ADC output level query
If the device is powered from 5V, the digital input levels that will work with the device are between 3.5v and 5V - that is what is said on the table on page 4.

On page 3 it quotes the digital input levels for a 2V7 supply and these are between 2V and 5V.

Please note that the digital output levels will be no higher than the power supply you feed it. If you run from a 3V3 supply then you won't get a logic output higher than 3V3 and probably more like 3V.