Hi Rob,

Most of the drudgery has already been taken care of by Cygnal's applications engineers. Read their application notes on 5V systems (AN011) and ADC settling time (AN019). My experiences in using Cygnal devices in mixed-voltage systems have been absolutely painless and I expect that you won't have any major problems either. I you do run into trouble, you can take full advantage of their user forum.

Good luck with your projects,

Rob.