LM82

Remote Diode and Local Digital Temperature Sensor

with Two-Wire Interface

General Description

The LM82 is a digital temperature sensor with a 2 wire serial

interface that senses the voltage and thus the temperature of

a remote diode using a Delta-Sigma analog-to-digital con-

verter with a digital over-temperature detector. The LM82

accurately senses its own temperature as well as the tem-

sors or diode connected 2N3904s. The temperature of any

ASIC can be detected using the LM82 as long as a dedi-

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

Using the SMBus interface a host can access the LM82’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

programmable comparator HIGH limit.

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

T_CRIT register and the 2 T_HIGH registers. Three state

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

SMBus address locations for the LM82. The sensor powers

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

T_HIGHs. The LM82 is pin for pin and register compatible

with the LM84, Maxim MAX1617 and Analog Devices

ADM1021.

Features

n

Accurately senses die temperature of 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 LM82s on a

single bus

Key Specifications

3.0V to 3.6V

0.8mA (max)

0˚C to +85˚C

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

10129701

August 2004

© 2004 National Semiconductor Corporation

DS101297

www.national.com