How long does a Bourns/74HC14 debounce filter take

[Demon]

From my observations, it takes 93usec for a signal to travel through a Bourns debounce filter and a 74HC14 Schmitt Trigger.

9735

(my eyes just gloss over when I try to figure this out from a datasheet :D )

[richard]

tor = RC [rc time constant]

falling tor = 10k*0.1uF = 1mS
smit trigger will definitely be triggered @ tor*2 = 2 mS


rising tor = 20k*0.1uF = 2mS
smit trigger will definitely be triggered @ tor*2 = 4 mS

9736

[Demon]

I'm using 10K - 0.01uF, exactly like here:

9737


Along with Toshiba's TC74HC14AP Schmitt trigger (I'm guessing I'm supposed to look at propagation delay ? ):

https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/1134/TC74HC14.pdf


My math uses fuzzy logic at the best of times. :D

[richard]

I'm guessing I'm supposed to look at propagation delay ?\

propagation delay has virtually zero impact on the debounce time


tor = RC [rc time constant] is the most significant factor by 3 orders of magnitude

falling tor = 10k*0.01uF = 100uS
propagation delay 0.021 uS

debounce time is the time taken for the st input voltage to fall from vcc to the
Negative threshold voltage for the SCHMITT trigger ie 2*tor

rising tor = 20k*0.01uF = 200uS


debounce time is the time taken for the st input voltage to rise from ground to the Positive threshold voltage for the SCHMITT trigger ie 2*tor