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digital temperature sensor with sst interface adt7484a/ADT7486A rev. 0 information furnished by analog devices is believed to be accurate and reliable. however, no responsibility is assumed by analog devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. specifications subject to change without notice. no license is granted by implication or otherwise under any patent or patent rights of analog devices. trademarks and registered trademarks are the property of their respective owners. one technology way, p.o. box 9106, norwood, ma 02062-9106, u.s.a. tel: 781.329.4700 www.analog.com fax: 781.461.3113 ?2006 analog devices, inc. all rights reserved. features 1 on-chip temperature sensor 1 or 2 remote temperature sensors simple serial transport? (sst?) interface rev 1 compliant applications personal computers portable personal devices industrial sensor nets general description the adt7484a/ADT7486A are simple digital temperature sensors for use in pc applications with a simple serial transport (sst) interface. these devices can monitor their own temperature as well as the temperature of one (adt7484a) or two (ADT7486A) remote sensor diodes. the adt7484a/ADT7486A are controlled by a single sst bidirectional data line. the devices are fixed- address sst clients where the target address is chosen by the state of the two address pins, add0 and add1. functional block diagram sst interface analog mux (ADT7486A only) offset registers address selection digital mux local temperature value register remote temperature value register a/d converter on-chip temperature sensor d1+ d2? v dd gnd reserved adt7484a/ ADT7486A sst add1 add0 d1? d2+ 05198-001 figure 1.
adt7484a/ADT7486A rev. 0 | page 2 of 16 table of contents features .............................................................................................. 1 applications ....................................................................................... 1 general description ......................................................................... 1 functional block diagram .............................................................. 1 revision history ............................................................................... 2 specifications ..................................................................................... 3 absolute maximum ratings ............................................................ 5 thermal resistance ...................................................................... 5 esd caution .................................................................................. 5 pin configurations and functional descriptions ........................ 6 typical performance characteristics ............................................. 7 product description ......................................................................... 9 sst interface ..................................................................................9 temperature measurement ........................................................... 12 temperature measurement method ........................................ 12 reading temperature measurements ...................................... 12 sst temperature sensor data format .................................... 13 using discrete transistors ........................................................ 13 layout considerations ............................................................... 13 temperature offset .................................................................... 14 application schematics ............................................................. 14 outline dimensions ....................................................................... 15 ordering guide .......................................................................... 15 revision history 7/06revision 0: initial version
adt7484a/ADT7486A rev. 0 | page 3 of 16 specifications t a = t min to t max , v cc = v min to v max , unless otherwise noted. table 1. parameter min typ max unit test conditions/comments power supply supply voltage, v cc 3.0 3.3 3.6 v undervoltage lockout threshold 2.8 v average operating supply current, i dd 3.8 5 ma continuous conversions temperature-to-digital converter local sensor accuracy +1 1.75 c 40c t a 70c, v cc = 3.3 v 5% 4 c ?40c t a +100c remote sensor accuracy 1 c ?40c t d +125c; t a = 25c; v cc = 3.3 v +1 1.75 c ?40c t d +125c; ?40 t a 70c, v cc = 3.3 v 5% 4 c ?40c t d +125c; ?40 t a +100c remote sensor source current 12 a low level 80 a mid level 204 a high level resolution 0.016 c series resistance cancellation 1.5 k the adt7484a and ADT7486A cancel 1.5 k in series with the remote thermal diode conversion time (local temperature) 1 12 ms averaging enabled conversion time (remote temperature) 1 38 ms averaging enabled total monitoring cycle time 1 50 ms averaging enabled digital inputs (add0, add1) input high voltage, v ih 2.3 v input low voltage, v il 0.8 v input high current, i ih ?1 a v in = v cc input low current, i il 1 a v in = 0 pin capacitance 5 pf digital i/o (sst pin) input high voltage, v ih 1.1 v input low voltage, v il 0.4 v hysteresis 1 150 mv between input switching levels output high voltage, v oh 1.1 1.9 v i source = 6 ma (maximum) high impedance state leakage, i leak 1 a device powered on sst bus; v sst = 1.1 v, v cc = 3.3 v high impedance state leakage, i leak 10 a device unpowered on sst bus; v sst = 1.1 v, v cc = 0 v signal noise immunity, v noise 300 mv p-p noise glitches from 10 mhz to 100 mhz; width up to 50 ns sst timing bitwise period, t bit 0.495 500 s high level time for logic 1, t h1 2 0.6 t bit 0.75 t bit 0.8 t bit s t bit defined in speed negotiation high level time for logic 0, t h0 2 0.2 t bit 0.25 t bit 0.4 t bit s time to assert sst high for logic 1, t su, high 0.2 t bit s hold time, t hold 3 0.5 t bit-m s see sst specification rev 1.0 stop time, t stop 1.25 t bit 2 t bit 2 t bit s device responding to a constant low level driven by originator
adt7484a/ADT7486A rev. 0 | page 4 of 16 parameter min typ max unit test conditions/comments time to respond after a reset, t reset 0.4 ms response time to speed negotiation after power-up 500 s time after power-up when device can participate in speed negotiation 1 guaranteed by design, not production tested. 2 minimum and maximum bit t imes are relative to t bit defined in the timin g negotiation pulse. 3 devices compatible with hold time spec ification as driven by sst originator.
adt7484a/ADT7486A rev. 0 | page 5 of 16 absolute maximum ratings table 2. parameter rating supply voltage (v cc ) 3.6 v voltage on any other pin (including sst pin) 3.6 v input current at any pin 5 ma package input current 20 ma maximum junction temperature (t j max) 150c storage temperature range ?65c to +150c lead temperature, soldering ir peak reflow temperature 260c lead temperature (10 sec) 300c esd rating 1500 v stresses above those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. thermal resistance ja is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. table 3. thermal resistance package type ja jc unit 8-lead msop (adt7484a) 206 44 c/w 10-lead msop (ADT7486A) 206 44 c/w esd caution esd (electrostatic discharge) sensitive device. electros tatic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge wi thout detection. although this product features proprietary esd protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. therefore, proper esd precautions are recommended to avoid performance degradation or loss of functionality.
adt7484a/ADT7486A rev. 0 | page 6 of 16 pin configurations and functional descriptions v cc 1 gnd 2 d1+ 3 d1? 4 sst 8 add0 7 reserved 6 add1 5 adt7484a top view (not to scale) 0 5198-002 v cc 1 gnd 2 d1+ 3 d1? 4 d2+ 5 sst 10 add0 9 reserved 8 add1 7 d2? 6 ADT7486A top view (not to scale) 05198-003 figure 2. adt7484a 8-lead msop figure 3. ADT7486A 10-lead msop table 4. adt7484a pin function descriptions pin o. mnemonic type description 1 v cc power supply 3.3 v 10%. 2 gnd ground ground pin. 3 d1+ analog input positive connection to remote temperature sensor. 4 d1? analog input negative connection to remote temperature sensor. 5 add1 digital input sst address select. 6 reserved reserved connect to ground. 7 add0 digital input sst address select. 8 sst digital input/output sst bidirectional data line. table 5. ADT7486A pin function descriptions pin o. mnemonic type description 1 v cc power supply 3.3 v 10%. 2 gnd ground ground pin. 3 d1+ analog input positive connection to remote 1 temperature sensor. 4 d1? analog input negative connection to remote 1 temperature sensor. 5 d2+ analog input positive connection to remote 2 temperature sensor. 6 d2? analog input negative connection to remote 2 temperature sensor. 7 add1 analog input sst address select. 8 reserved analog input connect to ground. 9 add0 digital input sst address select. 10 sst digital input/output sst bidirectional data line.
adt7484a/ADT7486A rev. 0 | page 7 of 16 typical performance characteristics 1.55 1.20 2.6 v cc (v) sst o/p (v) 1.50 1.45 1.40 1.35 1.30 1.25 2.8 3.0 3.2 3.4 3.6 750 ? (~2ma) 270 ? (~5.2ma) 120 ? (~10.6ma) 05198-009 figure 4. sst o/p level vs. supply voltage ?45 temperature (c) i dd (ma) ?25?51535557595115 dev3 dev2 dev1 3.45 3.46 3.47 3.48 3.49 3.50 3.51 3.52 3.53 3.54 3.55 3.56 05198-010 figure 5. supply current vs. temperature 7 ?1 ?60 140 temperature (c) temperature error (c) 05198-018 6 5 4 3 2 1 0 ?40 ?20 0 20 40 60 80 100 120 lo spec (v cc =3.6v) mean (v cc =3.3v) hi spec (v cc =3v) figure 6. local temperature error 1.55 1.20 ?50 150 temperature (c) sst o/p (v) 1.50 1.45 1.40 1.35 1.30 1.25 05 01 0 0 120 ? (~10.6ma) 270 ? (~5.2ma) 750 ? (~2ma) 05198-011 figure 7. sst o/p level vs. temperature 3.9 2.65 3.65 v cc (v) i dd (ma) 3.7 3.5 3.3 3.1 2.9 2.85 3.05 3.25 3.45 dev1 dev3 dev2 05198-012 figure 8. supply current vs. voltage 7 ?2 ?60 140 temperature (c) temperature error (c) 05198-019 ?40 ?20 0 20 40 60 80 100 120 6 5 4 3 2 1 0 ?1 hi spec (v cc =3v) lo spec (v cc =3.6v) mean (v cc =3.3v) figure 9. remote temperature error
adt7484a/ADT7486A rev. 0 | page 8 of 16 15 ?40 0 100 resistance (m ? ) error (c) 05198-020 10 5 0 ?5 ?10 ?15 ?20 ?25 ?30 ?35 20 40 60 80 d+ to gnd dev2_ext2 dev3_ext1 dev3_ext2 dev1_ext1 dev1_ext2 dev2_ext1 dev1_ext1 dev1_ext2 dev2_ext1 dev2_ext2 dev3_ext1 dev3_ext2 d+ to v cc figure 10. remote temperature error vs. pcb resistance 30 ?5 10k 1g noise frequency (c) temperature error (c) 25 20 15 10 5 0 100k 1m 10m 100m 40mv 60mv 100mv 05198-013 figure 11. temperature error vs. common-mode noise frequency 20 ?10 10k 1g power supply noise frequency (hz) temperature error (c) 15 10 5 0 ?5 100k 1m 10m 100m 125mv 50mv 05198-014 figure 12. local temperature error vs. power supply noise 0 ?90 05 capacitance (nf) error (c) 0 ?10 ?20 ?30 ?40 ?50 ?60 ?70 ?80 10 20 30 40 ext1 ext2 05198-015 figure 13. remote temperature error vs. capacitance between d1+ and d1? 7 0 10k 1g noise frequency (c) temperature error (c) 100k 1m 10m 100m 6 5 4 3 2 1 10mv 40mv 20mv 05198-016 figure 14. temperature error vs. differential-mode noise frequency 5 ?3 10k 1g power supply noise frequency (hz) temperature error (c) 100k 1m 10m 100m 125mv 50mv 4 3 2 1 0 ?1 ?2 05198-017 figure 15. remote temperature error vs. power supply noise
adt7484a/ADT7486A rev. 0 | page 9 of 16 product description the adt7484a is a single remote temperature sensor, and the ADT7486A is a dual temperature sensor for use in pc applications. the adt7484a/ADT7486A accurately measure local and remote temperature and communicate over a one-wire simple serial transport (sst) bus interface. sst interface simple serial transport (sst) is a one-wire serial bus and a communications protocol between components intended for use in personal computers, personal handheld devices, or other industrial sensor nets. the adt7484a/ADT7486A support sst specification rev 1. sst is a licensable bus technology from analog devices, inc., and intel corporation. to inquire about obtaining a copy of the simple serial transport specification or an sst technology license, please email analog devices, at sst_licensing@analog.com or write to analog devices, 3550 north first street, san jose, ca 95134, attention: sst licensing, m/s b7-24. adt7484a/ADT7486A client address the client address for the ad t7484a/ADT7486A is selected using the address pin. the address pin is connected to a float detection circuit, which allows the adt7484a/ADT7486A to distinguish between three input states: high, low (gnd), and floating. the address range for fixed address, discoverable devices is 0x48 to 0x50. table 6. adt7484a/ADT7486A selectable addresses add1 add0 address selected low (gnd) low (gnd) 0x48 low (gnd) float 0x49 low (gnd) high 0x4a float low (gnd) 0x4b float float 0x4c float high 0x4d high low (gnd) 0x4e high float 0x4f high high 0x50
adt7484a/ADT7486A rev. 0 | page 10 of 16 command summary table 7 summarizes the commands supported by the adt7484a/ADT7486A de vices when directed at the target address selected by the fixed address pins. it contains the command name, command code (cc), write data length (wl), read data length (rl), and a brief description. table 7. command code summary command command code cc rite ength read ength r description ping() 0x00 0x00 0x00 shows a nonzero fcs over the header if present. getinttemp() 0x00 0x01 0x02 shows the temperature of the devices internal thermal diode. getext1temp() 0x01 0x01 0x02 shows the temp erature of external thermal diode 1. getext2temp() 0x02 0x01 0x02 shows the temperature of external thermal diode 2 (ADT7486A only). getalltemps() 0x00 0x01 0x04 (adt7484a) 0x06 (ADT7486A) shows a 4- or 6-byte block of data (adt7484a: getinttemp, getext1temp; ADT7486A: getinttemp, getext1temp, getext2temp). setext1offset() 0xe0 0x03 0x00 sets the offset used to correct errors in external diode 1. getext1offset() 0xe0 0x01 0x02 shows the offset that the d evice is using to correct errors in external diode 1. setext2offset() 0xe1 0x03 0x00 sets the offset used to correct errors in external diode 2 (ADT7486A only). getext2offset() 0xe1 0x01 0x02 shows the offset that the d evice is using to correct errors in external diode 2 (ADT7486A only). resetdevice() 0xf6 0x01 0x00 functional reset. the adt7484a/ADT7486A also respond to this command when directed to the target address 0x00. getdib() 0xf7 0xf7 0x01 0x01 0x08 0x10 shows information used by sw to identify the devices capabilities. can be in 8- or 16-byte format.
adt7484a/ADT7486A rev. 0 | page 11 of 16 command code details adt7484a/ADT7486A device identifier block the getdib() command retrieves the device identifier block (dib), which provides information to identify the capabilities of the adt7484a/ADT7486A. the data re turned can be in 8- or 16-byte format. the full 16 bytes of dib is detailed in table 8 . the 8-byte format involves the first eight bytes described in this table. byte-sized data is returned in the respective fields as it appears in table 8 . word-sized data, including vendor id, device id, and data values use little endian format, that is, the lsb is returned first, followed by the msb. table 8. dib byte details byte ame value description 0 device capabilities 0xc0 fixed address device 1 version/revision 0x10 meets version 1 of the sst specification 2, 3 vendor id 00x11d4 contains company id number in little endian format 4, 5 device id 0x7484 or 0x7486 contains device id number in little endian format 6 device interface 0x01 sst device 7 function interface 0x00 reserved 8 reserved 0x00 reserved 9 reserved 0x00 reserved 10 reserved 0x00 reserved 11 reserved 0x00 reserved 12 reserved 0x00 reserved 13 reserved 0x00 reserved 14 revision id 0x05 contains revision id 15 client device address 0x48 to 0x50 dependent on the state of the address pins ping() the ping() command verifies if a device is responding at a particular address. the adt7484a/ADT7486A show a valid nonzero fcs in response to the ping() command when correctly addressed. table 9. ping() command target address rite ength read ength fcs device address 0x00 0x00 resetdevice() this command resets the register map and conversion controller. the reset command can be global or directed at the client address of the adt7484a/ADT7486A. table 10. resetdevice() command target address rite ength read ength reset command fcs device address 0x01 0x00 0xf6 getinttemp() the adt7484a/ADT7486A show the local temperature of the device in response to the getinttemp() command. the data has a little endian, 16-bit, twos complement format. getexttemp() prompted by the getexttemp() command, the adt7484a/ ADT7486A show the temperature of the remote diode in little endian, 16-bit, twos complement format. the adt7484a/ ADT7486A show 0x8000 in response to this command if the external diode is an open or short circuit. getalltemps() the adt7484a shows the local and remote temperatures in a 4-byte block of data (internal temperature first, followed by external temperature 1) in response to a getalltemps() command. the ADT7486A shows the local and remote tem- peratures in a 6-byte block of data (internal temperature first, followed by external temperature 1 and external temperature 2) in response to this command. setextoffset() this command sets the offset that the adt7484a/ADT7486A will use to correct errors in the external diode. the offset is set in little endian, 16-bit, twos complement format. the maximum offset is 128c with +0.25c resolution. getextoffset() this command causes the adt7484a/ADT7486A to show the offset that they are using to correct errors in the external diode. the offset value is returned in little endian format, that is, lsb before msb. adt7484a/ADT7486A response to unsupported commands a full list of command codes supported by the adt7484a/ ADT7486A is given in table 7 . the offset registers (command codes 0xe0 and 0xe1) are the only registers that the user can write to. the other defined registers are read only. writing to register addresses 0x03 to 0xdf shows a valid fsc, but no action is taken by the adt7484a/ADT7486A. the adt7484a/ADT7486A show an invalid fsc if the user attempts to write to the devices between command codes 0xe2 to 0xee and no data is written to the device. these registers are reserved for the manufacturers use only, and no data can be written to the device via these addresses.
adt7484a/ADT7486A rev. 0 | page 12 of 16 temperature measurement the adt7484a/ADT7486A each have two dedicated temperature measurement channels: one for measuring the temperature of an on-chip band gap temperature sensor, and one for measuring the temperature of a remote diode, usually located in the cpu or gpu. the adt7484a monitors one local and one remote temperature channel, whereas the ADT7486A monitors one local and two remote temperature channels. monitoring of each of the channels is done in a round-robin sequence. the monitoring sequence is in the order shown in table 11 . table 11. temperature monitoring sequence channel number measurement conversion time (ms) 0 local temperature 12 1 remote temperature 1 38 2 remote temperature 2 (ADT7486A only) 38 temperature measurement method a simple method for measuring temperature is to exploit the negative temperature coefficient of a diode by measuring the base-emitter voltage (v be ) of a transistor operated at constant current. unfortunately, this technique requires calibration to null the effect of the absolute value of v be , which varies from device to device. the technique used in the adt7484a/ADT7486A measures the change in v be when the device is operated at three different currents. figure 16 shows the input signal conditioning used to measure the output of a remote temperature sensor. this figure shows the remote sensor as a substrate transistor, which is provided for temperature monitoring on some microprocessors, but it could also be a discrete transistor. if a discrete transistor is used, the collector is not grounded and should be linked to the base. to prevent ground noise from interfering with the measurement, the more negative terminal of the sensor is not referenced to ground, but is biased above ground by an internal diode at the d1? input. if the sensor is operating in an extremely noisy environment, c1 can be added as a noise filter. its value should not exceed 1000 pf. to me asure v be , the operating current through the sensor is switched between three related currents. figure 16 shows n1 i and n2 i as different multiples of the current i. the currents through the temperature diode are switched between i and n1 i, giving v be1 , and then between i and n2 i, giving v be2 . the temperature can then be calculated using the two v be measurements. this method can also cancel the effect of series resistance on the temperature measurement. the resulting v be waveforms are passed through a 65 khz low-pass filter to remove noise and then through a chopper-stabilized amplifier to amplify and rectify the waveform, producing a dc voltage proportional to v be . the adc digitizes this voltage, and a temperature measurement is produced. to reduce the effects of noise, digital filtering is performed by averaging the results of 16 measurement cycles for low conversion rates. signal conditioning and measurement of the internal temperature sensor is performed in the same manner. c1* d+ bias diode *capacitor c1 is optional. it should only be used in noisy environments. v dd to adc v out+ v out? remote sensing transistor d? i n1 i n2 i i bias low-pass filter f c =65khz 05198-004 figure 16. signal conditioning for remote diode temperature sensors reading temperature measurements the temperature measurement command codes are detailed in table 12 . the temperature data returned is two bytes in little endian format, that is, lsb before msb. all temperatures can be read together by using command code 0x00 with a read length of 0x04. the command codes and returned data are described in table 12 . table 12. temperature channel command codes temp channel command code returned data internal 0x00 lsb, msb external 1 0x01 lsb, msb external 2 0x02 lsb, msb all temps 0x00 internal lsb, internal msb; external 1 lsb, external 1 msb; external 2 lsb, external 2 msb
adt7484a/ADT7486A rev. 0 | page 13 of 16 sst temperature sensor data format the data for temperature is structured to allow values in the range of 512c to be reported. thus, the temperature sensor format uses a twos complement, 16-bit binary value to represent values in this range. this format allows temperatures to be represented with approximately a 0.016c resolution. table 13. sst temperature data format twos complement temperature (c) msb lsb ?125 1110 0000 1100 0000 ?80 1110 1100 0000 0000 ?40 1111 0110 0000 0000 ?20 1111 1011 0011 1110 ?5 1111 1110 1100 0000 ?1 1111 1111 1100 0000 0 0000 0000 0000 0000 +1 0000 0000 0100 0000 +5 0000 0001 0100 0000 +20 0000 0100 1100 0010 +40 0000 1010 0000 0000 +80 0001 0100 0000 0000 +125 0001 1111 0100 0000 using discrete transistors if a discrete transistor is used, the collector is not grounded and should be linked to the base. if a pnp transistor is used, the base is connected to the d1? input and the emitter is connected to the d1+ input. if an npn transistor is used, the emitter is connected to the d1? input and the base is connected to the d1+ input. figure 17 shows how to connect the adt7484a/ADT7486A to an npn or pnp transistor for temperature measurement. to prevent ground noise from interfering with the measurement, the more negative terminal of the sensor is not referenced to ground, but is biased above ground by an internal diode at the d1? input. d+ d? adt7484a/ ADT7486A 2n3904 npn d+ d? adt7484a/ ADT7486A 2n3906 pnp 05198-005 figure 17. connections for npn and pnp transistors the adt7484a/ADT7486A show an external temperature value of 0x8000 if the external diode is an open or short circuit. layout considerations digital boards can be electrically noisy environments. take the following precautions to protect the analog inputs from noise, particularly when measuring the very small voltages from a remote diode sensor: ? place the device as close as possible to the remote sensing diode. provided that the worst noise sources, such as clock generators, data/address buses, and crts, are avoided, this distance can be four to eight inches. ? route the d1+ and d1? tracks close together in parallel with grounded guard tracks on each side. provide a ground plane under the tracks if possible. ? use wide tracks to minimize inductance and reduce noise pickup. a 5 mil track minimum width and spacing is recommended. 5mil 5mil 5mil 5mil 5mil 5mil 5mil gnd d+ gnd d? 0 5198-006 figure 18. arrangements of signal tracks ? try to minimize the number of copper/solder joints, which can cause thermocouple effects. where copper/solder joints are used, make sure that they are in both the d1+ and d1? paths and are at the same temperature. ? thermocouple effects should not be a major problem because 1c corresponds to about 240 v, and thermocouple voltages are about 3 v/c of the temperature difference. unless there are two thermocouples with a big temperature differential between them, thermocouple voltages should be much less than 200 mv. ? place a 0.1 f bypass capacitor close to the device. ? if the distance to the remote sensor is more than eight inches, the use of a twisted-pair cable is recommended. this works for distances of about 6 to 12 feet. ? for very long distances (up to 100 feet), use shielded twisted- pair cables, such as belden #8451 microphone cables. connect the twisted-pair cable to d1+ and d1? and the shield to gnd, close to the device. leave the remote end of the shield unconnected to avoid ground loops. because the measurement technique uses switched current sources, excessive cable and/or filter capacitance can affect the measurement. when using long cables, the filter capacitor can be reduced or removed. cable resistance can also introduce errors. a 1 series resistance introduces about 0.5c error.
adt7484a/ADT7486A rev. 0 | page 14 of 16 temperature offset as cpus run faster, it is more difficult to avoid high frequency clocks when routing the d1+ and d1? tracks around a system board. even when the recommended layout guidelines are followed, there may still be temperature errors, attributed to noise being coupled on to the d1+ and d1? lines. high frequency noise generally has the effect of producing temperature mea- surements that are consistently too high by a specific amount. the adt7484a/ADT7486A have a temperature offset command code of 0xe0 through which a desired offset can be set. by doing a one-time calibration of the system, the offset caused by system board noise can be calculated and nulled by specifying it in the adt7484a/ADT7486A. the offset is automatically added to every temperature measurement. the maximum offset is 128c with 0.25c resolution. the offset format is the same as the temperature data format16-bit, twos complement notation, as shown in table 13 . the offset should be programmed in little endian format, that is, lsb before msb. the offset value is also returned in little endian format when read. application schematics v cc v cc 1 gnd 2 d1+ 3 d1? 4 sst 8 add0 7 reserved 6 add1 5 adt7484a 2n3904 or cpu thermal diode 05198-007 sst figure 19. adt7484a typical application schematic v cc 1 2 3 4 v cc gnd d1+ d1? d2+ 5 10 9 8 7 sst add0 reserved add1 d2? 6 ADT7486A cpu thermal diode 2 n3904 npn sst 05198-008 figure 20. ADT7486A typical application schematic
adt7484a/ADT7486A rev. 0 | page 15 of 16 outline dimensions compliant to jedec standards mo-187-aa 0.80 0.60 0.40 8 0 4 8 1 5 pin 1 0.65 bsc seating plane 0.38 0.22 1.10 max 3.20 3.00 2.80 coplanarity 0.10 0.23 0.08 3.20 3.00 2.80 5.15 4.90 4.65 0.15 0.00 0.95 0.85 0.75 figure 21. 8-lead mini small outline package [msop] (rm-8) dimensions shown in millimeters compliant to jedec standards mo-187-ba 0.23 0.08 0.80 0.60 0.40 8 0 0.15 0.05 0.33 0.17 0.95 0.85 0.75 seating plane 1.10 max 10 6 5 1 0.50 bsc pin 1 coplanarity 0.10 3.10 3.00 2.90 3.10 3.00 2.90 5.15 4.90 4.65 figure 22. 10-lead mini small outline package [msop] (rm-10) dimensions shown in millimeters ordering guide model temperature range package description package option branding adt7484aarmz-reel 1 C40c to +125c 8-lead msop rm-8 t20 adt7484aarmz-reel7 1 C40c to +125c 8-lead msop rm-8 t20 ADT7486Aarmz-reel 1 C40c to +125c 10-lead msop rm-10 t22 ADT7486Aarmz-reel7 1 C40c to +125c 10-lead msop rm-10 t22 1 z = pb-free part.
adt7484a/ADT7486A rev. 0 | page 16 of 16 notes ?2006 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. d05198-0-7/06(0)

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