Hi..
Due to low information, I assume that you want to measure
a high AC voltage (Lets say 220V) with ADC.
By my experience, it is possible to do it with very low
number of componments:
Take a large resistor, lets say 500K, and 5K (For example)
connect them serial, And congratulations...
you have voltage divider, which you can connect it to the
ADC input, and it'll divide the 220VAC by about 100
(i think. no time for calculations.) so you'd have A Sinus
AC Of 2.2V

Goodluck
OK


Hope its helpful