Hi Guys and Dolls,
I've been searching the fora a bit and could not find anything to the following observation. If it is a problem that needs to be resolved remains to be seen...
While playing with an Atmega168 I found the output of several pins a bit noisy. Humm... Lets zoom in. Ripple noise found of 320 mV at 5V output. Frequency around 38.5 MHz (twice the freq of the xtal). I want to get rid of the noise without filtering the output.
Q: why is this noise here in the first place
Q: How to get rid of it
Q: Is it a fundamental design fault?
A 100 muH inductor is in the Vcc line with proper condensators.
I found out if one does NOT put 5V to the AVcc, the chip is not working - but if one has a floating Vcc (+ +5V to AVcc) the chip is still running its code - with a reduced ouput voltage.