ELM409
Versatile Debounce Circuit
Description
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.
Features
• 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
Connection Diagram
PDIP and SOIC
(top view)
V
DD
1
2
3
4
8
7
6
5
V
SS
Out
Out
In
Applications
• Pushbutton interface for logic circuits
• Limit switch monitoring
• Time delay generation
• Power on sequencing
A
B
C
Block Diagram
A
2
B
3
C
4
Control Logic
edge
detectors
pulse
generator
500 msec
debounce
In
5
7
Out
Out
6
25 msec
debounce
edge
detectors
toggle
circuit
ELM409DSA
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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