TLH8707

February 1993

LM1946 OverUnder Current Limit Diagnostic Circuit

General Description

The LM1946 provides the industrial or automotive system

designer with over or under current limit detection superior

to that of ordinary transistor or comparator-based circuits

Each of the five independent comparators can be used to

monitor a separate load as either an over current or under

current limit detector Two comparators monitoring a single

load can function as a current window monitor

Current is sensed by monitoring the voltage drop across the

wiring harness pc board trace or external sense resistor

that feeds the load

Provisions for compensating the user set limits for wiring

harness resistance variations over temperature and supply

voltage variations are also available

When a limit is reached in one of the comparators it turns

on its output which can drive an external LED or microproc-

essor

One side of the load can be grounded (not possible with

ordinary comparator designs) which is important for auto-

motive systems

Features

Y

Five independent comparators

Y

Capable of 20 mA per output

Y

Low power drain

Y

User set input threshold voltages

Y

Reverse battery protection

Y

60V load dump protection on supply and all inputs

Y

Y

Short circuit protection

Y

Thermal overload protection

Y

Prove-out test pin

Y

Available in plastic DIP and SO packages

Applications

Y

Lamp fault detector

Y

Motor stall detector

Y

Power supply bus monitoring

TLH8707 – 2

FIGURE 1

C1995 National Semiconductor Corporation

RRD-B30M115Printed in U S A