Elm Electronics – Circuits for the Hobbyist

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Connection Diagram

PDIP and SOIC

(top view)

1

2

3

4

8

7

6

5

Versatile Debounce Circuit

The ELM409 is digital filter circuit that is used to

interface mechanical contacts to electronic circuits.

All mechanical contacts, whether from switches,

relays, etc. will have inherent ‘bounce’ when they

make or break a connection. When that contact is

used for the electrical input to a digital circuit, the

bounces can easily be incorrectly interpreted as

multiple inputs. The ELM409 contains all of the logic

that is typically required to remove the bounce from

such signals, and provide a signal that has only one

transition.

In addition to providing the standard debounce

function, the ELM409 may also be configured for

other useful functions such as generating pulses or

alternating output levels on signal transitions.

No external components are needed for the

operation of the ELM409, as all timing and logic

functions are performed internally.

• Standard and extra long debounce times

• Schmitt input provides hysteresis

• Complementary circuit outputs

• Needs no external timing components

• Low power CMOS design - typically 1 mA at 5V

• Wide supply range - 3.0 to 5.5 volt operation

• High current drive outputs

• Pushbutton interface for logic circuits

• Limit switch monitoring

• Time delay generation

• Power on sequencing

In

Out

A

Description

Applications

Block Diagram

1 of 8

Features

ELM409DSA

B

C

ELM409

Out

6

7

5

In

Out

500 msec

debounce

2

3

4

C

A

B

Control Logic

Out

25 msec

debounce

edge

detectors

edge

detectors

pulse

generator

toggle

circuit