LM88

Factory Programmable Dual Remote-Diode Thermostat

General Description

The LM88 is a dual remote-diode temperature sensor with 3

digital comparators. The LM88 has 3 open-drain outputs

(O_SP0, O_SP1 and O_CRIT) that can be used as inter-

rupts or to signal system shutdown. The digital comparators

can be factory programmed to make a greater than or less

than comparison. When programmed for a greater than

comparison outputs:

O_SP0 and O_SP1 activate when the temperatures mea-

sured by D0 or D1 exceed the associated setpoints of

T_SP0 or T_SP1.

O_CRIT activates when the temperature measured by

either D0 or D1 exceeds setpoint T_CRIT.

T_CRIT can be set at 1˚C intervals from −40˚C to +125˚C.

T_SP0 and T_SP1 can be set at 4˚C intervals in the range of

T_CRIT +127˚C/−128˚C. Hysteresis for all comparators is

set to 1˚C. O_CRIT, in conjunction with T_CRIT, could be

used to prevent catastrophic damage to key subsystems

such as notebook Card Bus cards while O_SP0 and O_SP1,

in conjunction with T_SP0 and T_SP1, can warn of an

impending failure.

The LM88 is available in an 8-lead mini-small-outline pack-

age.

Applications

n

Microprocessor Thermal Management

n

Appliances

n

Portable Battery Powered Systems

n

Fan Control

n

Industrial Process Control

n

HVAC Systems

n

Remote Temperature Sensing

n

Electronic System Protection

Features

n

2 external remote diode input channels

n

3 digital comparator outputs, 1 per remote diode and

one T_CRIT common to both

n

Factory programmable greater than or less than

comparisons

n

1˚C comparator hysteresis

n

2 setpoints, T_SP0 and T_SP1, factory programmable in

4˚C intervals

n

1 setpoint, T_CRIT, factory programmable in 1˚C

intervals

n

Active Low open-drain digital outputs

n

8-pin mini-SO plastic package

Key Specifications

2.8V–3.8V

1.5 mA (max)

−40˚C to +85˚C

Range

0˚C to +125˚C

j

Temperature Trip Point Accuracy:

Diode Junction

Temperature

(T

LM88CIM

Accuracy

LM88CIM

Temperature

Range

+45˚C to +85˚C

−40˚C to +85˚C

+60˚C to +100˚C

−40˚C to +85˚C

Note: These are sample ranges. Contact factory for other

ranges.

Simplified Block Diagram and Connection Diagram

MSOP-8/MUA08A Package

10132601

Top View

10132602

For simplicity, the effects of the hysteresis are not shown in the

temperature response diagram.

August 2001

© 2001 National Semiconductor Corporation

DS101326

www.national.com