LM81CIMT-31 National Semiconductor, LM81CIMT-31 Datasheet

LM81CIMT-31

Manufacturer Part Number

LM81CIMT-31

Description

Serial Interface ACPI-Compatible Microprocessor System

Manufacturer

National Semiconductor

Datasheet

1.LM81CIMT-31.pdf (32 pages)

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LM81

Serial Interface ACPI-Compatible Microprocessor System

Hardware Monitor

General Description

The LM81 is a highly integrated data acquisition system for

hardware monitoring of servers, Personal Computers, or vir-

tually any microprocessor-based system. In a PC, the LM81

can be used to monitor power supply voltages, tempera-

tures, and fan speeds. Actual values for these inputs can be

read at any time. Programmable WATCHDOG

LM81 activate a fully programmable and maskable interrupt

system with two outputs (INT and T_CRIT_).

The LM81 has an on-chip digital output temperature sensor

with 9-bit or 12-bit resolution, a 6 analog input ADC with 8-bit

resolution and an 8-bit DAC. Two fan tachometer outputs

can be measured with the LM81’s FAN1 and FAN2 inputs.

The DAC, with a 0 to 1.25V output voltage range, can be

used for fan speed control. Additional inputs are provided for

Chassis Intrusion detection circuits, and VID monitor inputs.

The LM81 has a Serial Bus interface that is compatible with

SMBus

Features

n Temperature sensing

n 6 positive voltage inputs with scaling resistors for

n 8-bit DAC output for controlling fan speed

Typical Application

# Indicates Active Low (“Not”)

TRI-STATE

WATCHDOG

SMBus

monitoring +5V, +12V, +3.3V, +2.5V, Vccp power

supplies directly

™

is a trademark of the Intel Corporation.

™

is a registered trademark of National Semiconductor Corporation.

™

is a trademark of National Semiconductor Corporation.

DS100072

™

limits in the

n 2 fan speed monitoring inputs

n Chassis Intrusion Detector input

n WATCHDOG

n SMBus Serial Bus interface compatibility

n VID0-VID4 monitoring inputs

Key Specifications

Applications

n System Thermal and Hardware Monitoring for Servers

n Office Electronics

n Electronic Test Equipment and Instrumentation

n Voltage monitoring

n Temperature Error

n Supply Voltage Range

n Supply Current

n ADC and DAC Resolution

n Temperature Resolution

and PCs

Error

−40˚C to +125˚C

™

comparison of all monitored values

Operating:

DS100072-1

2.8V to 3.8V

www.national.com

0.4 mA (typ)

+2% (max)

3˚C (max)

June 1999

8 Bits

0.5˚C

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