Arduino with programmable Aref voltage

[tuxstef]

Dear Arduino developer team,

as I found out, that the avr's implemented switching of the AVCC voltage to the internal Aref connection seems to be imprecise (variation >= 3 bits), I suggest a circuit like the one on the Atmel STK500 board.
A LTSpice simulation was performed to verify the adaptions being made.
Further, another approach was designed to ensure the correctness of the ADC readings for another project.

The modified PWM Aref voltage generation:

The second variant using a common I/O pin of the Arduino (Micro):

Hopefully, you may implement something like these.

Yours,
Stefan