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a adm1021a rev. d 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. 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: 781/326-8703 ? 2004 analog devices, inc. all rights reserved. functional block diagram on-chip temp. sensor analog mux a-to-d converter local temperature value register remote temperature value register busy run/standby local temperature low limit comparator status register remote temperature low limit comparator remote temperature high limit comparator address pointer register one-shot register conversion rate register local temperature low limit register local temperature high limit register remote temperature low limit register local temperature high limit comparator remote temperature high limit register configuration register interrupt masking external diode open-circuit smbus interface adm1021a nc v dd nc gnd nc nc nc d+ d alert stby sdata sclk add0 add1 gnd nc = no connect low-cost microprocessor system temperature monitor * features alternative to the adm1021 on-chip and remote temperature sensing no calibration necessary 1 c accuracy for on-chip sensor 3 c accuracy for remote sensor programmable overtemperature/undertemperature limits programmable conversion rate 2-wire smbus serial interface supports system management bus (smbus) alert 200 ma max operating current 1 ma standby current 3 v to 5.5 v supply small 16-lead qsop package applications desktop computers notebook computers smart batteries industrial controllers telecom equipment instrumentation product description the adm1021a is a two-channel digital thermometer and undertemperature/overtemperature alarm, intended for use in personal computers and other systems requiring thermal monitor- ing and management. the device can measure the temperature of a microprocessor using a diode-connected pnp transistor, which may be provided on-chip in the case of the pentium iii or similar processors, or can be a low-cost discrete npn/pnp device such as the 2n3904/2n3906. a novel measurement technique cancels out the absolute value of the transistor? base emitter voltage, so that no calibration is required. the second measurement channel measures the output of an on-chip temperature sensor, to monitor the temperature of the device and its environment. the adm1021a communicates over a two-wire serial interface compatible with smbus standards. undertemperature and overtemperature limits can be programmed into the devices over the serial bus, and an alert output signals when the on-chip or remote temperature is out of range. this output can be used as an interrupt, or as an smbus alert. * patents pending
e2e rev. d adm1021aespecifications (t a = t min to t max 1 , v dd = 3.0 v to 3.6 v, unless otherwise noted.) parameter min typ max unit test conditions/comments power supply and adc temperature resolution 1
adm1021a e3e rev. d pin function descriptions pin no. mnemonic description 1, 5, 9, 13, 16 nc no connect 2v dd positive supply, 3 v to 5.5 v 3d + positive connection to remote temperature sensor 4d e negative connection to remote temperature sensor 6a dd1 three-state logic input, higher bit of device address 7, 8 gnd supply 0 v connection 10 a dd0 three-state logic input, lower bit of device address 11 alert open-drain logic output used as interrupt or smbus alert 12 sdata logic input/output, smbus serial data. open-drain output. 14 sclk logic input, smbus serial clock 15 stby logic input selecting normal operation (high) or standby mode (low) absolute maximum ratings * positive supply voltage (v dd ) to gnd . . . . . . e0.3 v to +6 v d+, add0, add1 . . . . . . . . . . . . . . . e0.3 v to v dd + 0.3 v de to gnd . . . . . . . . . . . . . . . . . . . . . . . . . . e0.3 v to +0.6 v sclk, sdata, alert , stby . . . . . . . . . . . e0.3 v to +6 v input current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
leakage resistance e m 20 15 e25 100 temperature error e c 10 1 0 e10 e15 e20 10 5 e5 e30 d+ to gnd d+ to v dd tpc 1. temperature error vs. pc board track resistance 3 1 0 2 frequency e hz 100 temperature error e c 4 5 100m 1k 10k 100k 1m 10m 250mv p-p remote 100mv p-p remote tpc 2. temperature error vs. power supply noise frequency 5 4 3 1 0 2 frequency e hz 1 temperature error e c 10 1k 10k 10m 100m 6 7 8 9 100 100k 1m 50mv p-p 100mv p-p 25mv p-p tpc 3. temperature error vs. common-mode noise frequency temperature e c 50 temperature error e c 60 0 70 80 100 120 e3 e1 1 2 e2 90 110 dev10 lower spec level upper spec level tpc 4. temperature error of adm1021a vs. pentium iii temperature capacitance e nf e1 2 temperature error e c 12 14 46810121 416182 02224 0 2 4 6 8 10 tpc 5. temperature error vs. capacitance between d+ and de sclk frequency e khz 1 supply current e a 20 0 v dd = 3.3v 51 02 55 07 5 100 1000 250 500 750 40 60 70 50 30 10 v dd = 5v tpc 6. standby supply current vs. clock frequency adm1021aetypical performance characteristics e4e rev. d
adm1021a e5e rev. d 4 0 2 frequency e hz temperature error e c 10mv p-p 100k 1m 10m 100m 1g 1 3 tpc 7. temperature error vs. differential-mode noise frequency conversion rate e hz 250 0.125 supply current e a 0.25 0.5 8 300 350 400 550 4 0.0625 450 500 200 150 100 50 5v 2 1 3.3v tpc 8. operating supply current vs. conversion rate 0 20 supply voltage e v 0 supply current e a 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 40 60 80 100 e20 tpc 9. standby supply current vs. supply voltage time e seconds temperature e c 0 25 50 75 100 125 remote temperature int temperature 0234 5678910 1 tpc 10. response to thermal shock functional description the adm1021a contains a two-channel a-to-d converter with special input-signal conditioning to enable operation with remote and on-chip diode temperature sensors. when the adm1021a is operat- ing normally, the a-to-d converter operates in a free-running mode. the analog input multiplexer alternately selects either the on-chip temperature sensor to measure its local temperature, or the remote temperature sensor. these signals are digitized by the adc and the results stored in the local and remote temperature value registers as 8-bit, twos complem ent words. the measurement results are compared with local and remote, high and low temperature limits, stored in four on-chip registers. out-of-limit comparisons generate flags that are stored in the status register, and one or more out-of-limit results will cause the alert output to pull low. the limit registers can be programmed, and the device con- trolled and configured, via the serial system management bus. the contents of any register can also be read back via the smbus. control and configuration functions consist of: switching the device between normal operation and standby mode. masking or enabling the alert output. selecting the conversion rate. on initial power-up, the remote and local temperature values default to e128
adm1021a e6e rev. d c1 * d+ de remote sensing transistor in i i bias v dd v out+ to adc v oute bias diode lowpass filter f c = 65khz capacitor c1 is optional. it is only necessary in noisy environments. c1 = 2.2nf typical, 3nf max. * figure 2. input signal conditioning the technique used in the adm1021a is to measure the change in v be when the device is operated at two different currents. this is given by: ? v be = kt / q n ) where: k is boltzmann?s constant, q is charge on the electron (1.6 t is absolute temperature in kelvins, n is ratio of the two currents. figure 2 shows the input signal conditioning used to measure the output of an external temperature sensor. this figure shows the external sensor as a substrate transistor, provided for tempera- ture monitoring on some microprocessors, but it could equally well be a discrete transistor. if a discrete transistor is used, the collector will not be grounded and should be linked to the base. to prevent ground noise 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 de input. if the sensor is operating in a noisy environment, c1 may optionally be added as a noise filter. its value is typically 2200 pf, but should be no more than 3000 pf. see the section on layout considerations for more information on c1. to measure ? ? actual range is 0 c to 127 c. the temperature data format is shown in table i. the results of the local and remote temperature measurements are stored in the local and remote temperature value registers, and are compared with limits programmed into the local and re mote high and low limit registers.
adm1021a e7e rev. d table iii. list of adm1021a registers read address (hex) write address (hex) name power-on default not applicable not applicable address pointer undefined 00 not applicable local temp. value 1000 0000 (80h) (e128
adm1021a e8e rev. d the alert interrupt latch is not reset by reading the status register, but will be reset when the alert output has been serviced by the master reading the device address, provided the error condition has gone away and the status register flag bits have been reset. configuration register t wo bits of the configuration register are used. if bit 6 is 0, which is the power-on default, the device is in ope rating mode with the adc converting. if bit 6 is set to 1, the device is in standby mode and the adc does not convert. standby mode can also be selected by taking the stby pin low. in standby mode the val- ues stored in the remote and local temperature registers remain at the value they were when the part was placed in standby. bit 7 of the configuration register is used to mask the alert out- put. if bit 7 is 0, which is the power-on default, the alert output is enabled. if bit 7 is set to 1, the alert output is disabled. table iv. configuration register bit assignments power-on bit name function default 7 mask1 0 = alert enabled 0 1 = alert masked 6 run/stop 0 = run 0 1 = standby 5e0 reserved 0 conversion rate register the lowest three bits of this register are used to program the con- vers ion rate by dividing the adc clock by 1, 2, 4, 8, 16, 32, 64, or 128, to give conversion times from 125 ms (code 07h) to 16 seconds (code 00h). this register can be written to and read back over the smb us. the higher five bits of this register are unused and must be set to zero. use of slower conversion times greatly reduces the device power consumption, as shown in t able v. table v. conversion rate register codes average supply current data conversion/sec
adm1021a e9e rev. d r/ w a6 sclk sdata a5 a4 a3 a2 a1 a0 d7 d6 d5 d4 d3 d2 d1 d0 ack. by adm1021a start by master 191 9 d7 d6 d5 d4 d3 d2 d1 d0 ack. by adm1021a stop by master 1 9 scl (continued) sda (continued) frame 1 serial bus address byte frame 3 data byte frame 2 address pointer register byte ack. by adm1021a figure 3. writing a register address to the address pointer register, then writing data to the selected register r/ w a6 sclk sdata a5 a4 a3 a2 a1 a0 d7 d6 d5 d4 d3 d2 d1 d0 ack. by adm1021a stop by master start by master 191 ack. by adm1021a 9 frame 1 serial bus address byte frame 2 address pointer register byte figure 4. writing to the address pointer register only r/ w a6 sclk sdata a5 a4 a3 a2 a1 a0 d7 d6 d5 d4 d3 d2 d1 d0 no ack. by master stop by master start by master 19 1 ack. by adm1021a 9 frame 1 serial bus address byte frame 2 data byte from adm1021a figure 5. reading data from a previously selected register 2. data is sent over the serial bus in sequences of nine clock pulses, eight bits of data followed by an acknowledge bit from the slave device. transitions on the data line must occur during the low period of the clock signal and remain stable during the high period, as a low-to-high transition when the clock is high may be interpreted as a stop signal. the number of data bytes that can be transmitted over the serial bus in a single read or write operation is limited only by w hat the master and slave devices can handle. 3. when all data bytes have been read or written, stop conditions are established. in write mode, the master will pull the data line high during the 10th clock pulse to assert a stop condition. in read mode, the master device will override the acknowledge bit by pulling the data line high during the low period before the ninth clock pulse. this is known as no acknowledge. the master will then take the data line low during the low period before the 10th clock pulse, then high during the 10th clock pulse to assert a stop condition. any number of bytes of data may be transferred over the serial bus in one operation, but it is not possible to mix read and write in one operation, because the type of operation is determined at the beginning and cannot subsequently be changed without starting a new operation. in the case of the adm1021a, write operations contain either one or two bytes, while read operations contain one byte. to write data to one of the device data registers or read data from it, the address pointer register must be set so that the correct data register is addressed, data can then be written into that register or read from it. the first byte of a write operation always contains a valid address that is stored in the address pointer register. if data is to be written to the device, the write operation contains a second data byte that is written to the reg- ister selected by the address pointer register.
adm1021a e10e rev. d this is illustrated in figure 3. the device address is sent over the bus followed by r/ w set to 0. this is followed by two data bytes. the first data byte is the address of the internal data reg- ister to be written to, which is stored in the address pointer register. the second data byte is the data to be written to the internal data register. when reading data from a register there are two possibilities: 1. if the adm1021a?s address pointer register value is un known or not the desired value, it is first necessary to set it to the correct value before data can be read from the desired data register. this is done by performing a write to the adm1021a as before, but only the data byte containing the register read address is sent, as data is not to be written to the register. this is shown in figure 4. a read operation is then performed consisting of the serial bus address, r/ w bit set to 1, followed by the data byte read from the data register. this is shown in figure 5. 2. if the address pointer register is known to be already at the desired address, data can be read from the corresponding data register without first writing to the address pointer reg ister, so figure 4 can be omitted. notes 1. although it is possible to read a data byte from a data register without first writing to the address pointer register, if the address pointer register is already at the correct value, it is not possible to write data to a register without writing to the address pointer register, because the first data byte of a write is always written to the address pointer register. 2. remember that the adm1021a registers have different addresses for read and write operations. the write address of a register must be written to the address pointer if data is to be written to that register, but it is not possible to read data from that address. the read address of a register must be written to the address pointer before data can be read from that register. alert output the alert output goes low whenever an out-of-limit mea- surement is detected, or if the remote temperature sensor is open-circuit. it is an open-drain and requires a 10 k ? smbalert smbalert m ar aarat t alert a rat alert smb amaar a alert alert smbalert ara alert lerstabmes tama stb br stb bama stb ba tsmb
adm1021a e11e rev. d applications information factors affecting accuracy remote sensing diode the adm1021a is designed to work with substrate transistors built into processors, or with discrete transistors. substrate transistors will generally be pnp types with the collector con nected to the substrate. discrete types can be either pnp or npn, connected as a diode (base shorted to collector). if an npn transistor is used, the collector and base are connected to d+ and the emitter to de. if a pnp transistor is used, the collector and base are connected to de and the emitter to d+. the user has no choice in the case of substrate transistors, but if a discrete transistor is used, the best accuracy will be obtained by choosing devices according to the following criteria: 1. base-emitter voltage greater than 0.25 v at 6 ?
adm1021a e12e rev. d 7. for really long distances (up to 100 feet), use shielded twisted pair such as belden #8451 microphone cable. connect the twisted pair to d+ and de and the shield to gnd close to the adm1021a. leave the remote end of the shield uncon- nected to avoid ground loops. because the measurement technique uses switched current sources, excessive cable and/or filter capacitance can affect the measure- ment. when using long cables, the filter capacitor may be reduced or removed. cable resistance can also introduce errors. 1 ? ? ?
adm1021a e13e rev. d outline dimensions 16-lead shrink small outline package [qsop] (rq-16) dimensions shown in inches 16 9 8 1 pin 1 seating plane 0.010 0.004 0.012 0.008 0.025 bsc 0.010 0.006 0.050 0.016 8 0 coplanarity 0.004 0.065 0.049 0.069 0.053 0.154 bsc 0.236 bsc compliant to jedec standards mo-137ab 0.193 bsc
adm1021a e14e rev. d revision history location page 3/04?data sheet changed from rev. c to rev. d. changes to features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 updated ordering guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 change to figure 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 4/03?data sheet changed from rev. b to rev. c. added esd caution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 updated outline dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3/02?data sheet changed from rev. a to rev. b. figures and tpcs renumbered . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . universal text change to figure 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 change to serial bus interface section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
adm1021a e15e rev. d
e16e c00056e0e3/04(d) adm1021a

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