The Atmega datasheets recommend a LC filter for the AVCC (analog power) pin. None of the Arduino schematics seem to implement this. Was there any research into just what those parts might buy in terms of noise reduction on the analog pins? Some of the Atmel boards out there seem to use the filter, and others, similar to Arduino, ignore the issue. I've also seen RC filters used. I dug through the datasheet a bit and didn't find an input impedance for the AVCC pin, anyone have info on that?
Anyone on the Arduino hardware side have any insight here?