ELM409 View Datasheet(PDF) - Elm Electronics
Part Name
Description
Manufacturer
ELM409 Datasheet PDF : 8 Pages
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ELM409 Operation
The circuit of Figure 4 shows how the ELM409
would typically be connected to debounce the signal of
Figure 1. Other than powering the ELM409, all that is
needed is to connect the options pins (A, B and C) to
VSS (providing low levels on all three), connect the
noisy switch signal to the input pin, and then connect
the ELM409 output pin to the digital circuit.
The output of the ELM409 in Figure 4 would
appear as shown in the ‘scope traces of Figures 2 and
3 (the lower traces). There is a slight delay (25 msec)
due to the debounce period, but otherwise, the signal
appears as you would expect from an ‘ideal’ switch.
The ELM409 is capable of performing several
other functions on the input signal - it can do more that
just debounce the signal. For example, it can provide
a change in output on the signal edges (transitions
from a low to a high level, or from a high to a low
level), and it can alternate (toggle) the output on each
occurrence of an edge. Each of these possibilities are
selected by changing the logic levels at the A, B and C
pins. The eight combinations are described in Table 1
below, and also appear pictorially on the next page.
ELM409
4321
409
5678
Digital
Circuit
Figure 4. Debouncing the pushbutton
Function
Follows
Input
Pulse on
Rising Edge
Pulse on
Falling Edge
Toggle
on Edge
A B C Debounce Period
Notes
000
25 msec
Standard contact debounce
001
500 msec
For very noisy circuits
010
25 msec
Output pulse is 50 msec wide
011
500 msec
Output pulse is 50 msec wide
100
25 msec
Output pulse is 50 msec wide
101
500 msec
Output pulse is 50 msec wide
110
25 msec
Changes on input H -> L
111
25 msec
Changes on input L -> H
Table 1. ELM409 options
ELM409DSA
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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