© Semiconductor Components Industries, LLC, 2010

June, 2010 − Rev. 8

1

Publication Order Number:

ADM1021A/D

ADM1021A

Low Cost Microprocessor

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.

FEATURES

APPLICATIONS

http://onsemi.com

See detailed ordering and shipping information in the package

dimensions section on page 14 of this data sheet.

ORDERING INFORMATION

xxx

= Device Code

#

= Pb−Free Package

YYWW = Date Code

MARKING DIAGRAM

1

QSOP−16

CASE 492

1021AA

RQZ

#YYWW

1

2

3

4

5

6

7

8

ADM1021A

TOP VIEW

14

13

12

11

10

9

D+

D–

GND

ADD1

NC

NC

ADD0

GND

NC

ALERT

SDATA

NC

16

15

NC

STBY

SCLK

PIN ASSIGNMENT