±1°C Temperature Monitor with

Series Resistance Cancellation

ADT7461*

FEATURES

On-chip and remote temperature sensor

0.25°C resolution/1°C accuracy on remote channel

1°C resolution/3°C accuracy on local channel

Automatically cancels up to 3 kΩ (typ) of resistance in series

with remote diode to allow noise filtering

Extended, switchable temperature measurement range 0°C

to +127°C (default) or –55°C to +150°C

Pin and register compatible with ADM1032

2-wire SMBus serial interface with SMBus alert support

Programmable over/under temperature limits

Offset registers for system calibration

Up to 2 overtemperature fail-safe THERM outputs

Small 8-lead SOIC or MSOP package

170 µA operating current, 5.5 µA standby current

APPLICATIONS

Desktop and notebook computers

Industrial controllers

Smart batteries

Automotive

Enbedded systems

Burn-in applications

Instrumentation

PRODUCT DESCRIPTION

The ADT7461 is a dual-channel digital thermometer and

under/over temperature alarm, intended for use in PCs and

thermal management systems. It is pin and register compatible

with the ADM1032. The ADT7461 has three additional features:

series resistance cancellation, where up to 3 kΩ (typical) of

resistance in series with the temperature monitoring diode may

be automatically cancelled from the temperature result, allowing

noise filtering; configurable ALERT output; and an extended,

switchable temperature measurement range.

The ADT7461 can measure the temperature of a remote ther-

mal diode accurate to ±1°C, and the ambient temperature accu-

rate to ±3°C. The temperature measurement range defaults to

0°C to +127°C, compatible with ADM1032, but can be switched

to a wider measurement range, from −55°C to +150°C. The

ADT7461 communicates over a 2-wire serial interface compati-

ble with system management bus (SMBus) standards. An

ALERT output signals when the on-chip or remote temperature

is out of range. The THERM output is a comparator output that

allows on/off control of a cooling fan. The ALERT output can

be reconfigured as a second THERM output if required.

*Protected by U.S. Patents

6,097,239; 6,133,753; 6,169,442; other patents pending.

SCLK

SDATA

GND

6

4

ADDRESS POINTER

REGISTER

LOCAL TEMPERATURE

LOW LIMIT REGISTER

LOCAL TEMPERATURE

HIGH LIMIT REGISTER

REMOTE TEMPERATURE

LOW LIMIT REGISTER

REMOTE TEMPERATURE

HIGH LIMIT REGISTER

LOCAL TEMPERATURE

VALUE REGISTER

REMOTE TEMPERATURE

VALUE REGISTER

ADC

ANALOG

MUX

ON-CHIP

TEMPERATURE

SENSOR

RUN/STANDBY

BUSY

REMOTE OFFSET

REGISTER

EXTERNAL DIODE OPEN-CIRCUIT

ADT7461

STATUS REGISTER

SMBus INTERFACE

LOCAL THERM LIMIT

REGISTER

EXTERNAL THERM LIMIT

REGISTER

CONFIGURATION

REGISTER

INTERRUPT

MASKING

7

5

1

8

THERM

ALERT/

THERM2

D+

D–

SRC

BLOCK

2

3

CONVERSION RATE

REGISTER

Figure 1. Functional Block Diagram

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infringements of patents or other rights of third parties that may result from its use.

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registered trademarks are the property of their respective owners.

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© 2003 Analog Devices, Inc. All rights reserved.

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