Quote Originally Posted by Acetronics
Just compare a 2.5v ref ( or a Zener !!! ) to Vdd ( through a res. divider ...) and comparators will work fine here !!!
Alain,

That is exactly what I meant in my post by "additional efforts." I did not want to go through the formal explanation if Charudatt was doing something different (which still is not clear to me from his/her posts). If it were me, I would ADC measure a reverse Zener or forward LED voltage. When the ADC value rose to a cutoff level (because the Vdd would be decreasing), I would flash the LED. You also could use the internal comparator in a similar manner. However, the specifics depend on whether or not Charudatt is using a regulator, anticipated temperature conditions, the problem Charudatt is trying to solve, etc. - I was looking for more input before providing more options. I think we match on how we would solve the scenario asked in my earlier reply. Now charudatt has lots of options.

Charudatt, please let us know how it turns out.

Paul Borgmeier
Salt Lake City, Utah
USA