> It looks PIC16F946 has separately supplies pins for AD.
> If this is true, AVss should be connected directly to the supply (in
> the same point Vss is connected). Avdd could be supplied from a
> separate clean  supply or from an
> LC filter connected directly to Vdd. If the environement is clean,
> AVdd and Vdd could be supplied together from the same power supply.
you could just tie them together but doing so would not be the best thing from a noise perspective.

if you want best performance the analog and digital grounds in your cuircuit should be connected together at one point only and there should be a filter between the analog and digital power supplies.

pic adcs are iirc only 10 bit though anyway so it may be that this doesn't gain you much if you already have good decoupling on the power supply


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