LM83

Triple-Diode Input and Local Digital Temperature Sensor

with Two-Wire Interface

General Description

The LM83 is a digital temperature sensor with a 2 wire serial

interface that senses the voltage and thus the temperature of

three remote diodes using a Delta-Sigma analog-to-digital

converter with a digital over-temperature detector. The LM83

accurately senses its own temperature as well as the tem-

cessors or diode connected 2N3904s. The temperature of

any ASIC can be detected using the LM83 as long as a dedi-

cated diode (semiconductor junction) is available on the die.

Using the SMBus interface a host can access the LM83’s

registers at any time. Activation of a T_CRIT_A output oc-

curs when any temperature is greater than a programmable

comparator limit, T_CRIT. Activation of an INT output occurs

when any temperature is greater than its corresponding pro-

grammable comparator HIGH limit.

The host can program as well as read back the state of the

T_CRIT register and the four T_HIGH registers. Three state

logic inputs allow two pins (ADD0, ADD1) to select up to 9

SMBus address locations for the LM83. The sensor powers

up with default thresholds of 127˚C for T_CRIT and all

T_HIGHs. The LM83 is pin for pin and register compatible

with the LM84 as well as the Maxim MAX1617 and the Ana-

log Devices ADM1021.

Features

n Accurately senses die temperature of 3 remote ICs, or

diode junctions

n On-board local temperature sensing

n SMBus and I

SMBus 1.1 TIMEOUT

n Two interrupt outputs: INT and T_CRIT_A

n Register readback capability

n 7 bit plus sign temperature data format, 1 ˚C resolution

n 2 address select pins allow connection of 9 LM83s on a

single bus

Key Specifications

n Supply Voltage

3.0V to 3.6V

n Supply Current

0.8mA (max)

n Local Temp Accuracy (includes quantization error)

0˚C to +85˚C

n Remote Diode Temp Accuracy (includes quantization

error)

+25˚C to +100˚C

0˚C to +125˚C

Applications

n System Thermal Management

n Computers

n Electronic Test Equipment

n Office Electronics

n HVAC

Simplified Block Diagram

DS101058-1

November 1999

© 1999 National Semiconductor Corporation

DS101058

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