ADM1020

The ADM1020 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. The device can measure the temperature of a microprocessor using a diode-connected NPN or PNP transistor, which may be provided on-chip in the case of the Pentium® II or similar processors, or can be a low-cost discrete device such as the 2N3904. 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 ADM1020 communicates over a two-wire serial interface compatible with System Management Bus (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 interrupt, or as an SMBus alert.