Debouncer | Cypress Semiconductor
Mechanical switches and relays tend to make and break connections for a finite time before settling down to a stable state. Within this settling time, the digital circuit can see multiple transitions as the switch contacts bounce between make or break conditions.
The Debouncer component takes an input signal from a bouncing contact and generates a clean output for digital circuits. The component will not pass the signal to the output until the predetermined period of time when the switch bouncing settles down. In this way, the circuit will respond to only one pulse generation performed by the pressing or releasing of the switch and not several state transitions caused by contact bouncing.
For more details on switch debouncing please see application note AN60024.