TLH10837

August 1990

LM2240

Programmable TimerCounter

General Description

The LM2240 Programmable TimerCounter is a monolithic

controller capable of both monostable and astable opera-

tion Monostable operation allows accurate microsecond to

five day time delays Long delays up to three years can

easily be generated by cascading two timers The timer con-

sists of a time-base oscillator programmable 8-bit counter

and control flip-flop An external resistor-capacitor (RC) net-

work sets the oscillator frequency and allows delay times

from 1 RC to 255 RC to be selected In the astable mode of

operation a single RC network sets the base frequency

The frequencies of the squarewaves at the 8 outputs are

each at different factors of 2 from the base frequency If 2 or

more of the outputs are shorted together various pulse pat-

terns can be generated These frequencies or pulse pat-

terns can also easily be synchronized to an external signal

The trigger reset and outputs are all TTL and CMOS com-

patible for easy interface with digital systems The timer’s

high accuracy and versatility in producing a wide range of

time delays makes it ideal as a direct replacement for me-

chanical or electromechanical devices

Features

Y

Accurate timing from microseconds to days

Y

Programmable delays from 1 RC to 255 RC

Y

TTL and CMOS compatible outputs

Y

Timing directly proportional to RC time constant

Y

High accuracy

Y

External sync and modulation capability

Y

Wide supply voltage range

Y

Excellent supply voltage rejection

Connection Diagram

16-Lead Molded DIP

TLH10837 – 1

Top View

See NS Package Number N16E

Order Number LM2240N

C1995 National Semiconductor Corporation

RRD-B30M115Printed in U S A