A/D Conversion Clock Select bits confussion ..

[aratti]

The 11 TADs is the time taken by the MCU for the 10 bits convertion! Please do not confuse acquisition with convertion. The setting suggested is the time you will give to the sample & hold capacitor to charge with your input dc value. This time should be enough to charge the cap not beyond the 1T, because beyond this point the charging function is no longer quasi-linear, but totaly logaritmic.

You can set it to 20 us and see If your ADC reading are consistent and adjust this value to suite your need. (Remember that the best acquisition time will depend by the hardware setting, so every circuit has his own best acquisition time)

Cheers
Al.