General Description

The LM84 is a remote diode temperature sensor,

Delta-Sigma analog-to-digital converter, and digital

over-temperature detector with an SMBus™ interface. The

LM84 senses its own temperature as well as the temperature

of a target IC with a diode junction, such as a Pentium®

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 LM84 at any time to read the temperature

of this diode as well as the temperature state of the LM84

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. Three state logic inputs allow two pins

(ADD0, ADD1) to select up to 9 SMBus address locations for

the LM84. The sensor powers up with default thresholds of

127°C for T_CRIT.

Features

Directly senses die temperature of remote ICs

Senses temperature of remote diodes

SMBus compatible interface, supports SMBus Timeout

Register readback capability

7 bit plus sign temperature data format

2 address select lines enable 9 LM84s to be connected

to a single bus

Key Specifications

Supply Voltage 3.0V - 3.6V

Supply Current 1 mA (max)

Local Temperature Accuracy ±1.0°C (typ)

Remote Diode Temperature Accuracy

+60°C to +100°C ±3°C (max)

0°C to +125°C ±5°C (max)

Applications

System Thermal Management

Personal Computers

Electronic Test Equipment

Office Electronics

HVAC