What is the best method for reverse voltage protection of a microcontroller
This circuit should do what you want:







simulate this circuit &ndash; Schematic created using CircuitLab

If you don't have the ability to put a series element on the negative branch, you can also implement a similar circuit using a P-FET on the positive branch instead.

N-FETs are preferable because they have lower RDSon for a given size and are also much more common parts than P-FETs.