Low Cost Microprocessor
System Temperature Monitor
a
ADM1021
FEATURES
PRODUCT DESCRIPTION
Improved Replacement for MAX1617
On-Chip and Remote Temperature Sensing
No Calibration Necessary
The ADM1021 is a two-channel digital thermometer and under/
over temperature alarm, intended for use in personal computers
and other systems requiring thermal monitoring and manage-
ment. The device can measure the temperature of a micropro-
cessor using a diode-connected PNP transistor, which may be
provided on-chip in the case of the Pentium® II or similar pro-
cessors, 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 chan-
nel measures the output of an on-chip temperature sensor, to
monitor the temperature of the device and its environment.
1؇C Accuracy for On-Chip Sensor
3؇C Accuracy for Remote Sensor
Programmable Over/Under Temperature Limits
Programmable Conversion Rate
2-Wire SMBus Serial Interface
Supports System Management Bus (SMBus™) Alert
70 A Max Operating Current
3 A Standby Current
3 V to 5.5 V Supply
Small 16-Lead QSOP Package
The ADM1021 communicates over a two-wire serial interface
compatible with SMBus standards. Under and over temperature
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 inter-
rupt, or as an SMBus alert.
APPLICATIONS
Desktop Computers
Notebook Computers
Smart Batteries
Industrial Controllers
Telecomms Equipment
Instrumentation
FUNCTIONAL BLOCK DIAGRAM
ADDRESS POINTER
REGISTER
ONE-SHOT
REGISTER
CONVERSION RATE
REGISTER
LOCAL TEMPERATURE
LOW LIMIT REGISTER
LOCAL TEMPERATURE
VALUE REGISTER
LOCAL TEMPERATURE
LOW LIMIT COMPARATOR
ON-CHIP TEMP.
SENSOR
LOCAL TEMPERATURE
HIGH LIMIT COMPARATOR
LOCAL TEMPERATURE
HIGH LIMIT REGISTER
D+
D–
8-BIT A-TO-D
CONVERTER
ANALOG MUX
REMOTE TEMPERATURE
LOW LIMIT REGISTER
REMOTE TEMPERATURE
LOW LIMIT COMPARATOR
BUSY
RUN/STANDBY
REMOTE TEMPERATURE
HIGH LIMIT REGISTER
REMOTE TEMPERATURE
VALUE REGISTER
REMOTE TEMPERATURE
HIGH LIMIT COMPARATOR
CONFIGURATION
REGISTER
STBY
EXTERNAL DIODE OPEN-CIRCUIT
INTERRUPT
MASKING
ALERT
STATUS REGISTER
SMBUS INTERFACE
ADM1021
TEST
V
NC
GND GND
NC
NC
TEST
SDATA
SCLK
ADD0
ADD1
DD
SMBus is a trademark and Pentium is a registered trademark of Intel Corporation.
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
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Tel: 781/329-4700
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© Analog Devices, Inc., 1998