ELM411
Debounce Circuit with Latch
Description
The ELM411 provides all of the necessary
circuitry to connect as many as three independent
mechanical contacts to an electronic circuit.
All mechanical contacts, whether from switches,
relays, etc. will have inherent ‘bounce’ when they
make or break a connection. Depending on the type
of switch, this fluctuation can be quite pronounced,
often being interpreted as multiple inputs by high
speed digital circuits.
All of the logic required to remove the bounce
from most mechanical sources is provided by this
circuit, without the use of additional components. As
well, internal pull-up resistors have been provided so
that the switch inputs can be directly connected to
the 8 pin package.
The ELM411 is composed of two separate
inverters which follow the input directly, and one
latch circuit which toggles its state each time a
closed circuit is detected on the input.
Features
• Low power CMOS design - typically 1mA at 5V
• Wide supply range - 3.0 to 5.5 volt operation
• Simultaneous monitoring of three circuits
• Full 25msec debounce period on contact closure
and opening, without external components
• Internal pullup resistors for contact monitoring
• High current drive outputs - up to 25 mA
• Can be cascaded to provide sequential outputs
Connection Diagram
PDIP and SOIC
(top view)
V
DD
Out1
1
2
3
4
8
7
6
5
V
SS
In1
In2
Out3
Applications
• Pushbutton interface for logic circuits
• Limit switch monitoring
• Time delay generation
Out2
In3
Block Diagram
V
DD
Out1
2
Debounce
Timers
V
DD
7
In1
Out2
3
Debounce
Timers
V
DD
6
In2
In3
4
Debounce
Timers
Toggle
Flip-Flop
5
Out3
ELM411DSB
Elm Electronics – Circuits for the Hobbyist
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