I am using the ADC of the PIC16F18344 —
It has neither Avdd nor Agnd, but it does have selectable Vref+ and Vref- pins. If I were to stop using chip Vdd and Vss for ADC, dedicate a regulator to Avdd and Avss, run these lines to the Vref pins, and select them in the firmware, would I see accuracy benefits equivalent to a device that had dedicated analogue supply pins? I think, for this application, noise immunity is more important than absolute accuracy. There is also calibration supported, as well.
Currently the ADC is connected in simple voltage divider/"ratiometric" configuration with a rheostat:
I am using all 10 bits of the result, although I can tolerate some error in the least-significant bits. I am using a software median filter to cancel noise and it works fairly well. The sampling rate is quite low, perhaps two or three times a second. There is a passive T filter before the ADC; the chokes are actually approximations of ferrite cores.