3.3V and 5V on a single board

I started designing a new board for Alarm security system today, It would be having components that would be running on 3.3V and some at 5V. Although I can power micro-controller by 3.3V, but still I would require it to run at higher frequency, and Max485 wont work on something very close to 3.3V, not even at 3.9V. So I browsed some forums to check what are the best approaches and came across this document called 3V Tips ‘n Tricks by Microchip. Its so useful that I wished to share it here.



3V TIPS  AND TRICKS (mirror on dms)

The Complete Book: