remote 4 alert high-limit register. 2 remote 3 alert 0 channel 3 remote-diode high-alert bit. this bit is set to logic 1 when the channel 3 remote-diode temperature exceeds the programmed temperature threshold limit in the remote 3 alert high-limit register. 1 remote 2 alert 0 channel 2 remote-diode high-alert bit. this bit is set to logic 1 when the channel 2 remote-diode temperature exceeds the temperature threshold limit in the remote 2 alert high-limit register. 0 remote 1 alert 0 channel 1 remote-diode high-alert bit. this bit is set to logic 1 when the channel 1 remote-diode temperature exceeds the temperature threshold limit in the remote 1 alert high-limit register.
max6689 7-channel precision temperature monitor ______________________________________________________________________________________ 15 bit name por state function 7 (msb) reserved 0 6 reserved 0 5 remote 6 overt 0 channel 6 remote-diode overtemperature status bit. this bit is set to logic 1 when the channel 6 remote-diode temperature exceeds the temperature threshold limit in the remote 6 overt high-limit register. 4 remote 5 overt 0 channel 5 remote diode overtemperature status bit. this bit is set to logic 1 when the channel 5 remote-diode temperature exceeds the temperature threshold limit in the remote 5 overt high-limit register. 3 remote 4 overt 0 channel 4 remote diode overtemperature status bit. this bit is set to logic 1 when the channel 4 remote-diode temperature exceeds the temperature threshold limit in the remote 4 overt high-limit register. 2 reserved 0 1 reserved 0 0 remote 1 overt 0 channel 1 remote-diode overtemperature status bit. this bit is set to logic 1 when the channel 1 remote-diode temperature exceeds the temperature threshold limit in the remote 1 overt high-limit register. table 8. status 2 register bit name por state function 7 (msb) reserved 0 6 diode fault 6 0 channel 6 remote-diode fault bit. this bit is set to 1 when dxp6 and dxn6 are open circuit or when dxp6 is connected to v cc . 5 diode fault 5 0 channel 5 remote-diode fault bit. this bit is set to 1 when dxp5 and dxn5 are open circuit or when dxp5 is connected to v cc . 4 diode fault 4 0 channel 4 remote-diode fault bit. this bit is set to 1 when dxp4 and dxn4 are open circuit or when dxp4 is connected to v cc . 3 diode fault 3 0 channel 3 remote-diode fault bit. this bit is set to 1 when dxp3 and dxn3 are open circuit or when dxp3 is connected to v cc . 2 diode fault 2 0 channel 2 remote-diode fault bit. this bit is set to 1 when dxp2 and dxn2 are open circuit or when dxp2 is connected to v cc . 1 diode fault 1 0 channel 1 remote-diode fault bit. this bit is set to 1 when dxp1 and dxn1 are open circuit or when dxp1 is connected to v cc . 0 reserved 0 table 9. status 3 register
max6689 adc noise filtering the integrating adc has good noise rejection for low- frequency signals, such as power-supply hum. in envi- ronments with significant high-frequency emi, connect an external 2200pf capacitor between dxp_ and dxn_. 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. high-frequency noise reduction is needed for high-accuracy remote measurements. noise can be reduced with careful pcb layout as dis- cussed in the pcb layout section. slave address table 11 shows the max6689 slave addresses. pcb layout follow these guidelines to reduce the measurement error when measuring remote temperature: 1) place the max6689 as close as is practical to the remote diode. in noisy environments, such as a computer motherboard, this distance 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 pci buses. 2) do not route the dxp-dxn lines next to the deflec- tion coils of a crt. also, do not route the traces across 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. each parallel pair of traces should go to a remote diode. route these traces away from any higher voltage traces, such as +12vdc. leakage currents from pcb contamination must be dealt with carefully since a 20m leakage path from dxp to ground causes about +1? error. if high-voltage traces are unavoidable, connect guard traces to gnd on either side of the dxp-dxn traces (figure 5). 4) route through as few vias and crossunders as pos- sible to minimize copper/solder thermocouple effects. 5) use wide traces when practical. 5mil to 10mil traces are typical. be aware of the effect of trace resis- tance on temperature readings when using long, narrow traces. 6) when the power supply is noisy, add a resistor (up to 47 ) in series with v cc . 7-channel precision temperature monitor 16 ______________________________________________________________________________________ 5?0 mils 5?0 mils 5?0 mils minimum 5?0 mils gnd dxp dxn gnd figure 5. recommended dxp-dxn pcb traces. the two outer guard traces are recommended if high-voltage traces will be near the dxn and dxp traces. manufacturer model no. central semiconductor (usa) cmpt3904 rohm semiconductor (usa) sst3904 samsung (korea) kst3904-tf siemens (germany) smbt3904 zetex (england) fmmt3904ct-nd table 10. remote-sensors transistor manufacturer note: discrete transistors must be diode connected (base shorted to collector). part smbus slave id pin-package max6689ep34 0011 010 20 qsop max6689ep38 0011 100 20 qsop max6689ep9a 1001 101 20 qsop max6689ep9e 1001 111 20 qsop max6689up34 0011 010 20 tssop max6689up38 0011 100 20 tssop max6689up9a 1001 101 20 tssop max6689up9e 1001 111 20 tssop table 11. slave address
twisted-pair and shielded cables use a twisted-pair cable to connect the remote sensor for 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 capacitance 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 approximately +1/2?. max6689 7-channel precision temperature monitor ______________________________________________________________________________________ 17 20 19 18 17 16 15 14 13 1 2 3 4 5 6 7 8 gnd smbclk smbdata dxn2 dxp2 dxn1 dxp1 top view v cc n.c. stby dxn4 dxp4 dxn3 dxp3 12 11 9 10 dxp6 dxn6 dxn5 dxp5 max6689 qsop/tssop + alert overt pin configuration chip information process: bicmos
max6689 7-channel precision temperature monitor 18 ______________________________________________________________________________________ package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) qsop.eps f 1 1 21-0055 package outline, qsop .150", .025" lead pitch
max6689 7-channel precision temperature monitor 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. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 19 2007 maxim integrated products is a registered trademark of maxim integrated products, inc. max6689 package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) tssop4.40mm.eps package outline, tssop 4.40mm body 21-0066 1 1 i revision history pages changed at rev 1: 5, 6, 8, 9, 14, 15, 16, 19

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