LM79 datasheet(1/31 Pages) NSC

部件名	LM79

功能描述	Microprocessor System Hardware Monitor

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制造商	NSC [National Semiconductor (TI)]

网页	http://www.national.com

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LM79

Microprocessor System Hardware Monitor

General Description

The LM79 is a highly integrated Data Acquisition system for

hardware monitoring of servers, Personal Computers, or

virtually any microprocessor based system. In a PC, the

LM79 can be used to monitor power supply voltages, tem-

peratures, and fan speeds. Actual values for these inputs

can be read at any time, and programmable WATCHDOG

limits in the LM79 activate a fully programmable and

maskable interrupt system with two outputs.

The LM79 has an on-chip temperature sensor, 5 positive

analog inputs, two inverting inputs (for monitoring negative

voltages), and an 8-bit ADC. An input is provided for the

overtemperature outputs of additional temperature sensors

and this is linked to the interrupt system. The LM79 provides

inputs for three fan tachometer outputs. Additional inputs are

provided for Chassis Intrusion detection circuits, 5 VID moni-

tor inputs, and chainable interrupt. The LM79 provides both

ISA and Serial Bus interfaces. A 32-byte auto-increment

RAM is provided for POST (Power On Self Test) code stor-

age.

Compared to the LM78, the LM79 has the following differ-

ences:

•

an additional VID input pin

•

an additional register for device identification

•

open drain Power Switch Bypass Output

Features

n

Temperature sensing

n

5 positive voltage inputs

n

2 op amps for negative voltage monitoring

n

3 fan speed monitoring inputs

n

Input for additional temperature sensors

n

Chassis Intrusion Detector input

n

WATCHDOG comparison of all monitored values

n

POST code storage RAM

n

ISA and I

2C™ Serial Bus interfaces

Key Specifications

j Voltage monitoring

accuracy

±1% (max)

j Temperature Accuracy

−10˚C to +100˚C

±3˚C (max)

j Supply Voltage

5V

j Supply Current

Operating:

1 mA typ

Shutdown:

10 µA typ

j ADC Resolution

8 Bits

Applications

n

System Hardware Monitoring for Servers and PCs

n

Office Electronics

n

Electronic Test Equipment and Instrumentation

Ordering Information

Temperature Range

Package

−10˚C

≤ T

A ≤ +100˚C

Order Number

Device Marking

LM79CCVF

VGZ44A

# Indicates Active Low (“Not”)

Connection Diagram

I2C® is a registered trademark of the Phillips Corporation.

DS100036-2

February 2000

DS100036

www.national.com

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