Quote Originally Posted by Heckler View Post
@Charlie... my design is specifically designed to run on battery power. The PIC current drain should not change by much. Unless one starts trying to supply current via other pins.
Respectfully, that's simply wrong. Every different instruction uses a slightly different amount of current. Those current changes result in noise. Put a cap across the zener to resolve it. And if minimal current is your objective, you are wasting more in the zener than is used in the PIC. Use a regulator and use the PIC sleep capability to get down to minimal current. If you are really interested in parts count, have a look at some of the other PIC devices. The 12HV615 for instance - I've used this as a touch dimmer for LED lighting - can run off of 12V directly (well, through a resistor) because it has an integrated regulator. The method it uses, though, does still waste a little current.