Tiny IC Debounces Pushbutton Switch
The internal one-shot provides an instant response to the first falling edge on the input and then delays any further response until 140msec after the last rising edge. The MAX812 shown inverts the pushbutton input; a similar device (MAX811) is noninverting. The ICs also incorporate a power-on reset function that asserts the reset output when VCC falls below a preset threshold and also asserts the output for 140msec after each application of power. Selecting an R-suffix part sets this threshold at its lowest value (2.63V), preventing false outputs in the debouncer except when the supply voltage fails.
Using almost no real estate, this circuit squares up and debounces a pushbutton signal and extends it to at least 140msec.
A similar version of this article appeared in the April 1, 2001 issue of EDN.