I'm trying to make a small module that has 2 rotary encoders (both have build-in push buttons), hardware debouncing circuit and have to be compatible with both 5.0V and 3.3V microcontroller logic inputs.

What I've found, that most typical schematic involves the inverting Schmitt trigger (74HC14 or 74LS14) and should be looks like:


simulate this circuit – Schematic created using CircuitLab

The D1 could be omitted since it is just for decreasing charging time of capacitor C1.

Could you help me with questions:

1) Will 74HC14 (74LS14) work with 3.3V input?

2) Could 74HC14 (74LS14) use the 3.3V as power supply?

3) Could 74HC14 (74LS14) produce the 3.3V output to be connected with STM32F103**** (or other 3.3V logic level microcontoller)

Or should I use the SN74LV14A instead of 74HC14 (74LS14)? Looks like SN74LV14A is more suitable for lower voltages.


1 Answer 1


You want the 74HC14. The HC series will operate at your 3.3 Vcc. The LS will not.

For your questions 1-3, yes to all for the HC series.


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