LM91

Diode Input Digital Temperature Sensor with Two-Wire

Interface

General Description

The

LM91

is

a

remote

diode

temperature

sensor,

Delta-Sigma

analog-to-digital

converter,

and

digital

LM91 senses its own temperature as well as the tempera-

II processor or a diode connected 2N3904. A diode junction

(semiconductor junction) is required on the target IC’s die. A

host can query the LM91 at any time to read the temperature

of this diode as well as the temperature state of the LM91

itself. A T_CRIT_A interrupt output becomes active when the

temperature is greater than a programmable comparator

limit, T_CRIT.

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

T_CRIT register. Power up default values for T_CRIT are as

shown in the ordering information table. Three state logic

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

address locations for the LM91.

Features

n

Directly senses die temperature of remote ICs

n

Senses temperature of remote diodes

n

SMBus compatible interface, supports SMBus Timeout

n

Register readback capability

n

7 bit plus sign temperature data format

n

2 address select lines enable 9 LM91s to be connected

to a single bus

Key Specifications

3.0V - 3.6V

1 mA (max)

+60˚C to +100˚C

0˚C to +125˚C

Applications

n

System Thermal Management

n

Personal Computers

n

Electronic Test Equipment

n

Office Electronics

n

HVAC

Simplified Block Diagram

20034301

# Indicates Active Low (”NOT“)

November 2001

© 2001 National Semiconductor Corporation

DS200343

www.national.com