PDF ADM1023 Data sheet ( Hoja de datos )

Número de pieza	ADM1023
Descripción	ACPI-Compliant High-Accuracy Microprocessor System Temperature Monitor
Fabricantes	Analog Devices
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No Preview Available ! a ACPI-Compliant High-Accuracy Microprocessor System Temperature Monitor ADM1023* FEATURES Next Generation Upgrade to ADM1021 On-Chip and Remote Temperature Sensing Offset Registers for System Calibration 1؇C Accuracy and Resolution on Local Channel 0.125؇C Resolution/1؇C Accuracy on Remote Channel Programmable Over/Under Temperature Limits Programmable Conversion Rate Supports System Management Bus (SMBus) Alert 2-Wire SMBus Serial Interface 200 ␮A Max Operating Current (0.25 Conversions/ Seconds) 1 ␮A Standby Current 3 V to 5.5 V Supply Small 16-Lead QSOP Package APPLICATIONS Desktop Computers Notebook Computers Smart Batteries Industrial Controllers Telecomms Equipment Instrumentation PRODUCT DESCRIPTION The ADM1023 is a two-channel digital thermometer and under/ over temperature alarm, intended for use in personal computers and other systems requiring thermal monitoring and management. Optimized for the Pentium® III; the higher accuracy offered allows systems designers to safely reduce temperature guard banding and increase system performance. The device can measure the temperature of a microprocessor using a diode-con- nected 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 tem- perature of the device and its environment. The ADM1023 communicates over a 2-wire serial interface compatible with SMBus standards. Under and over tempera- ture limits can be programmed into the device 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. FUNCTIONAL BLOCK DIAGRAM ON-CHIP TEMPERATURE SENSOR LOCAL TEMPERATURE VALUE REGISTER D+ ANALOG A-TO-D D– MUX CONVERTER BUSY RUN/STANDBY REMOTE TEMPERATURE VALUE REGISTERS EXTERNAL DIODE OPEN-CIRCUIT ADM1023 LOCAL TEMPERATURE LOW-LIMIT COMPARATOR LOCAL TEMPERATURE HIGH-LIMIT COMPARATOR REMOTE TEMPERATURE LOW-LIMIT COMPARATOR REMOTE TEMPERATURE HIGH-LIMIT COMPARATOR STATUS REGISTER ADDRESS POINTER REGISTER ONE-SHOT REGISTER CONVERSION RATE REGISTER OFFSET REGISTERS LOCAL TEMPERATURE LOW-LIMIT REGISTER LOCAL TEMPERATURE HIGH-LIMIT REGISTER REMOTE TEMPERATURE LOW-LIMIT REGISTERS REMOTE TEMPERATURE HIGH-LIMIT REGISTERS CONFIGURATION REGISTER INTERRUPT MASKING SMBUS INTERFACE STBY ALERT NC VDD NC GND GND NC *Patents pending. Pentium is a registered trademark of Intel Corporation. REV. A NC NC NC = NO CONNECT SDATA SCLK ADD0 ADD1 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 which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 © Analog Devices, Inc., 2000 1 page ADM1023 4 100 3 10mV p-p 2 80 60 40 20 1 0 0 100k 1M 10M 100M FREQUENCY – Hz 1G Figure 8. Temperature Error vs. Differential-Mode Noise Frequency –20 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE – V Figure 10. Standby Supply Current vs. Supply Voltage 550 500 450 400 350 300 250 200 3.3 VOLTS 150 100 50 0.0625 0.125 5 VOLTS 0.25 0.5 1 2 CONVERSION RATE – Hz 4 8 Figure 9. Operating Supply Current vs. Conversion Rate, VDD = 5 V and 3 V 125 REMOTE TEMPERATURE 100 INT 75 TEMPERATURE 50 25 0 0 1 2 3 4 5 6 7 8 9 10 TIME – Seconds Figure 11. Response to Thermal Shock FUNCTIONAL DESCRIPTION The ADM1023 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 ADM1023 is operating 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 are stored in the Local and Remote Temperature Value Registers. Only the eight most signiﬁcant bits of the local temperature value are stored as an 8-bit binary word. The remote temperature value is stored as an 11-bit, binary word in two registers. The eight MSBs are stored in the Remote Temperature Value High Byte Register at address 01h. The three LSBs are stored, left-justiﬁed, in the Remote Temperature Value High Byte Register at address 10h. Error sources such as PCB track resistance and clock noise can introduce offset errors into measurements on the Remote Channel. To achieve the speciﬁed accuracy on this channel, these offsets must be removed, and two Offset Registers are provided for this purpose at addresses 11h and 12h. An offset value may automatically be added to or subtracted from the measurement by writing an 11 bit, two’s complement value to registers 11h (high byte) and 12h (low byte, left- justiﬁed). The offset registers default to zero at power-up and will have no effect if nothing is written to them. The measurement results are compared with Local and Remote, High and Low Temperature Limits, stored in six on-chip Limit Registers. As with the measured value, the local temperature limits are stored as 8-bit values and the remote temperature limits as 11-bit values. 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. Registers can be programmed, and the device controlled and conﬁgured, via the serial System Management Bus. The con- tents 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 convert- ing, a measure of local and remote temperature is made and these REV. A –5– 5 Page ADM1023 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 kΩ pull-up to VDD. Several ALERT outputs can be wire-ANDED together, so that the common line will go low if one or more of the ALERT outputs goes low. The ALERT output can be used as an interrupt signal to a pro- cessor, or it may be used as an SMBALERT. Slave devices on the SMBus normally cannot signal to the master they want to talk, but the SMBALERT function allows them to do so. One or more ALERT outputs are connected to a common SMBALERT line connected to the master. When the SMBALERT line is pulled low by one of the devices, the following procedure occurs as illustrated in Figure 17. MASTER RECEIVES SMBALERT START ALERT RESPONSE ADDRESS RD ACK DEVICE ADDRESS NO ACK STOP MASTER SENDS ARA AND READ COMMAND DEVICE SENDS ITS ADDRESS Figure 17. Use of SMBALERT 1. SMBALERT pulled low. 2. Master initiates a read operation and sends the Alert Response Address (ARA = 0001 100). This is a general call address that must not be used as a speciﬁc device address. 3. The device whose ALERT output is low responds to the Alert Response Address and the master reads its device address. The address of the device is now known and it can be inter- rogated in the usual way. 4. If more than one device’s ALERT output is low, the one with the lowest device address, will have priority, in accordance with normal SMBus arbitration. 5. Once the ADM1023 has responded to the Alert Response Address, it will reset its ALERT output, provided that the error condition that caused the ALERT no longer exists. If the SMBALERT line remains low, the master will send ARA again, and so on until all devices whose ALERT outputs were low have responded. LOW POWER STANDBY MODES The ADM1023 can be put into a low power standby mode using hardware or software, that is, by taking the STBY input low, or by setting Bit 6 of the Conﬁguration Register. When STBY is high, or Bit 6 is low, the ADM1023 operates normally. When STBY is pulled low or Bit 6 is high, the ADC is inhibited, any conversion in progress is terminated without writing the result to the correspond- ing value register. The SMBus is still enabled. Power consumption in the standby mode is reduced to less than 10 µA if there is no SMBus activ- ity, or 100 µA if there are clock and data signals on the bus. These two modes are similar but not identical. When STBY is low, conversions are completely inhibited. When Bit 6 is set but STBY is high, a one-shot conversion of both channels can be initiated by writing any data value to the One-Shot Register (Address 0Fh). SENSOR FAULT DETECTION The ADM1023 has a fault detector at the D+ input that detects if the external sensor diode is open-circuit. This is a simple voltage comparator that trips if the voltage at D+ exceeds VCC – 1 V (typical). The output of this comparator is checked when a conver- sion is initiated, and sets Bit 2 of the Status Register if a fault is detected. If the remote sensor voltage falls below the normal measuring range, for example, due to the diode being short-circuited, the ADC will output –128°C (1000 0000 000). Since the normal operating temperature range of the device only extends down to 0°C, this output code will never be seen in normal operation, so it can be interpreted as a fault condition. In this respect, the ADM1023 differs from and improves upon competitive devices that output zero if the external sensor goes short-circuit. These devices can misinterpret a genuine 0°C mea- surement as a fault condition. If the external diode channel is not being used and is shorted out, the resulting ALERT may be cleared by writing 80h (–128°C) to the low limit register. APPLICATIONS INFORMATION FACTORS AFFECTING ACCURACY Remote Sensing Diode The ADM1023 is designed to work with substrate transistors built into processors, or with discrete transistors. Substrate tran- sistors will generally be PNP types with the collector connected to the substrate. Discrete types can be either PNP or NPN, con- nected as a diode (base shorted to collector). If an NPN transistor is used then the collector and base are connected to D+ and the emitter to D–. If a PNP transistor is used, the collector and base are connected to D– 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 µA, at the high- est operating temperature. 2. Base-emitter voltage less than 0.95 V at 100 µA, at the lowest operating temperature. 3. Base resistance less than 100 ⍀. 4. Small variation in hfe (say 50 to 150) which indicates tight control of VBE characteristics. Transistors such as 2N3904, 2N3906 or equivalents in SOT-23 package are suitable devices to use. Thermal Inertia and Self-Heating Accuracy depends on the temperature of the remote-sensing diode and/or the internal temperature sensor being at the same temperature as that being measured; and a number of factors can affect this. Ideally, the sensor should be in good thermal contact with the part of the system being measured, for example the processor. If it is not, the thermal inertia caused by the mass of the sensor will cause a lag in the response of the sensor to a temperature change. In the case of the remote sensor this should not be a problem, as it will be either a substrate transistor in the processor or a small package device such as SOT-23 placed in close proximity to it. The on-chip sensor, however, will often be remote from the pro- cessor and will only be monitoring the general ambient temperature REV. A –11– 11 Page

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