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Switch Debouncer with Only One Inverter

2014-12-03 22:03  
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Figure 1 

This circuit acts as a debouncer that prevents multiple logic signal transmitting when a switch is pressed. It takes its logic power from only the remote pull-up resistor R2 and can be used in non-energized devices such as a device in a system that’s just coming from the stand-by.

When the S1 button is at the release position, C1 capacitor is charged and keeps the inverter (7z04 – Ultra High Speed Inverter) input at a high state so the output of the inverter is low. Since the inverter output is already connected to the ground, it draws no current – consumes no power. In this situation, the output Vout keeps its state at high.

When the S1 button is pressed, C1 discharges and the state of the input of the inverter changes to low so the output of the inverter goes high and the IC starts to conduct heavily. As a result, Vout becomes low until R1 charges C1 to drive IC again towards Vss. When the capacitor charges sufficiently enough, IC stops driving current and Vout returns to a high state.

D1, D2 and D3 diodes are in conjunction with R3 to shift the level of Vout for improved compatibility withCMOSgate.

Source: http://www.edn.com/index.asp?layout=article&articleid=CA217664

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