jamz-az/PIC18F-Dev — Issue #2: 18F4620 ADC
Author: jamz-az
Created: 2012-01-18 02:48:55+00:00
State: open

ADC is very noisy on this PIC.
I have tried all the usual things like; (and many more)

Sleep during adc conversion
ADC Tad increases
Fosc / xx (all off them)
Doing means on over 10-50 samples.
Enabling/disabling all analog inputs one by one on the fly.
Caps on all analog inputs for smoothing.
I have a very clean pcb and great ground planes.
Everything is decoupled properly.

It is my conclusion that the adc on the 18F4620 is too noisey to use for any real calculations if you want accurracy.

I get at best +-2 values or digits flop on adc converts.

Doing temperatures or pressure sensing it is not accurate enough and fails.

All my other projects on 16F's do not show this issue at all and are very stable doing adc on many ext sources like temp pressure etc.