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general description the MAX31730 temperature sensor monitors its own tem - perature and the temperatures of three external diode- connected transistors. the operating supply voltage is from 3.0v to 3.6v. resistance cancellation compensates for high series resistance in circuit-board traces and the external thermal diode, while beta compensation corrects for temperature-measurement errors due to low-beta sensing transistors. all temperature channels have programmable temperature thresholds. when the measured temperature of a channel crosses the respective threshold, a status bit is set in the thermal status registers and the open-drain therm output asserts. a highest temperature register allows the master to obtain the temperature of the hottest channel. the 2-wire serial interface accepts smbus protocols (write byte, read byte, send byte, and receive byte) for reading the temperature data and programming the temperature thresholds. any one of eight available slave addresses can be selected using the address selection input (add), which can be connected to ground or con - nected to a grounded resistor. the MAX31730 is specified for a -40c to +125c operat - ing temperature range and is available in a 10-pin max ? and a 12-pin, 3mm x 3mm tdfn package. features and benefts one local and three remote temperature-sensing channels 3.0v to 3.6v operation 12-bit, 0.0625c resolution 1c remote temperature-measurement accuracy (0c to +100c) -64c to +150c remote temperature-measurement range resistance cancellation for remote channels compensation for low beta transistors programmable temperature thresholds smbus/i 2 c-compatible bus interface eight selectable slave addresses applications cpu, fpga, and asic die temperature monitoring servers communications equipment for related parts and recommended products to use with this part, refer to www.maximintegrated.com/MAX31730.related . max is a registered trademark of maxim integrated products, inc. ordering information appears at end of data sheet. v dd dxp1 dxn to master dxp2 dxp3 ic1 +3.3v +3.3v sda add therm gnd scl MAX31730 (10 max) ic2 v dd dxp1 dxn1 to master dxp2 dxn2 dxp3 dxn3 ic1 +3.3v +3.3v sda add therm gnd scl ic2 MAX31730 (12 tdfn) 19-6953; rev 0; 3/14 typical application circuits evaluation kit available MAX31730 3-channel remote temperature sensor
v dd , scl, sda, therm , add ............................ -0.3v to +3.7v all other pins ........................................... -0.3v to (v dd + 0.3v) esd protection (all pins, human body model) .................... 2kv continuous power dissipation (t a = +70c) max (derate at 8.8mw /c above +70c) ............ 707.30mw tdfn (derate 24.4mw/c above +70c) ............... 1951.2mw operating temperature range ......................... -40c to +125c junction temperature ...................................................... +150c storage temperature range ............................ -65c to +150c lead temperature (soldering, 10s) ................................. +300c soldering temperature (reflow) ....................................... +260c max junction-to-ambient thermal resistance ( ja ) ..... 113.1c/w junction-to-case thermal resistance ( jc ) ............... 36c/w tdfn junction-to-ambient thermal resistance ( ja ) .......... 41c/w junction-to-case thermal resistance ( jc ) .............. 8.5c/w (t a = -40c to +125c, unless otherwise noted.) (note 2) (3.0v v dd 3.6v, t a = -40c to +125c, unless otherwise noted) parameter symbol conditions min typ max units voltage supply v dd (note 3) 3.0 3.3 3.6 v input logic 0 v il sda, scl (note 3) -0.3 +0.8 v input logic 1 v ih sda, scl (note 3) 2.2 v dd + 0.3 v c ext (between dxp and dxn) compensation disabled 2200 pf compensation enabled 200 pf parameter symbol conditions min typ max units supply current i dd standby (note 4) 2.5 7 a operating, compensation disabled 700 1200 temperature resolution -0.0625 +0.0625 c remote temperature accuracy t a = 0c to +70c, t rj = 0c to +100c -1 +1 c t a = 0c to +70c, t rj = +100c to +150c -2 +2 t a = -40c to +125c, t rj = -40c to +125c -2.5 +2.5 maxim integrated 2 note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four-layer board. for detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial . absolute maximum ratings stresses beyond those listed under absolute 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 ab solute maximum rating conditions for extended periods may affect device reliability. (note 1) package thermal characteristics recommended operating conditions electrical characteristics MAX31730 3-channel remote temperature sensor www.maximintegrated.com
(3.0v v dd 3.6v, t a = -40c to +125c, timing referenced to v il(max) and v ih(max) , unless otherwise noted) (note 6) (figures 2 and 3) (3.0v v dd 3.6v, t a = -40c to +125c, unless otherwise noted) parameter symbol conditions min typ max units local temperature accuracy t a = 0c to +70c -1 +1 c t a = -20c to +85c -1.5 +1.5 t a = -40c to +125c -2 +2 temperature hysteresis comparator mode only 2 c conversion time per channel compensation disabled 100 ms compensation enabled 150 ms conversion time for all channels compensation disabled 350 ms remote-diode source current i rj high level 180 a low level 12 dxn_ bias voltage beta compensation disabled 0.3 v beta compensation enabled 0.65 por threshold v por v dd rising edge 2.65 2.8 v por threshold hysteresis 110 mv therm output low voltage v ol i sink = 1ma 100 mv i sink = 6ma 300 input leakage current i leak (note 5) 0.01 1 a output high leakage current therm , sda 1 a parameter symbol conditions min typ max units serial-clock frequency f clk 400 khz bus free time between stop and start condition t buf f clk = 400khz 1.3 s repeated start condition setup time t su:sta 0.6 s start condition setup time 90% of scl to 90% of sda, f clk = 400khz 0.6 s start condition hold time t hd:sta 90% of sda to 90% of scl, f clk = 400khz 0.6 s stop condition setup time t su:sto 90% of scl to 90% of sda, f clk = 400khz 0.6 s maxim integrated 3 i 2 c ac electrical characteristics electrical characteristics (continued) MAX31730 3-channel remote temperature sensor www.maximintegrated.com
note 2: limits are 100% production tested at t a = +25c. limits over the operating temperature range and relevant supply voltage range are guaranteed by design and characterization. typical values are not guaranteed. note 3: all voltages referenced to ground. note 4: sda = scl = v dd . note 5: applies to pins sda, scl, and add. note 6: all timing specifications guaranteed by design. note 7: a master device must provide a hold time of at least 300ns for the sda signal to bridge the undefined region of scls falling edge. note 8: holding the sda line low for a time greater than t timeout causes the device to reset sda to the idle state of the serial-bus communication (sda set high). (3.0v v dd 3.6v, t a = -40c to +125c, timing referenced to v il(max) and v ih(max) , unless otherwise noted) (note 6) (figures 2 and 3) parameter symbol conditions min typ max units clock low period t low 10% to 10% 1 s clock high period t high 90% to 90% 1 s data-in hold time t hd:dat (note 7) 0.3 s data-in setup time t su:dat 100 ns receive clock/data rise time t r 300 ns receive clock/data fall time t f 300 ns pulse width of spike suppressed t sp 0 50 ns bus timeout t timeout (note 8) 25 45 ms maxim integrated 4 i 2 c ac electrical characteristics (continued) MAX31730 3-channel remote temperature sensor www.maximintegrated.com
(3.0v v dd 3.6v, t a = +25c, unless otherwise noted.) 400 500 600 700 800 900 1000 -40 10 60 110 active current (a) temperature ( c) v dd = 3.6v active current vs temperature toc01 beta compensation disabled v dd = 3.3v v dd = 3.0v 0 1 2 3 4 5 6 -40 10 60 110 standby current (a) temperature ( c) v dd = 3.6v standby current vs temperature toc03 v dd = 3.3v v dd = 3.0v 400 600 800 1000 1200 1400 1600 1800 -40 10 60 110 active current (a) temperature ( c) v dd = 3.6v active current vs temperature toc02 v dd = 3.3v beta compensation enabled; beta = 0.1 v dd = 3.0v -0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 -40 10 60 110 temperature error ( c) temperature ( c ) internal temperature error vs. temperature toc04 v dd = 3.6v v dd = 3.3v v dd = 3.0v data taken in bath limited to +90 c maxim integrated 5 typical operating characteristics MAX31730 3-channel remote temperature sensor www.maximintegrated.com
10 2 3 4 5 9 8 7 6 s d a a d d t h e r m g n d dxp3 dxp2 dxn dxp1 max top view + MAX31730 1 s cl v dd v dd dxp1 dxn1 dxp2 dxn2 dxp3 s cl s d a a d d g n d dxn3 t h e r m ma31730 top view 1 + 3 4 2 tdfn 3mm x 3mm 5 6 11 9 8 7 10 12 pin name function max tdfn 1 1 v dd supply voltage input. bypass to gnd with a 0.1f capacitor. 2 2 dxp1 combined current source and adc positive input for channel 1 remote diode. connect dxp1 to the anode of a remote-diode-connected, temperature-sensing transistor. leave dxp1 unconnected or connect to dxn or dxn1 if the channel 1 remote diode is not used. connect a capacitor (see the c ext specifcation in the electrical characteristic table) between dxp1 and dxn or dxn1 for noise fltering. 3 dxn1 cathode input for channel 1 remote diode. connect the cathode of the channel 1 remote-diode-connected transistor to dxn1. if the channel 1 remote transistor is a substrate pnp (e.g., on a cpu or asic die), connect the base of the pnp to dxn1. leave dxn1 unconnected or connect to dxp1 if a remote diode is not used. connect a capacitor (see the c ext specifcation in the electrical characteristic table) between dxp1 and dxn1 for noise fltering. 3 dxn shared cathode input for remote-diode channels. connect the cathodes of the channel remote-diode-connected transistors to dxn. if a remote transistor is a substrate pnp (e.g., on a cpu or asic die), connect the base of the pnp to dxn. connect a capacitor (see the c ext specifcation in the electrical characteristic table) between dxp_ and dxn for noise fltering. maxim integrated 6 pin description pin confgurations MAX31730 3-channel remote temperature sensor www.maximintegrated.com
pin name function max tdfn 4 4 dxp2 combined current source and adc positive input for channel 2 remote diode. connect dxp2 to the anode of a remote-diode-connected, temperature-sensing transistor. leave dxp2 unconnected or connect to dxn or dxn2 if a remote diode is not used. connect a capacitor (see the c ext specifcation in the electrical characteristic table) between dxp2 and dxn or dxn2 for noise fltering. 5 dxn2 cathode input for channel 2 remote diode. connect the cathode of the channel 2 remote-diode-connected transistor to dxn2. if the channel 2 remote transistor is a substrate pnp (e.g., on a cpu die), connect the base of the pnp to dxn2. leave dxn2 unconnected or connect to dxp2 if a remote diode is not used. connect a capacitor (see the c ext specifcation in the electrical characteristic table) between dxp2 and dxn2 for noise fltering. 5 6 dxp3 combined current source and adc positive input for channel 3 remote diode. connect dxp3 to the anode of a remote-diode-connected, temperature-sensing transistor. leave dxp3 unconnected or connect to dxn or dxn3 if a remote diode is not used. connect a capacitor (see the c ext specifcation in the electrical characteristic table) between dxp3 and dxn or dxn3 for noise fltering. 7 dxn3 cathode input for channel 3 remote diode. connect the cathode of the channel 3 remote-diode-connected transistor to dxn3. if the channel 3 remote transistor is a substrate pnp (e.g., on a cpu die), connect the base of the pnp to dxn3. leave dxn3 unconnected or connect to dxp3 if a remote diode is not used. connect a capacitor (see the c ext specifcation in the electrical characteristic table) between dxp3 and dxn3 for noise fltering. 6 8 gnd ground 7 9 therm active-low, open-drain over/undertemperature output. can also be used as a smbus alert output by setting the device to interrupt mode using the confguration register. when enabled, therm asserts low when the temperature of any channel goes beyond a programmed threshold. 8 10 add address-select input. sampled at power-up. one of eight possible addresses can be selected by connecting add to gnd, or connecting add to a grounded resistor. 9 11 sda i 2 c/smbus serial-data input/output. connect sda to a pullup resistor. 10 12 scl i 2 c/smbus serial-clock input. connect scl to a pullup resistor. maxim integrated 7 pin description (continued) MAX31730 3-channel remote temperature sensor www.maximintegrated.com
detailed description the MAX31730 is a precision temperature monitor that features one local and three remote temperature-sensing channels, with programmable temperature thresholds for each channel. communication with the device is achieved through the smbus/i 2 c-compatible serial interface and over/undertemperature-detection output ( therm ). the therm output asserts if the software-programmed tem - perature thresholds are exceeded. therm normally operates in comparator mode and can be connected to a fan, system shutdown, or other thermal-management circuitry. it can also operate in interrupt mode to serve as a smbus alert interrupt. adc conversion sequence the device starts the conversion sequence by measuring the temperature on remote channel 1, followed by remote channel 2, remote channel 3, and the local channel. the conversion result for each enabled channel is stored in the corresponding temperature data register. no conver - sion is performed on any remote channel that does not have a diode connected, whose dxp_ - dxn_ inputs are shorted together, or that has a short between dxp_ and v dd , dxp_ and gnd, or dxn_ and v dd , or if the chan - nel is not enabled in the highest temperature enable register. see the register 36h: diode fault status section for additional details. v dd scl sda add gnd mux ref smbus / i 2 c interface adc + - current source register bank configuration bytes remote temperatures local temperatures therm smbus alert threshold local temperature thermal thresholds alert response address alarm MAX31730 dxn1 dxp1 dxn2 dxp2 dxn3 dxp3 maxim integrated 8 block diagram MAX31730 3-channel remote temperature sensor www.maximintegrated.com
series-resistance cancellation some thermal diodes on high-power ics have excessive series resistance that can cause temperature-measure - ment errors when used with conventional remote temper - ature sensors. external channels 1C3 of the device have a series-resistance cancellation feature that eliminates the effect of diode series resistance and interconnection resistance. the cancellation range is from 0 to 300. series-resistance cancellation is always enabled. low-power standby mode enter software-standby mode by setting the stop bit to 1 in the configuration register. software-standby mode disables the adc and reduces the supply current to approximately 2.5a. during software standby, data is retained in memory and the bus interface is active and listening for commands. if a start condition is recognized, activity on the bus causes the supply current to increase. if a standby command is received while a conversion is in progress, the conversion cycle is finished, then the device enters shutdown, and the temperature registers are updated. smbus digital interface the device is smbus 2.0 compatible and supports four standard smbus protocols: write byte, read byte, send byte, and receive byte, as well as multibyte reads and writes ( figure 1 ). the shorter receive-byte protocol allows quicker transfers, provided that the correct 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 register byte without informing the first master. figure 2 is the smbus write timing diagram and figure 3 is the smbus read timing diagram. the write-byte format consists of the master transmitting the slave address, followed by the address for the target register, followed by the 8 bits of data to be written to the target register. to write multiple bytes to two or more contiguous registers, write a new byte after each ack. the register address then increments after each byte is written. end the transaction with a stop condition. the read-byte format consists of the master transmitting the slave address followed by the address for the register to be read. the master then begins a new transaction by sending the slave address again, after which the slave returns the data from the selected register. to read multiple bytes from two or more contiguous registers, continue reading after each ack. the register address then increments after each byte is read. conclude the overall transaction with a nack and a stop condition. when the first byte of a 2-byte temperature value is read, the device prevents updates of the second bytes contents until the second byte has been read. if the second byte has not been read within a smbus timeout period (nominally 35ms), it is again allowed to update. the send-byte format can be used to transmit a regis - ter address without a transfer of data. it consists of the master transmitting the slave address followed by the address of the target register. the receive-byte format can be used to read data from a register that was previously selected. it consists of the master transmitting the slave address, after which the slave returns the data from the register that was previous - ly selected. after this command completes, the address pointer does not increment. maxim integrated 9 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
figure 1. i 2 c/smbus format s address wr ack ack p data ack register 7 bits 1 8 bits 8 bits slave address: equivalent to chip-select line of a 3-wire interface data byte: data goes into the register set by the register byte write-byte format s address address wr ack ack p s rd ack /// data register 7 bits 7 bits 8 bits 8 bits read-byte format slave address: equivalent to chip select line register byte: selects which register you are reading from s p address wr ack ack register 7 bits 8 bits send-byte format register byte: sends register address with no data. s p 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 register byte s = start condition p = stop condition shaded = slave transmission /// = not acknowledged multiple write-byte format stop /// s address address wr ack ack s rd ack ... ... register 7 bits 7 bits 8 bits data data ack ack data ... ... ... ... 8 bits 8 bits 8 bits multiple read-byte format stop s address wr ack ack ack data ... ... register 7 bits 8 bits 8 bits data data ack ack ack data ... ... ... ... 8 bits 8 bits 8 bits maxim integrated 10 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
alert response address (ara) the smbus alert response interrupt pointer provides quick fault identification for simple slave devices that lack the complex logic necessary to be a bus master. upon receiving an interrupt signal, the host master can broad - cast a receive-byte transmission to the alert response slave address (19h). then, any slave device that gener - ated an interrupt 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 therm pin 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 device reasserts the interrupt at the end of the next conversion. the device responds to the ara only when in interrupt mode. interrupt mode thermal interrupts occur when the local or remote temperature reading crosses a user-programmable high thermal limit or a low thermal limit. the therm interrupt output signal can be cleared by reading the status register associated with the fault or by successfully responding to an ara transmission by the master. in both cases, the thermal fault is cleared but is reasserted at the end of the next conversion if the fault condition still exists. the interrupt does not halt automatic conversions. the therm output is open drain so that multiple devices can share a common interrupt line. all thermal interrupts can be masked using the therm mask register. interrupt mode can be selected by writing bit 4 in the configuration register to a 0. figure 2. smbus/i 2 c write timing diagram figure 3. smbus/i 2 c read timing diagram scl a = start condition b = msb of address clocked into slave c = lsb of address clocked into slave d = r / w bit clocked into slave a b c d e f g h i j sda t su:sta t hd:sta t low t high t buf l m k e = slave pulls sda line low f = acknowledge bit clocked into master g = msb of data clocked into slave h = lsb of data clocked into slave i = slave pulls sda low j = acknowledge clocked into master k = acknowledge clock pulse l = stop condition m = new start condition t su:dat t su:sto scl a b c d e f g h i sda t su:sta t hd:sta t low t high 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 sda line low j k f = acknowledge bit clocked into master g = msb of data clocked into master h = lsb of data clocked into master i = acknowledge clock pulse j = stop condition k = new start condition t su:dat t hd:dat t buf t su:sto maxim integrated 11 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
comparator mode selecting comparator mode in the configuration register causes the therm output to assert based on a tempera - ture measurement exceeding a trip threshold value, just as in interrupt mode. however, in comparator mode, the output deasserts automatically when the temperature crosses the threshold back into the acceptable range. a 2c hysteresis is applied in comparator mode, so clearing the therm output in this mode requires the temperature to be 2c less than the high thermal limit and 2c greater than the low thermal limit. temperature register format temperature data is stored in the temperature, limit, and reference temperature registers. the temperature data format is 12 bits, twos complement, and the register is read out in 2 bytes: an upper byte and a lower byte. bits d[15:0] contain the temperature data, with the lsb repre - senting 0.0625c and the msb representing the sign bit (see table 1 ). the msb is transmitted first. in addition to the normal twos-complement temperature data format, the device offers an optional extended data format that allows temperatures equal to or greater than +127.9375c to be read. in the extended format (selected by bit 1 of the configuration register, 13h), the measured temperature is the value in the temperature register plus 64c, as shown in table 2 . note: when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not auto - matically translated by toggling the extended format bit. table 1. temperature, reference temperature, thermal-limit register definition table 2. temperature register data format upper byte lower byte d15 d14 d13 d12 d11 d10 d9 d8 d7 d6 d5 d4 d3 d2 d1 d0 sign bit msb 64c 2 6 32c 2 5 16c 2 4 8c 2 3 4c 2 2 2c 2 1 1c 2 0 0.5c 2 -1 0.25c 2 -2 0.125c 2 -3 0.0625 2 -4 0 0 0 0 actual temperature (c) normal format extended format binary hex binary hex +150 0111 1111 1111 0000 0x7ff0 0101 0110 0000 0000 0x5600 +128 0111 1111 1111 0000 0x7ff0 0100 0000 0000 0000 0x4000 +127 0111 1111 0000 0000 0x7f00 0011 1111 0000 0000 0x3f00 +125 0111 1101 0000 0000 0x7d00 0011 1101 0000 0000 0x3d00 +64 0100 0000 0000 0000 0x4000 0000 0000 0000 0000 0x0000 +25 0001 1001 0000 0000 0x1900 1101 1001 0000 0000 0xd900 +0.5 0000 0000 1000 0000 0x0080 1100 0000 1000 0000 0xc080 0 0000 0000 0000 0000 0x0000 1100 0000 0000 0000 0xc000 -0.5 1111 1111 1000 0000 0xff80 1011 1111 1000 0000 0xbf80 -25 1110 0111 0000 0000 0xe700 1010 0111 0000 0000 0xa700 -55 1100 1001 0000 0000 0xc900 1000 1001 0000 0000 0x8900 -64 1100 0000 0000 0000 0xc000 1000 0000 0000 0000 0x8000 diode fault 0000 0000 0000 0000 0x0000 0000 0000 0000 0000 0x0000 maxim integrated 12 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
temperature channel enable register the temperature channel enable register selects which temperature-sensing channels are enabled. channels not selected are skipped during the temperature-conversion cycle and diode fault detection is not performed on them. if a channel is deselected while a thermal or diode fault is indicated in the corresponding fault register, the fault bit(s) remain asserted until the register contents are read, and then do not reassert until the channel is again enabled and a fault detected. highest temperature registers the highest temperature registers (10h and 11h) work with the reference temperature registers (40h through 47h) value for each temperature channel. the reference temperature registers can effectively serve as an offset temperature margin, or their contents can simply be set to zero. after each temperature conversion, the reference temperature value is subtracted from the measured tem - perature for the corresponding channel (e.g., remote 2 tem - perature minus remote 2 reference temperature), and the result is compared to the most recent results for the other channels. the highest of all these values is loaded into the reference temperature register. highest temperature enable register the highest temperature enable register selects the temperature channels from which the contents of the highest temperature register are obtained (see table 4 ). table 3. temperature channel enable register (35h) table 4. highest temperature enable register (12h) bit name por value function 7 (msb) reserved 0 reserved. 6 reserved 0 reserved. 5 reserved 0 reserved. 4 reserved 0 reserved. 3 remote 3 1 channel 3 enable bit. set this bit to logic 1 to enable temperature conversions and diode fault detection for remote channel 3. 2 remote 2 1 channel 2 enable bit. set this bit to logic 1 to enable temperature conversions and diode fault detection for remote channel 2. 1 remote 1 1 channel 1 enable bit. set this bit to logic 1 to enable temperature conversions and diode fault detection for remote channel 1. 0 local 1 local temperature channel enable bit. set this bit to logic 1 to enable temperature conversions for the local channel. bit name por value function 7 (msb) reserved 1 reserved. 6 reserved 1 reserved. 5 reserved 1 reserved. 4 reserved 1 reserved. 3 remote 3 1 channel 3 select bit. set to logic 1 to use remote channel 3 in determining the highest temperature. 2 remote 2 1 channel 2 select bit. set to logic 1 to use remote channel 2 in determining the highest temperature. 1 remote 1 1 channel 1 select bit. set to logic 1 to use remote channel 1 in determining the highest temperature. 0 local 1 local select bit. set to logic 1 to use local channel in determining the highest temperature. maxim integrated 13 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
thermal-limit registers the thermal limit registers (20h through 27h) store over - temperature and undertemperature thermal-threshold values. access to these registers is provided through the i 2 c/smbus-compatible interface. alarms are masked at power-up. if a threshold is crossed, a bit is set in the thermal status registers (40h through 47h) to indicate the thermal fault. the therm pin is also asserted unless the channel is masked using the therm mask register. confguration register the configuration register ( table 5 ) has several functions. bit 7 (msb) is used to put the device either in software- standby mode (stop) or continuous-conversion mode. in standby mode, the adc is shut down and the supply current reduced. the bus remains active. bit 6 resets all registers to their por conditions and then clears itself. bit 5 disables the bus timeout function. bit 4 selects whether the therm output functions as an interrupt or as a comparator. bits 2 and 3 enable the fault queue, which sets the number of consecutive thermal faults required before asserting the thermal status bits and the therm output. bit 1 selects the extended range temperature data format ( table 2 ), which allows reading temperature values of 127.9375c or greater. when set to 1, bit 0 begins a single conversion on all enabled temperature channels. this one- shot function can be enabled only when in stop mode. table 5. configuration register (13h) bit name por value function 7 (msb) stop 0 standby-mode control bit. setting stop to 1 disables the adc and reduces supply current to 2.5a. 6 por 0 power-on-reset bit. set to logic 1 to enter the power-on state. this bit is self-clearing. 5 timeout 0 timeout enable bit. set to logic 0 to enable smbus timeout. 4 interrupt/ comparator 1 interrupt/comparator mode-select bit. set to logic 1 to select comparator mode for the therm output. 3 fault queue 0 selects the number of consecutive faults needed to assert the thermal status bits and therm output. 00 = 1; 01 = 2; 10 = 4; 11 = 6. 2 0 1 extrange 0 extended-range enable bit. set bit 1 to logic 1 to set the temperature, limit, and reference data range to maximum reportable temperature of +127.9375c. set bit 1 to logic 0 to set the data range to a maximum reportable temperature of +191.9375c. 0 one shot 0 writing 1 to this bit initiates a single cycle of temperature conversions. all other bits in the confguration register are ignored, and bit 0 automatically resets to 0. one shot can only be enabled in stop mode. maxim integrated 14 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
therm mask register the trm mask register functions are described in table 6 . bits [3:0] are used to mask the pin output. bit 0 masks assertion of trm due to the local channel thermal faults and the remaining bits mask the remote thermal faults. the power-up state of this register is 0000 0000 (00h). status register functions the status registers indicate temperature or diode fault status. the thermal high status register indicates whether a measured local or remote temperature has exceeded the associated threshold limit set in the associated thermal high status register. the thermal low status register indicates whether the measured temperature has fallen below the threshold limit set in the thermal low status register for the local or remote- sensing diodes. the diode fault status register indicates whether there is a diode fault (open or short) in any of the remote-sensing channels. bits in the thermal status registers are cleared by a successful read, but set again after the next conversion unless the fault is corrected, either by a change in the measured temperature or by a change in the threshold temperature. when in comparator mode, reading the status registers has no effect on the trm output state; the state depends on the current temperature, threshold, and mask values. similarly, bits in the diode fault status register are cleared by a successful read, but set again after the next conversion if the fault is still in effect. in interrupt mode, the output follows the status bits for all unmasked channels. once the out - put is asserted while in interrupt mode, it can be deas - serted either by reading the thermal status register or by successfully responding to an ara. in both cases, the pin is cleared even if the fault condition remains in effect, but the trm output reasserts at the end of the next conversion if the fault condition is still present. table 6. therm mask register (34h) bit name por value function 7(msb) reserved 0 reserved. 6 reserved 0 reserved. 5 reserved 0 reserved. 4 reserved 0 reserved. 3 remote 3 0 channel 3 remote mask bit. set to logic 1 to mask assertion of trm due to remote channel 3 thermal fault. 2 remote 2 0 channel 2 remote mask bit. set to logic 1 to mask assertion of trm due to remote channel 2 thermal fault. 1 remote 1 0 channel 1 remote mask bit. set to logic 1 to mask assertion of trm due to remote channel 1 thermal fault. 0 local 0 local mask bit. set to logic 1 to mask assertion of due to local sensor thermal fault. maxim integrated 15 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
table 7. thermal high status register (32h) table 8. thermal low status register (33h) bit name por value function 7 (msb) reserved 0 reserved. 6 reserved 0 reserved. 5 reserved 0 reserved. 4 reserved 0 reserved. 3 remote 3 0 channel 3 remote-diode high thermal bit. this bit is set to logic 1 when the channel 3 remote-diode temperature exceeds the threshold in the remote 3 thermal high limit registers. 2 remote 2 0 channel 2 remote-diode high thermal bit. this bit is set to logic 1 when the channel 2 remote-diode temperature exceeds the threshold in the remote 2 thermal high limit registers. 1 remote 1 0 channel 1 remote-diode high thermal bit. this bit is set to logic 1 when the channel 1 remote-diode temperature exceeds the threshold in the remote 1 thermal high limit registers. 0 local 0 local channel high thermal bit. this bit is set to logic 1 when the local temperature exceeds the threshold in the local thermal high limit registers. bit name por value function 7 (msb) reserved 0 reserved. 6 reserved 0 reserved. 5 reserved 0 reserved. 4 reserved 0 reserved. 3 remote 3 0 channel 3 remote-diode low thermal bit. this bit is set to logic 1 when the channel 3 remote-diode temperature is less than the threshold in the thermal low limit registers. 2 remote 2 0 channel 2 remote-diode low thermal bit. this bit is set to logic 1 when the channel 2 remote-diode temperature is less than the threshold in the thermal low limit registers. 1 remote 1 0 channel 1 remote-diode low thermal bit. this bit is set to logic 1 when the channel 1 remote-diode temperature is less than the threshold in the thermal low limit registers. 0 local 0 local channel low thermal bit. this bit is set to logic 1 when the local temperature is less than the threshold in the thermal low limit registers. maxim integrated 16 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
diode fault detection if a remote channels dxp_ and dxn_ inputs are uncon - nected or are shorted to each other, to ground, or to the supply voltage, the device detects a diode fault. a diode fault does not cause therm to assert and does not allow an overtemperature or undertemperature event to be detected for the affected channel. a bit in the diode fault status register (36h) corresponding to the channel is set to 1 and the temperature data for the channel is stored as 0c (0000h in normal format). a period of approximately 3ms at the beginning of each channels temperature conversion cycle is dedicated to diode fault detection. once a diode fault is detected, the temperature conversion for that channel is abandoned and fault detection/temperature conversion begins on the next channel in the conversion sequence. see the register 36h: diode fault status section. effect of ideality factor the accuracy of the remote temperature measurements depend on the ideality factor (n) of the remote diode (actually a diode-connected transistor). the default value for the MAX31730 is n = 1.008 (channels 1C3). a thermal diode on the substrate of an external ic is normally a pnp, with the base and emitter brought out and the collector grounded. dxp_ must be connected to the anode (emit - ter) and dxn_ must be connected to the cathode (base) of this pnp. if a sense transistor with an ideality factor other than 1.008 is used, the output data will be different from the data obtained with the optimum ideality factor. if necessary, a different ideality factor value can be chosen using the custom ideality factor register ( table 9 ). the custom ideality enable register ( table 10 ) allows each channel to have the default ideality of 1.008 or the value selected in the custom ideality factor register. note that any change in the ideality selections occur on subsequent conversions; current temperature register values do not change until a new conversion has completed. table 9. custom ideality factor register (14h) selection (hex) ideality factor 0x00 0.9844 0x01 0.9853 0x02 0.9863 0x03 0.9873 0x04 0.9882 0x05 0.9892 0x06 0.9902 0x07 0.991 0x08 0.9921 0x09 0.9931 0x0a 0.9941 0x0b 0.9950 0x0c 0.9960 0x0d 0.9970 0x0e 0.9980 0x0f 0.9990 0x10 1.0000 0x11 1.0010 0x12 1.0020 0x13 1.0030 0x14 1.0040 0x15 1.0050 selection (hex) ideality factor 0x16 1.0060 0x17 1.0070 0x18 (default) 1.0080 0x19 1.0090 0x1a 1.0100 0x1b 1.0110 0x1c 1.0120 0x1d 1.0130 0x1e 1.0141 0x1f 1.0151 0x20 1.0161 0x21 1.0171 0x22 1.0182 0x23 1.0192 0x24 1.0202 0x25 1.0213 0x26 1.0223 0x27 1.0233 0x28 1.0244 0x29 1.0254 0x2a 1.0265 0x2b 1.0275 maxim integrated 17 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
table 9. custom ideality factor register (14h) (continued) table 10. custom ideality enable register (15h) selection (hex) ideality factor 0x2c 1.0286 0x2d 1.0296 0x2e 1.0307 0x2f 1.0317 0x30 1.0328 0x31 1.0338 0x32 1.0349 0x33 1.0360 0x34 1.0370 0x35 1.0381 0x36 1.0392 selection (hex) ideality factor 0x37 1.0402 0x38 1.0413 0x39 1.0424 0x3a 1.0435 0x3b 1.0445 0x3c 1.0456 0x3d 1.0467 0x3e 1.0478 0x3f 1.0489 0x40 not valid bit name por value function 7 (msb) reserved 0 reserved. 6 reserved 0 reserved. 5 reserved 0 reserved. 4 reserved 0 reserved. 3 remote 3 0 channel 3 remote-diode custom ideality enable bit. write 0 to this bit to select ideality factor = 1.008 for this channel. write 1 to this bit to select ideality factor determined by the custom ideality factor register. 2 remote 2 0 channel 2 remote-diode custom ideality enable bit. write 0 to this bit to select ideality factor = 1.008 for this channel. write 1 to this bit to select ideality factor determined by the custom ideality factor register. 1 remote 1 0 channel 1 remote-diode custom ideality enable bit. write 0 to this bit to select ideality factor = 1.008 for this channel. write 1 to this bit to select ideality factor determined by the custom ideality factor register. 0 reserved 0 reserved. maxim integrated 18 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
beta compensation beta compensation corrects for errors caused by low beta-sensing transistors. note: it applies only to pnp transistors with their collectors grounded and their bases and emitters connected to dxn_ and dxp_, respectively (see figure 4 ). select the remote channels for which beta compensation are active using the beta compensation enable register ( table 11 ). note that any changes to this register do not change the results currently in the tem - perature registers or temperature conversion in progress; changes affect subsequent conversion results. before beginning a temperature measurement with beta compensation enabled, the device first measures the beta of the target transistor, and then adjusts the drive current level to produce accurate collector current ratios. the beta value registers ( table 12 ) for the three remote channels contain the minimum beta values for the corre - sponding transistors. if a target transistor has a beta less than 0.09, tempera - ture measurement does not work reliably and a tempera - ture measurement is not initiated for that transistor. the diode fault bit is set for the corresponding channel and the temperature registers updated with 0000h. if an attempt at temperature measurement is desired for that remote channel, set the associated beta compensation enable bit to 0. note that if beta compensation is enabled, the series resistance in the diode path must be minimized as the series resistance cancellation circuitry will interfere with the beta compensation. noise filter in noisy environments, it can be useful to average the results of multiple temperature conversion results. use the filter enable register ( table 13 ) to average the previ - ous four conversions to determine the value stored in the temperature registers. even when enabled, averaging occurs when performing a one-shot conversion sequence (selected by bit 0 in the configuration register), so caution should be exercised when long delays occur between one- shot conversions. note that filtering begins after enabling the filter; the current register contents do not change. table 11. beta compensation enable register (19h) figure 4. pnp configuration for use with beta compensation. bit name por value function 7 (msb) reserved 0 reserved. 6 reserved 0 reserved. 5 reserved 0 reserved. 4 reserved 0 reserved. 3 remote 3 0 channel 3 beta compensation enable bit. set this bit to logic 1 to enable beta compensation for remote channel 3. set this bit to logic 0 to disable beta compensation. 2 remote 2 0 channel 2 beta compensation enable bit. set this bit to logic 1 to enable beta compensation for remote channel 2. set this bit to logic 0 to disable beta compensation. 1 remote 1 0 channel 1 beta compensation enable bit. set this bit to logic 1 to enable beta compensation for remote channel 1. set this bit to logic 0 to disable beta compensation. 0 reserved 0 reserved. dxp dxn maxim integrated 19 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
table 12. beta compensation values (registers 1ah, 1bh, and1ch) (read only) table 13. filter enable register (18h) value (hex) bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 beta (min) 0 (default) reserved reserved reserved reserved 0 0 0 0 0.67 1 reserved reserved reserved reserved 0 0 0 1 0.50 2 reserved reserved reserved reserved 0 0 1 0 0.36 3 reserved reserved reserved reserved 0 0 1 1 0.30 4 reserved reserved reserved reserved 0 1 0 0 0.25 5 reserved reserved reserved reserved 0 1 0 1 0.20 6 reserved reserved reserved reserved 0 1 1 0 0.15 7 reserved reserved reserved reserved 0 1 1 1 0.13 8 reserved reserved reserved reserved 1 0 0 0 0.11 9 reserved reserved reserved reserved 1 0 0 1 0.09 f reserved reserved reserved reserved 1 1 1 1 low b fault bit name por value function 7 (msb) reserved 0 reserved. 6 reserved 0 reserved. 5 reserved 0 reserved. 4 reserved 0 reserved. 3 remote 3 0 channel 3 filter enable bit. set this bit to logic 1 to enable flter for remote channel 3. set this bit to logic 0 to disable flter. 2 remote 2 0 channel 2 filter enable bit. set this bit to logic 1 to enable flter for remote channel 2. set this bit to logic 0 to disable flter. 1 remote 1 0 channel 1 filter enable bit. set this bit to logic 1 to enable flter for remote channel 1. set this bit to logic 0 to disable flter. 0 reserved 0 reserved. maxim integrated 20 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
offset registers if desired, an offset value can be applied to the data in any selected temperature channel. select the offset value using the custom offset register ( table 14 ). the resolu - tion of the custom offset value is 0.125c, and the msb is 16c. the temperature offset is calculated using the following equation: -14.875c + b[7:0]/8 = temperature offset the resulting offset range is -14.875c to +17c. with a default power-on value of 77h, the device has a default temperature offset of 0c. choose the temperature channels to which custom off - set is applied using the custom offset enable register ( table 15 ). the offset value does not affect the value in the highest temperature registers. table 14. custom offset register (16h) table 15. custom offset enable register (17h) bit name por state function 7 (msb) 16c 0 digital offset (weighted). 6 8c 1 digital offset (weighted). 5 4c 1 digital offset (weighted). 4 2c 1 digital offset (weighted). 3 1c 0 digital offset (weighted). 2 0.5c 1 digital offset (weighted). 1 0.25c 1 digital offset (weighted). 0 0.125c 1 digital offset (weighted). bit name por state function 7 (msb) reserved 0 reserved. 6 reserved 0 reserved. 5 reserved 0 reserved. 4 reserved 0 reserved. 3 remote 3 0 remote 3 offset enable bit. set to logic 1 to enable offset in the custom offset register. 2 remote 2 0 remote 2 offset enable bit. set to logic 1 to enable offset in the custom offset register. 1 remote 1 0 remote 1 offset enable bit. set to logic 1 to enable offset in the custom offset register. 0 reserved 0 reserved. maxim integrated 21 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register map register address (hex) por value (hex) read/ write description local temperature msb 00 00 r read local temperature msb local temperature lsb 01 00 r read local temperature lsb remote 1 temperature msb 02 00 r read channel 1 remote temperature msb remote 1 temperature lsb 03 00 r read channel 1 remote temperature lsb remote 2 temperature msb 04 00 r read channel 2 remote temperature msb remote 2 temperature lsb 05 00 r read channel 2 remote temperature lsb remote 3 temperature msb 06 00 r read channel 3 remote temperature msb remote 3 temperature lsb 07 00 r read channel 3 remote temperature lsb highest temperature msb 10 00 r highest current temperature value msb. value in highest temperature register is the greater of all (temperature channel value minus the channel reference temperature value). highest temperature lsb 11 00 r highest current temperature value lsb. value in highest temperature register is the greater of all (temperature channel value minus the channel reference temperature value). highest temperature enable 12 0f r/w selects which channels are used in determining contents of highest temperature registers. confguration 13 10 r/w standby, por, timeout, extended range, comparator/ interrupt mode, one-shot, and flter. custom ideality factor 14 18 r/w select a custom ideality factor for remote-sensing diodes. custom ideality enable 15 00 r/w select the nominal ideality (1.008) or the custom ideality for each remote channel. custom offset 16 77 r/w select an offset value for temperature measurement. the device default is -14.875c, with a programmed value of +14.875c, which leaves a summed offset of 0c default from factory/por. custom offset enable 17 00 r/w enable/disable the custom offset temperature value for each channel. maxim integrated 22 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register map (continued) register address (hex) por value (hex) read/ write description filter enable 18 00 r/w enable/disable flter for each remote channel (should be disabled when not in constant conversion mode). beta compensation enable 19 00 r/w enable/disable beta compensation for each remote channel. beta value channel 1 1a 00 r contains the beta compensation value for channel 1. beta value channel 2 1b 00 r contains the beta compensation value for channel 2. beta value channel 3 1c 00 r contains the beta compensation value for channel 3. local thermal high limit msb 20 7f r/w read/write local thermal high-temperature threshold limit msb. local thermal high limit lsb 21 00 r/w read/write local thermal high-temperature threshold limit lsb. remote 1 thermal high limit msb 22 7f r/w read/write remote channel 1 thermal high-temperature threshold limit msb. remote 1 thermal high limit lsb 23 00 r/w read/write remote channel 1 thermal high-temperature threshold limit lsb. remote 2 thermal high limit msb 24 7f r/w read/write remote channel 2 thermal high-temperature threshold limit msb. remote 2 thermal high limit lsb 25 00 r/w read/write remote channel 2 thermal high-temperature threshold limit lsb. remote 3 thermal high limit msb 26 7f r/w read/write remote channel 3 thermal high-temperature threshold limit msb. remote 3 thermal high limit lsb 27 00 r/w read/write remote channel 3 thermal high-temperature threshold limit lsb. thermal low limit (all channels) msb 30 c9 r/w read/write thermal low-temperature threshold msb (shared by all channels). thermal low limit (all channels) lsb 31 00 r/w read/write thermal low-temperature threshold lsb (shared by all channels). thermal status, high temperature 32 00 r read the high-temperature thermal status for each channel. thermal status, low temperature 33 00 r read the low-temperature thermal status for each channel. maxim integrated 23 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register map (continued) register 00h: local temperature msb register address (hex) por value (hex) read/ write description therm mask 34 00 r/w mask faults from asserting the therm pin for each channel. temperature channel enable 35 0f r/w read/write temperature channel enable. diode fault status 36 00 r read diode fault status for each channel. local reference temperature msb 40 00 r/w msb of local reference temperature for determining content of the highest temperature registers. local reference temperature lsb 41 00 r/w lsb of local reference temperature for determining content of the highest temperature registers. remote 1 reference temperature msb 42 00 r/w msb of remote channel 1 reference temperature for determining content of the highest temperature registers. remote 1 reference temperature lsb 43 00 r/w lsb of remote channel 1 reference temperature for determining content of the highest temperature registers. remote 2 reference temperature msb 44 00 r/w msb of remote channel 2 reference temperature for determining content of the highest temperature registers. remote 2 reference temperature lsb 45 00 r/w lsb of remote channel 2 reference temperature for determining content of the highest temperature registers. remote 3 reference temperature msb 46 00 r/w msb of remote channel 3 reference temperature for determining content of the highest temperature registers. remote 3 reference temperature lsb 47 00 r/w lsb of remote channel 3 reference temperature for determining content of the highest temperature registers. manufacturer id 50 4d r read manufacturer id. revision code 51 01 r read die revision. factory default value: 00h memory type: sram, volatile memory access r r r r r r r r 00h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 maxim integrated 24 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register 01h: local temperature lsb register 02h: remote 1 temperature msb register 03h: remote 1 temperature lsb register 04h: remote 2 temperature msb factory default value: 00h memory type: sram, volatile memory access r r r r r r r r 01h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r r r r r r r r 02h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r r r r r r r r 03h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r r r r r r r r 04h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 maxim integrated 25 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
highest current temperature value msb. value in the highest temperature register is the greater of all (the temperature channel value minus the channel reference temperature value). register 06h: remote 3 temperature msb register 07h: remote 3 temperature lsb register 10h: highest temperature msb register 05h: remote 2 temperature lsb factory default value: 00h memory type: sram, volatile memory access r r r r r r r r 05h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r r r r r r r r 06h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r r r r r r r r 07h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r r r r r r r r 10h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 maxim integrated 26 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
highest current temperature value lsb. value in the highest temperature register will be the greater of all (the temperature channel value minus the channel reference temperature value). selects which channels are used in determining the contents of the highest temperature register. register 12h: highest temperature enable register 11h: highest temperature lsb factory default value: 00h memory type: sram, volatile memory access r r r r r r r r 11h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: 0fh memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 12h reserved reserved reserved reserved remote 3 remote 2 remote 1 local bit 7 bit 0 bit 7 reserved powers on with a value of 0. bit 6 reserved powers on with a value of 0. bit 5 reserved powers on with a value of 0. bit 4 reserved powers on with a value of 0. bit 3 remote 3 channel 3 highest temperature select bit. 0 = do not use channel 3 in determining the highest temperature. 1 = use channel 3 in determining the highest temperature (default). bit 2 remote 2 channel 2 highest temperature select bit. 0 = do not use channel 2 in determining the highest temperature. 1 = use channel 2 in determining the highest temperature (default). bit 1 remote 1 channel 1 highest temperature select bit. 0 = do not use channel 1 in determining the highest temperature. 1 = use channel 1 in determining the highest temperature (default). bit 0 local local channel highest temperature select bit. 0 = do not use the local channel in determining the highest temperature. 1 = use the local channel in determining the highest temperature (default). maxim integrated 27 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register 13h: confguration register 14h: customer ideality factor factory default value: 10h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 13h stop por timeout interrupt / comparator fault queue fault queue extrange one shot bit 7 bit 0 bit 7 stop standby-mode control bit. setting stop to 1 disables the adc and reduces supply current to 2.5a. 0 = adc enabled (default). 1 = adc disabled. bit 6 por power-on-reset bit. write this bit to logic 1 to enter the power-on state. this bit is self- clearing. power-on default value is 0. bit 5 timeout timeout enable bit. set to logic 0 to enable smbus timeout. 0 = smbus timeout enabled (default). 1 = smbus timeout disabled. bit 4 interrupt/ comparator interrupt/comparator mode-select bit. 0 = interrupt mode. 1 = comparator mode (default). bit 3 fault queue selects the number of consecutive faults needed to assert a thermal fault. 00 = 1 (default) 01 = 2 10 = 4 11 = 6 bit 2 bit 1 extrange extended-range enable bit. 0 = set maximum reportable temperature value to +127.9375oc (default). 1 = set maximum reportable temperature value to +191.9375oc. bit 0 one shot default state is 0. write this bit to a 1 to initiate a single cycle of temperature conversions. all other bits in the confguration register are ignored. after the conversion, the bit automatically resets to 0. one shot can only be enabled within stop mode. factory default value: 18h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 14h d7 d6 d5 d4 d3 d2 d1 d0 see table 8 bit 7 bit 0 maxim integrated 28 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
the temperature offset is calculated using the following equation: -14.875c + b[7:0]/8 = temperature offset the resulting offset range is -14.875c to +17c. with a default power-on value of 77h, the device has a default temperature offset of 0c. register 16h: custom offset register 15h: custom ideality enable factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r/w r/w r/w n/a 15h reserved reserved reserved reserved remote 3 remote 2 remote 1 reserved bit 7 bit 0 bit 7 reserved reserved. bit 6 reserved reserved. bit 5 reserved reserved. bit 4 reserved reserved. bit 3 remote 3 channel 3 remote-diode ideality enable bit. 0 = sets ideality factor to 1.008 (default). 1 = sets the ideality factor to the value from the custom ideality factor register (14h). bit 2 remote 2 channel 2 remote-diode ideality enable bit. 0 = sets ideality factor to 1.008 (default). 1 = sets the ideality factor to the value from the custom ideality factor register (14h). bit 1 remote 1 channel 1 remote-diode ideality enable bit. 0 = sets ideality factor to 1.008 (default). 1 = sets the ideality factor to the value from the custom ideality factor register (14h). bit 0 reserved reserved. factory default value: 77h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 16h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 4 2 3 2 2 2 1 2 0 2 -1 2 -2 2 -3 bit 7 bit 0 maxim integrated 29 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
selects the temperature channels to which the custom offset is applied. the offset value does not affect the value in the highest temperature register. register 17h: custom offset enable factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r/w r/w r/w n/a 17h reserved reserved reserved reserved remote 3 remote 2 remote 1 reserved bit 7 bit 0 bit 7 reserved reserved. bit 6 reserved reserved. bit 5 reserved reserved. bit 4 reserved reserved. bit 3 remote 3 remote channel 3 offset enable bit: 0 = offset not enabled (default). 1 = offset enabled. bit 2 remote 2 remote channel 2 offset enable bit: 0 = offset not enabled (default). 1 = offset enabled. bit 1 remote 1 remote channel 1 offset enable bit: 0 = offset not enabled (default). 1 = offset enabled. bit 0 reserved reserved. maxim integrated 30 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register 18h: filter enable factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r/w r/w r/w n/a 1ch reserved reserved reserved reserved remote 3 remote 2 remote 1 reserved bit 7 bit 0 bit 7 reserved reserved. bit 6 reserved reserved. bit 5 reserved reserved. bit 4 reserved reserved. bit 3 remote 3 channel 3 noise filter select bit. 0 = noise fltering disabled (default). 1 = noise fltering enabled. bit 2 remote 2 channel 2 noise filter select bit. 0 = noise fltering disabled (default). 1 = noise fltering enabled. bit 1 remote 1 channel 1 noise filter select bit. 0 = noise fltering disabled (default). 1 = noise fltering enabled. bit 0 reserved reserved. maxim integrated 31 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register 19h: beta compensation enable register 1ah: beta value channel 1 factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r/w r/w r/w n/a 19h reserved reserved reserved reserved remote 3 remote 2 remote 1 reserved bit 7 bit 0 bit 7 reserved reserved. bit 6 reserved reserved. bit 5 reserved reserved. bit 4 reserved reserved. bit 3 remote 3 channel 3 beta compensation enable bit. 0 = beta compensation disabled (default). 1 = beta compensation enabled. bit 2 remote 2 channel 2 beta compensation enable bit. 0 = beta compensation disabled (default). 1 = beta compensation enabled. bit 1 remote 1 channel 1 beta compensation enable bit. 0 = beta compensation disabled (default). 1 = beta compensation enabled. bit 0 reserved reserved. factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r r r r 1ah reserved reserved reserved reserved beta value beta value beta value beta value bit 7 bit 0 bits [7:4] reserved the bits in these locations are reserved. bits [3:0] beta value reports the amount of beta compensation applied for the remote-diode channel 1 if enabled from the register (see table 12). maxim integrated 32 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. register 1bh: beta value channel 2 register 20h: local thermal high limit msb register 1ch: beta value channel 3 factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r r r r 1bh reserved reserved reserved reserved beta value beta value beta value beta value bit 7 bit 0 bits [7:4] reserved the bits in these locations are reserved. bits [3:0] beta value reports the amount of beta compensation applied for the remote-diode channel 2 if enabled from the beta compensation enable register (see table 12). factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r r r r 1ch reserved reserved reserved reserved beta value beta value beta value beta value bit 7 bit 0 bits [7:4] reserved the bits in these locations are reserved. bits [3:0] beta value reports the amount of beta compensation applied for the remote-diode channel 3 if enabled from the beta compensation enable register (see table 12). factory default value: 7fh memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 20h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 maxim integrated 33 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. register 21h: local thermal high limit lsb register 23h: remote 1 thermal high limit lsb register 22h: remote 1 thermal high limit msb factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 21h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: 7fh memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 22h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 23h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 maxim integrated 34 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. register 25h: remote 2 thermal high limit lsb register 24h: remote 2 thermal high limit msb register 26h: remote 3 thermal high limit msb factory default value: 7fh memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 24h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 25h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: 7fh memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 26h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 maxim integrated 35 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. register 27h: remote 3 thermal high limit lsb register 30h: thermal low limit (all channels) msb register 31h: thermal low limit (all channels) lsb factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 27h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: c9h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 30h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 31h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 maxim integrated 36 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register 32h: thermal status, high temperature factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r r r r 32h reserved reserved reserved reserved remote 3 remote 2 remote 1 local bit 7 bit 0 bits [7:4] reserved reserved. bit 3 remote 3 channel 3 remote-diode high thermal bit. 0 = default value. 1 = indicates that the temperature sensed on the channel 3 remote diode exceeds the selected temperature threshold limit stored in the channel 3 thermal high limit register. bit 2 remote 2 channel 2 remote-diode high thermal bit. 0 = default value. 1 = indicates that the temperature sensed on the channel 2 remote diode exceeds the selected temperature threshold limit stored in the channel 2 thermal high limit register. bit 1 remote 1 channel 1 remote-diode high thermal bit. 0 = default value. 1 = indicates that the temperature sensed on the channel 1 remote diode exceeds the selected temperature threshold limit stored in the channel 1 thermal high limit register. bit 0 local local high thermal bit. 0 = default value. 1 = indicates that the temperature sensed on the local channel exceeds the selected temperature threshold limit stored in the local thermal high limit register. maxim integrated 37 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register 33h: thermal status, low temperature factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r r r r 33h reserved reserved reserved reserved remote 3 remote 2 remote 1 local bit 7 bit 0 bits [7:4] reserved reserved. bit 3 remote 3 channel 3 remote-diode low thermal bit. 0 = default value. 1 = indicates that the temperature sensed on the channel 3 remote diode is less than the selected temperature threshold limit stored in the thermal low limit register. bit 2 remote 2 channel 2 remote-diode low thermal bit. 0 = default value. 1 = indicates that the temperature sensed on the channel 2 remote diode is less than the selected temperature threshold limit stored in the thermal low limit register. bit 1 remote 1 channel 1 remote-diode low thermal bit. 0 = default value. 1 = indicates that the temperature sensed on the channel 1 remote diode is less than the selected temperature threshold limit stored in the thermal low limit register. bit 0 local local low thermal bit. 0 = default value. 1 = indicates that the temperature sensed on the local channel is less than the selected temperature threshold limit stored in the thermal low limit register. maxim integrated 38 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register 34h: therm mask factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r/w r/w r/w r/w 34h reserved reserved reserved reserved remote 3 remote 2 remote 1 local bit 7 bit 0 bits [7:4] reserved reserved. bit 3 remote 3 channel 3 thermal mask bit. 0 = default value. 1 = masks the assertion of the trm pin when a thermal fault on channel 3 occurs. bit 2 remote 2 channel 2 thermal mask bit. 0 = default value. 1 = masks the assertion of the trm pin when a thermal fault on channel 2 occurs. bit 1 remote 1 channel 1 thermal mask bit. 0 = default value. 1 = masks the assertion of the trm pin when a thermal fault on channel 1 occurs. bit 0 local local thermal mask bit. 0 = default value. 1 = masks the assertion of the trm pin when a thermal fault on the local channel occurs. maxim integrated 39 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
register 35h: temperature channel enable factory default value: 0fh memory type: sram, volatile memory access n/a n/a n/a n/a r/w r/w r/w r/w 35h reserved reserved reserved reserved enable 3 enable 2 enable 1 enable local bit 7 bit 0 bits [7:4] reserved reserved. bit 3 remote 3 channel 3 enable bit. 0 = channel 3 is not enabled and is skipped during the temperature conversion cycle. diode fault detection is not performed on this channel. 1 = temperature conversions and diode fault detection are enabled for channel 3 (default). bit 2 remote 2 channel 2 enable bit. 0 = channel 2 is not enabled is skipped during the temperature conversion cycle. diode fault detection is not performed on this channel. 1 = temperature conversions and diode fault detection are enabled for channel 2 (default). bit 1 remote 1 channel 1 enable bit. 0 = channel 1 is not enabled, and is skipped during the temperature conversion cycle. diode fault detection is not performed on this channel. 1 = temperature conversions and diode fault detection are enabled for channel 1 (default). bit 0 local local enable bit. 0 = the local channel is not enabled, and will be skipped during the temperature conversion cycle. 1 = temperature conversions are enabled for the local channel (default). maxim integrated 40 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
msb of the local reference temperature (used for determining the content of the highest temperature registers). when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. register 36h: diode fault status register 40h: local reference temperature msb factory default value: 00h memory type: sram, volatile memory access n/a n/a n/a n/a r/w r/w r/w n/a 36h reserved reserved reserved reserved remote 3 remote 2 remote 1 reserved bit 7 bit 0 bits [7:4] reserved reserved. bit 3 remote 3 channel 3 diode fault bit. 0 = default value. 1 = indicates an open or short on the channel 3 remote-diode connection. bit 2 remote 2 channel 2 diode fault bit. 0 = default value. 1 = indicates an open or short on the channel 2 remote-diode connection. bit 1 remote 1 channel 1 diode fault bit. 0 = default value. 1 = indicates an open or short on the channel 1 remote-diode connection. bit 0 reserved reserved. always 0. factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 40h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 maxim integrated 41 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
msb of the channel 1 reference temperature (used for determining the content of the highest temperature registers). when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. lsb of the channel 1 reference temperature (used for determining the content of the highest temperature registers). when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. lsb of the local reference temperature (used for determining the content of the highest temperature registers). when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. register 41h: local reference temperature lsb register 43h: remote 1 reference temperature lsb register 42h: remote 1 reference temperature msb factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 41h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 42h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 43h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 maxim integrated 42 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
lsb of the channel 2 reference temperature (used for determining the content of the highest temperature registers). when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. msb of the channel 2 reference temperature (used for determining the content of the highest temperature registers). when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. msb of the channel 3 reference temperature (used for determining the content of the highest temperature registers). when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. register 46h: remote 3 reference temperature msb register 44h: remote 2 reference temperature msb register 45h: remote 2 reference temperature lsb factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 44h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 45h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 46h d15 d14 d13 d12 d11 d10 d9 d8 oc sign 2 6 2 5 2 4 2 3 2 2 2 1 2 0 bit 7 bit 0 maxim integrated 43 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
lsb of the channel 3 reference temperature (used for determining the content of the highest temperature registers). when the extended format is selected, all limit and reference temperature registers must be written in this format. they are not automatically translated by toggling the extended format bit. contains the code for the manufacturers id for the device. contains the revision code for the device. register 47h: remote 3 reference temperature lsb register 51h: revision code register 50h: manufacturer id factory default value: 00h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 47h d7 d6 d5 d4 d3 d2 d1 d0 oc 2 -1 2 -2 2 -3 2 -4 0 0 0 0 bit 7 bit 0 factory default value: 4dh memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 50h d7 d6 d5 d4 d3 d2 d1 d0 0 1 0 0 1 1 0 1 bit 7 bit 0 factory default value: 01h memory type: sram, volatile memory access r/w r/w r/w r/w r/w r/w r/w r/w 51h d7 d6 d5 d4 d3 d2 d1 d0 0 0 0 0 0 0 0 0 bit 7 bit 0 maxim integrated 44 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
applications information remote-diode selection the device directly measures the die temperature of cpus and other ics that have on-chip temperature-sensing diodes (see the typical application circui t s ), or it can measure the temperature of a discrete diode-connected transistor. discrete remote diodes when the remote-sensing diode is a discrete transistor, its collector and base must be connected together; pnp or npn discrete transistors can be used. table 16 lists examples of discrete transistors that are appropriate for use with this device. the transistor must be a small-signal type with a relatively 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 10a; at the lowest expected tem - perature, the forward voltage must be less than 0.95v at 100a. large power transistors must not be used. also, ensure that the base resistance is less than 100. tight specifications for forward-current gain (e.g., 50 < < 150) indicate that the manufacturer has good process controls and that the devices have consistent v be characteristics. manufacturers of discrete transistors do not normally specify or guarantee ideality factor. this normally is not a problem since good-quality discrete transistors tend to have ideality factors that fall within a relatively narrow range. variations in remote temperature readings of less than 2c with a variety of discrete transistors have been observed. however, it is good design practice to verify good consistency of temperature readings with several discrete transistors from any supplier under consideration. unused diode channels if one or more of the remote-diode channels is not needed, disconnect the dxp_ and dxn_ inputs for that channel, or connect the dxp_ to the corresponding dxn_. 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 therm mask register. this pre - vents unused channels from causing therm to assert. thermal mass and self-heating when sensing local temperature, the device measures the temperature of the 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 comparison, making air-temperature measure - ments impractical. since the thermal mass of the pcb is far greater than that of the device, the device follows temperature changes on the pcb with little or no perceiv - able 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 conversion 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 sig - nificantly affect measurement accuracy. remote-sensor self-heating due to the diode current source is negligible. table 16. remote sensors transistor suppliers supplier pnp model number central semiconductor corp. (usa) cmpt3906 2n3906 fairchild semiconductor (usa) mmbt3906 2n3906 infneon (germany) smbt3906 on semiconductor (usa) mmbt3906 2n3906 rohm semiconductor (usa) sst3906 samsung (korea) kst3906-tf siemens (germany) smbt3906 zetex (england) fmmt3906ct-nd maxim integrated 45 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
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 100pf capacitor between dxp_ and dxn_. larger capacitor values can be used for added filtering; however, this can introduce errors due to the rise time of the switched current source. noise can be minimized with careful pcb layout, as discussed in the pcb layout section. slave address slave addresses can be selected by connecting add, as shown in table 17 . pcb layout follow the guidelines below to reduce the measurement error when measuring remote temperature: 1) place the device as close as possible to the thermal diode. in noisy environments, such as a computer motherboard, this distance is typically 10cm to 20cm. this length can be increased if the worst noise sources are avoided. noise sources include displays, clock generators, memory buses, and pci buses. 2) do not route the dxp_ and dxn_ traces across fast digital signals, which can easily introduce +30c 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 trac - es should go to a thermal diode. route these traces away from any higher voltage traces, such as +12v dc . leakage currents from pcb contamination must be dealt with carefully since a 20m leakage path from dxp_ to ground causes approximately +1c 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. use wide traces when possible (5-mil to 10-mil traces are typical). twisted-pair and shielded cables use a twisted-pair cable to connect the remote sensor for remote-sensor distances longer than 20cm or in very noisy environments. twisted-pair cable lengths can be between 2m and 4m before noise introduces excessive errors. for longer distances, the best solution is a shielded twisted pair, such as those used for audio microphones. for example, belden no. 8451 works well for distances up to 100ft in a noisy environment. at the device, connect the twisted-pair cables to dxp_ and dxn_ and the shielded cable to gnd. leave the shielded cable unconnected at the remote sensor. for very long cable runs, the cables parasitic capacitance often provides noise filtering; therefore, the 100pf capacitor can often be removed, or reduced in value. table 17. slave address selection note: resistor value tolerence must be 5% of the listed values. figure 5. recommended dxp_ - dxn_ pcb traces (the two outer-guard traces are recommended if high-voltage traces are near the dxn_ and dxp_ traces) resistor between add and gnd slave address (hex) 15k? to 39k? 0x9e 9.31k? 0x9c 6.81k 0x9a 4.75k 0x98 3.01k 0x3e 1.69k 0x3c 750 0x3a 0 (< 250? ) 0x38 5?10 mils 5?10 mils 5?10 mils minimum 5?10 mils gnd dxp_ dxn_ gnd maxim integrated 46 MAX31730 3-channel remote temperature sensor www.maximintegrated.com
+denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. *future productco ntact factory for availability. **ep = exposed pad. package type package code outline no. land pattern no. 10 max u10+2 21-0061 90-033 0 12 tdfn-ep td1233+1c 21-0664 90-0 397 part temp range pin-package MAX31730aub+ -40c to +125c 10 max MAX31730aub+t -40c to +125c 10 max MAX31730atc+* -40c to +125c 12 tdfn-ep** MAX31730atc+t* -40c to +125c 12 tdfn-ep** maxim integrated 47 package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. chip information process: cmos ordering information MAX31730 3-channel remote temperature sensor www.maximintegrated.com
revision number revision date description pages changed 0 3/14 initial release ? 2014 maxim integrated products, inc. 48 revision history maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integrated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and specifcations without notice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. MAX31730 3-channel remote temperature sensor for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim integrateds website at www.maximintegrated.com.

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