Schmitt trigger input high 3V threshold and input low 0.1V threshhold or other chip?

Question

Are there any chips similar to a Schmitt trigger but with a wider high low input threshold that trigger high with 3-3.3V and low 0.1-0.2V?

I need it to alleviate switch bounce.

A comment from the Teensy forum:

You want to get it below 1.15 to be sure it reads as low, and above 2.31 to be sure it reads as high. The actual threshold is somewhere between those two, with approx 60 mA hysteresis.

I looked and I saw a circuit that can be made with an op amp. I want to know if there is a chip similar to a Schmitt trigger. Simple input-output and many inputs/outputs.

Answer 1

No, there is no Schmitt trigger device that evaluates >3V to high and <0,2V to low. A Schmitt trigger is nothing else than an amplifier with positive feedback loop so you can build your circuit like that:

^{simulate this circuit – Schematic created using CircuitLab}

The problem can also be solved with an operational amplifier, but it makes more sense to use the 4069 hex inverter.

The Hysteresis is calculated as follows: $$ Hysteresis_{} = \frac{R_1}{R_2} $$ R2 must be larger than R1. with almost equal resistors you can achieve almost 100% Hysteresis and with a R2>>R1 basically 0

e.g.: 3,3V logic R1=100k; R2=120k the Hysteresis is 0,83, the lower Voltage is ~0,11V and the upper Voltage is ~1,93.

Debouncing requires a low pass filter before Schmitt trigger input. I made good experiences with 10nF and 51kOhms. My mechanical switches bounce back and forth for about 1ms, and I found 0,5τ to 1τ perfect for debouncing.