The notification service tells me a new app note has been posted:
AVR125: ADC of tinyAVR in Single Ended Mode Application Note
I read it over, and am curious about this title and subject. I can find nothing that wouldn't apply directly to e.g. Mega88.
Most of the text explaining the ADC seems to be right out of the datasheets.
There is one interesting tidbit, that is in the section on doing a conversion to measure the bandgap. As a high-impedance source, the recommendation is to run a few conversions against the 0V/Gnd channel to drain the sample-and-hold, and then run conversion(s) on the bandgap.
...configure 0V (GND) in ADC by setting Mux bitfield (MUX3:0) equal to 1111. This is done to discharge the capacitor of ADC
"¢ After 70ÂµS, measure the bandgap reference value by configuring Mux bitfield (MUX3:0) equal to 1110. It should be measured after 70ÂµS delay, because of the time taken to charge the capacitor of ADC