Temperature monitor
ON Semiconductor
System Temperature
Monitor Microcomputer
The ADM1021A is a two−channel digital thermometer and
under/overtemperature alarm, intended for use in personal computers
and other systems requiring thermal monitoring and management. The
device can measure the temperature of a microprocessor using a
diode−connected PNP transistor, which can be provided on−chip with
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. Under/overtemperature 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.
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