What is the Atmega8 input impedance. I want to add a push button to an Atmega8 and my configuration would look something like this:
A +5V source, resistor, push button not pressed goes to Atmega8, pushed goes to ground.
From my understanding Atmega8 is a CMOS and therefor the input impedance would be very large, most likely in the 100MOhm. For a logical high the Amtega8 need 0.6Vcc, my Vcc is 5V, therefore a high will be considered for anything above 3V. Assuming that my assumption of very high input impedance is right, the resistor can be:
3V = 5*100M/(100M+R) ==>R = (500-300)/3 = 66.66MOhm.
Would that be the correct theoretical highest resistor value that I can use?
**The actual resistor used will be a 47kOhm but I really want to know how to find the maximum theoretical value.