Cleaner ADC measurements which of these ways is better

Other Hardware General Electronics
6

MarkT:
If you feed a different voltage into AREF you need to call analogReference(EXTERNAL); in
setup() before using the ADC, to prevent the internal linking of AREF to Vcc.

3.4V to 3.3V is a very small voltage drop, I would suggest just filtering the 3.4V heavily, rather than
expecting a linear regulator to perform well with 100mV of dropout. Perhaps RCRC filter to AREF.

I'm not using arduino for this, but of-course once Aref has external voltage Vcc and V1.1 leave this equation.
I am planning to use mic94310 as a LDO, it has 100mA drop out voltage max at 200mA, should be ok.
Never actually came across RCRC filter, sounds very interesting, thanks for pointing out, researching now.