LM81 datasheet(1/32 Pages) NSC

部件名	LM81

功能描述	Serial Interface ACPI-Compatible Microprocessor System

PDF	32 Pages

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制造商	NSC [National Semiconductor (TI)]

网页	http://www.national.com

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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™ limits in the

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, witha0to 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

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

supplies directly

n 8-bit DAC output for controlling fan speed

n 2 fan speed monitoring inputs

n Chassis Intrusion Detector input

n WATCHDOG™ comparison of all monitored values

n SMBus Serial Bus interface compatibility

n VID0-VID4 monitoring inputs

Key Specifications

n Voltage monitoring

Error

+2% (max)

n Temperature Error

−40˚C to +125˚C

± 3˚C (max)

n Supply Voltage Range

2.8V to 3.8V

n Supply Current

Operating:

0.4 mA (typ)

n ADC and DAC Resolution

8 Bits

n Temperature Resolution

0.5˚C

Applications

n System Thermal and Hardware Monitoring for Servers

and PCs

n Office Electronics

n Electronic Test Equipment and Instrumentation

Typical Application

TRI-STATE® is a registered trademark of National Semiconductor Corporation.

WATCHDOG™ is a trademark of National Semiconductor Corporation.

SMBus™ is a trademark of the Intel Corporation.

DS100072-1

# Indicates Active Low (“Not”)

June 1999

DS100072

www.national.com

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