Am using adafruit (American hobbyist electronics components retailer) breakout for the max31850 thermocouple amplifier who's data line isn't 5v tolerant. Therefore I want to power my atmega328P @ 12mhz 3.3v. I have been told this is the optimum speed for a 3.3v power rail.
THe lcd am using to display the temperature is unfortunately a 5v lcd I believe since I tried powering it from 3.3v it didn't even light up. I used a commercial bench supply @ our lab to test this. As soon as I upped the voltage to 5v it lit up the first row. My question is will the 5v on the lcd cause damage to the atmega? MY understanding is current always flows towards lower potential. The difference in voltage can cause a large current to flow right?