Aug 19, 2013 · on using a 1uF X7R ceramic cap on the AREF pin of an ATMega2560, in order to be able to use its internal bandgap reference. I saw people using 0.1uF and 0.47uF. The datasheet is silent about stuff like that, as usual. The point behind having something like AREF is so you can feed it an input from a super-stable voltage source, and it will scale the A/D inputs from ground up to AREF with the full 10 bits of precision.

Looking at the datasheet for an AVR microcontroller, one can be fooled to believe that power supply is not critical. The device has a very wide voltage range, and draws only a few mA supply current. But as with all digital circuits, the supply current is an average value. The current is drawn in very short spikes on the clock edges, and if