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.

a

ADM1020

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., 1999

8-Lead, Low-Cost, System

Temperature Monitor

FUNCTIONAL BLOCK DIAGRAM

LOCAL TEMPERATURE

LOW LIMIT COMPARATOR

LOCAL TEMPERATURE

HIGH LIMIT COMPARATOR

REMOTE TEMPERATURE

LOW LIMIT COMPARATOR

REMOTE TEMPERATURE

HIGH LIMIT COMPARATOR

REMOTE TEMPERATURE

VALUE REGISTER

LOCAL TEMPERATURE

VALUE REGISTER

RUN/STANDBY

8-BIT A-TO-D

CONVERTER

BUSY

ANALOG

MUX

ON-CHIP TEMP.

SENSOR

D+

D–

STATUS REGISTER

LOCAL TEMPERATURE

LOW LIMIT REGISTER

LOCAL TEMPERATURE

HIGH LIMIT REGISTER

REMOTE TEMPERATURE

LOW LIMIT REGISTER

REMOTE TEMPERATURE

HIGH LIMIT REGISTER

CONFIGURATION

REGISTER

CONVERSION RATE

REGISTER

ONE-SHOT

REGISTER

ADDRESS POINTER

REGISTER

INTERRUPT

MASKING

ALERT

ADM1020

SMBUS INTERFACE

EXTERNAL DIODE OPEN-CIRCUIT

GND

SDATA

SCLK

ADD

PRODUCT DESCRIPTION

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 transis-

tor, 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 chan-

nel 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.

SMBus is a trademark of Intel Corporation.

Pentium is a registered trademark of Intel Corporation.

FEATURES

On-Chip and Remote Temperature Sensing

No Calibration Necessary

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 SMBus Alert

70

A Max Operating Current

3

A Standby Current

+3 V to +5.5 V Supply

8-Lead SOIC Package

APPLICATIONS

Desktop Computers

Notebook Computers

Smart Batteries

Industrial Controllers

Telecommunication Equipment

Instrumentation