ADM1021A AD | Alldatasheet
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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. 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 INTERFACEADM1021A NC VDD NC GND NC NC NC ALERT STBY SDATA SCLK ADD0 ADD1GND NC = NO CONNECT Low-Cost Microprocessor System Temperature Monitor*
FEATURES
Alternative to the ADM1021 On-Chip and Remote Temperature Sensing No Calibration Necessary 1/H11543C Accuracy for On-Chip Sensor 3/H11543C 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
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’s 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
–2– REV. D ADM1021A–SPECIFICATIONS(TA = TMIN to TMAX 1, VDD = 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 °C Guaranteed No Missed Codes Temperature Error, Local Sensor ± 1 °C –3 +3 °C Temperature Error, Remote Sensor –3 +3 °CT A = 60°C to 100°C –5 +5 °C Supply Voltage Range 3 3.6 V Note 2 Undervoltage Lockout Threshold 2.5 2.7 2.95 V V DD Input, Disables ADC, Rising Edge Undervoltage Lockout Hysteresis 25 mV Power-On Reset Threshold 0.9 1.7 2.2 V V DD, Falling Edge3 POR Threshold Hysteresis 50 mV Standby Supply Current 1 5 µAV DD = 3.3 V, No SMBus Activity 4 µA SCLK at 10 kHz Average Operating Supply Current 130 200 µA 0.25 Conversions/Sec Rate Autoconvert Mode, Averaged Over 4 Seconds 225 330 µA2 Conversions/Sec Rate Conversion Time 65 115 170 ms From Stop Bit to Conversion Complete (Both Channels) D+ Forced to D– + 0.65 V Remote Sensor Source Current 120 205 300 µAH igh Level 71 2 1 6 µAL ow Level3 D-Source Voltage 0.7 V Address Pin Bias Current (ADD0, ADD1) 50 µAM omentary at Power-On Reset SMBUS INTERFACE Logic Input High Voltage, V IH 2.2 V V DD = 3 V to 5.5 V STBY, SCLK, SDATA Logic Input Low Voltage, V IL 0.8 V V DD = 3 V to 5.5 V STBY, SCLK, SDATA SMBus Output Low Sink Current 6 mA SDATA Forced to 0.6 V ALERT Output Low Sink Current 1 mA ALERT Forced to 0.4 V Logic Input Current, I IH, IIL –1 +1 µA SMBus Input Capacitance, SCLK, SDATA 5 pF SMBus Clock Frequency 100 kHz SMBus Clock Low Time, t LOW 4.7 µst LOW between 10% Points SMBus Clock High Time, t HIGH 4 µst HIGH between 90% Points SMBus Start Condition Setup Time, t SU:STA 4.7 µs SMBus Repeat Start Condition 250 ns Between 90% and 90% Points Setup Time, tSU:STA SMBus Start Condition Hold Time, t HD:STA 4 µsT ime from 10% of SDATA to 90% of SCLK SMBus Stop Condition Setup Time, t SU:STO 4 µsT ime from 90% of SCLK to 10% of SDATA SMBus Data Valid to SCLK 250 ns Time from 10% or 90% of SDATA to 10% Rising Edge Time, t SU:DAT of SCLK SMBus Data Hold Time, t HD:DAT 0 µs SMBus Bus Free Time, t BUF 4.7 µsB etween Start/Stop Conditions SCLK Falling Edge to SDATA 1 µsM aster Clocking in Data Valid Time, tVD, DAT NOTES 1TMAX = 100°C; TMIN = 0°C. 2Operation at V DD = 5 V guaranteed by design, not production tested. 3Guaranteed by design, not production tested. Specifications subject to change without notice.
10 ADD0 Three-State Logic Input, Lower
11 ALERT Open-Drain Logic Output Used as
12 SDATA Logic Input/Output, SMBus Serial
14 SCLK Logic Input, SMBus Serial Clock
15 STBY Logic Input Selecting Normal
conditions for extended periods may affect device reliability. 16-Lead QSOP Package: θJA = 150°C/W. Figure 1. Diagram for Serial Bus Timing to avoid performance degradation or loss of functionality.
LEAKAGE RESISTANCE – M/H9024 –25 100 TEMPERATURE ERROR – /H11543C 101 –10 –15 –20 –30 D+ TO GND D+ TO VDD TPC 1. Temperature Error vs. PC Board Track Resistance FREQUENCY – Hz 100 TEMPERATURE ERROR – /H11543C 4 100M1k 10k 100k 1M 10M 250mV p-p REMOTE 100mV p-p REMOTE TPC 2. Temperature Error vs. Power Supply Noise Frequency FREQUENCY – Hz TEMPERATURE ERROR – /H11543C 10 1k 10k 10M 100M 100 100k 1M 50mV p-p 100mV p-p 25mV p-p TPC 3. Temperature Error vs. Common-Mode Noise Frequency TEMPERATURE – /H11543C TEMPERATURE ERROR – /H11543C 70 80 100 120 90 110 DEV10 LOWER SPEC LEVEL UPPER SPEC LEVEL TPC 4. Temperature Error of ADM1021A vs. Pentium III Temperature CAPACITANCE – nF TEMPERATURE ERROR – /H11543C 468 1 0 1 2 1 41 6 1 82 02 22 4 TPC 5. Temperature Error vs. Capacitance Between D+ and D– SCLK FREQUENCY – kHz SUPPLY CURRENT – /H9262A VDD = 3.3V 51 02 55 07 5 100 1000250 500 750 VDD = 5V TPC 6. Standby Supply Current vs. Clock Frequency ADM1021A–Typical Performance Characteristics –4– REV. D
–5–REV. D FREQUENCY – Hz TEMPERATURE ERROR – /H11543C 10mV p-p 100k 1M 10M 100M 1G TPC 7. Temperature Error vs. Differential-Mode Noise Frequency CONVERSION RATE – Hz 250 0.125 SUPPLY CURRENT – /H9262A 0.25 0.5 8 300 350 400 550 40.0625 450 500 200 150 100 3.3V TPC 8. Operating Supply Current vs. Conversion Rate SUPPLY VOLTAGE – V SUPPLY CURRENT – /H9262A 100 –20 TPC 9. Standby Supply Current vs. Supply Voltage TIME – Seconds TEMPERATURE – /H11543C 100 125 REMOTE TEMPERATURE INT TEMPERATURE 02 3 4 56789 1 01 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 –128°C. Since the device normally powers up converting, a measurement of local and remote temperature is made and these values are then stored before a comparison with the stored limits is made. However, if the part is powered up in standby mode (STBY pin pulled low), no new values are written to the register before a comparison is made. As a result, both RLOW and LLOW are tripped in the Status Register, thus generating an ALERT out- put. This may be cleared in one of two ways: 1. Change both the local and remote lower limits to –128 °C and read the status register (which in turn clears the ALERT output). 2. Take the part out of standby and read the status register (which in turn clears the ALERT output). This will work only if the measured values are within the limit values. MEASUREMENT METHOD A simple method of measuring temperature is to exploit the negative temperature coefficient of a diode, or the base-emitter voltage of a transistor, operated at constant current. Unfortu- nately, this technique requires calibration to null out the effect of the absolute value of V BE, which varies from device to device.
–7–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) (–128 °C) 01 Not Applicable Remote Temp. Value 1000 0000 (80h) (–128 °C)
02 Not Applicable Status Undefined
03 09 Configuration 0000 0000 (00h) 04 0A Conversion Rate 0000 0010 (02h) 05 0B Local Temp. High Limit 0111 1111 (7Fh) (+127 °C) 06 0C Local Temp. Low Limit 1100 1001 (C9h) (–55 °C) 07 0D Remote Temp. High Limit 0111 1111 (7Fh) (+127 °C) 08 0E Remote Temp. Low Limit 1100 1001 (C9h) (–55 °C) Not Applicable 0F
1 One-Shot
10 Not Applicable Reserved Undefined 2
11 11 Reserved Undefined 2 12 12 Reserved Undefined 2 13 13 Reserved Undefined 2 14 14 Reserved Undefined 2 15 16 Reserved Undefined 2 17 18 Reserved Undefined 2
19 Not Applicable Reserved Undefined 2
20 21 Reserved Undefined 2 FE Not Applicable Manufacturer Device ID 0100 0001 (41h) FF Not Applicable Die Revision Code 0011 xxxx (3xh) NOTES 1Writing to address 0F causes the ADM1021A to perform a single measurement. It is not a data register as such and it does not ma tter what data is written to it. 2These registers are reserved for future versions of the device. Table I. Temperature Data Format Temperature Digital Output 0°C0 000 0000 1°C0 000 0001 10°C0 000 1010 25°C0 001 1001 50°C0 011 0010 75°C0 100 1011 100°C0 110 0100 125°C0 111 1101 127°C0 111 1111 REGISTERS The ADM1021A contains nine registers that are used to store the results of remote and local temperature measurements, high and low temperature limits, and to configure and control the device. A description of these registers follows, and further details are given in Tables II to IV. It should be noted that the ADM1021A’s registers are dual port, and have different addresses for read and write operations. Attempting to write to a read address, or to read from a write address, will produce an invalid result. Register addresses above 0Fh are reserved for future use or used for factory test purposes and should not be written to. Address Pointer Register The Address Pointer Register itself does not have, nor does it require, an address, as it is the register to which the first data byte of every write operation is written automatically. This data byte is an address pointer that sets up one of the other registers for the second byte of the write operation, or for a subsequent read operation. Value Registers The ADM1021A has two registers to store the results of local and remote temperature measurements. These registers are written to by the ADC and can only be read over the SMBus. Status Register Bit 7 of the Status Register indicates when it is high that the ADC is busy converting. Bits 5 to 3 are flags that indicate the results of the limit comparisons. If the local and/or remote temperature measurement is above the corresponding high temperature limit or below the corresponding low temperature limit, then one or more of these flags will be set. Bit 2 is a flag that is set if the remote temperature sensor is open- circuit. These five flags are NOR’d together, so that if any of them is high, the ALERT interrupt latch will be set and the ALERT output will go low. Reading the Status Register will clear the five flag bits, provided the error conditions that caused the flags to be set have gone away. While a limit comparator is tripped due to a value register containing an out-of-limit measurement, or the sen- sor is open-circuit, the corresponding flag bit cannot be reset. A flag bit can only be reset if the corresponding value register con- tains an in-limit measurement, or the sensor is good. Table II. Status Register Bit Assignments Bit Name Function
7 BUSY 1 When ADC Converting
6 LHIGH* 1 When Local High Temp Limit Tripped
5 LLOW* 1 When Local Low Temp Limit Tripped
4 RHIGH* 1 When Remote High Temp Limit Tripped
3 RLOW* 1 When Remote Low Temp Limit Tripped
2 OPEN* 1 When Remote Sensor Open-Circuit
1–0 Reserved *These flags stay high until the status register is read or they are reset by POR.
–8– 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 Two 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 5–0 Reserved 0 Conversion Rate Register The lowest three bits of this register are used to program the con- version 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 SMBus. 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 µA Typ at VCC = 3.3 V 00h 0.0625 150 01h 0.125 150 02h 0.25 150 03h 0.5 150 04h 1 150 05h 2 150 06h 4 160 07h 8 180 08h to FFh Reserved Limit Registers The ADM1021A has four limit registers to store local and remote, high and low temperature limits. These registers can be w ritten to and read back over the SMBus. The high limit registers perform a > comparison while the low limit registers perform a < comparison. For example, if the high limit register is pro- grammed as a limit of 80 °C, measuring 81 °C will result in an alarm condition. Even though the temperature measurement range is from 0 /H11543 to 127 °C, it is possible to program the limit register w ith negative values. This is for backwards-compatibility with the ADM1021. One-Shot Register The one-shot register is used to initiate a single conversion and comparison cycle when the ADM1021A is in standby mode, after which the device returns to standby. This is not a data register as such and it is the write operation that causes the one- shot conversion. The data written to this address is irrelevant and is not stored. SERIAL BUS INTERFACE Control of the ADM1021A is carried out via the serial bus. The ADM1021A is connected to this bus as a slave device, under the control of a master device. Note that the SMBus and SCL pins are three-stated when the ADM1021A is powered down and will not pull down the SMBus. ADDRESS PINS In general, every SMBus device has a 7-bit device address (except for some devices that have extended, 10-bit addresses). When the master device sends a device address over the bus, the slave device with that address will respond. The ADM1021A has two address pins, ADD0 and ADD1, to allow selection of the device address, so that several ADM1021As can be used on the same bus, and/or to avoid conflict with other devices. Although only two address pins are provided, these are three-state, and can be grounded, left unconnected, or tied to V DD, so that a total of nine different addresses are possible, as shown in Table VI. It should be noted that the state of the address pins is only sampled at power-up, so changing them after power-up will have no effect. Table VI. Device Addresses ADD0 ADD1 Device Address 00 0011 000 0N C 0011 001 01 0011 010 NC 0 0101 001 NC NC 0101 010 NC 1 0101 011 10 1001 100 1N C 1001 101 11 1001 110 ADD0, ADD1 sampled at power-up only. The serial bus protocol operates as follows: 1. The master initiates data transfer by establishing a START condition, defined as a high-to-low transition on the serial data line SDATA, while the serial clock line SCLK remains high. This indicates that an address/data stream will follow. All slave peripherals connected to the serial bus respond to the START condition and shift in the next eight bits, consisting of a 7-bit address (MSB first) plus an R/ W bit, which deter- mines the direction of the data transfer, i.e., whether data will be written to or read from the slave device. The peripheral whose address corresponds to the transmitted address responds by pulling the data line low during the low period before the ninth clock pulse, known as the Acknowl- edge Bit. All other devices on the bus now remain idle while the selected device waits for data to be read from or written to it. If the R/ W bit is a 0, the master will write to the slave device. If the R/ W bit is a 1, the master will read from the slave device.
- If the ADM1021A’s Address Pointer Register value is unknown
address is sent, as data is not to be written to the register. from the data register. This is shown in Figure 5.
- If the Address Pointer Register is known to be already at the
- Although it is possible to read a data byte from a data register
write is always written to the Address Pointer Register.
- Remember that the ADM1021A registers have different
to talk, but the SMBALERT function allows them to do so. occurs as illustrated in Figure 6. Figure 6. Use of SMBALERT
- Master initiates a read operation and sends the Alert Response
that must not be used as a specific device address.
- The device whose ALERT output is low responds to the Alert
- If more than one device’s ALERT output is low, the one with
- Once the ADM1021A has responded to the Alert Response
STBY is high, or Bit 6 is low, the ADM1021A operates normally. result to the corresponding value register. or 100 µA if there are clock and data signals on the bus. ated by writing XXh to the One-Shot Register (address 0Fh). can be interpreted as a fault condition. measurement as a fault condition.
base are connected to D– and the emitter to D+.
- Base-emitter voltage greater than 0.25 V at 6 µA, at the high-
- Base-emitter voltage less than 0.95 V at 100 µA, at the lowest
- Base resistance less than 100 Ω.
control of VBE characteristics. package are suitable devices to use. QSOP-16 package is about 10 seconds. due to self-heating will be negligible.
- Place the ADM1021A as close as possible to the remote
this distance can be four to eight inches.
- Route the D+ and D– tracks close together, in parallel, with
under the tracks if possible.
- Use wide tracks to minimize inductance and reduce noise pickup.
10 mil track minimum width and spacing is recommended.
- Try to minimize the number of copper/solder joints, which
and at the same temperature. them, thermocouple voltages should be much less than 240µV.
- Place a 0.1 µF bypass capacitor close to the V
Figure 7. Arrangement of Signal Tracks
- If the distance to the remote s ensor is more than eight inches,
- For really long distances (up to 100 feet), use shielded twisted
nected to avoid ground loops. Figure 8. Typical Application Circuit
2 USB PORTS
2 IDE PORTS
Figure 9. Typical System Using ADM1021A
–13–REV. D OUTLINE DIMENSIONS 16-Lead Shrink Small Outline Package [QSOP] (RQ-16) Dimensions shown in inches 16 9 PIN 1 SEATING PLANE 0.010 0.004 0.012 0.008 0.025 BSC 0.010 0.006 0.050 0.016 8/H11543 0/H11543 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
–14– REV. D
Revision History
3/04—Data Sheet changed from REV. C to REV. D. 4/03—Data Sheet changed from REV. B to REV. C. 3/02—Data Sheet changed from REV. A to REV. B.
–15–REV. D
–16– C00056–0–3/04(D) ADM1021A