I want to say that is good advice, but doesn't line regulation on a 7805 not kick in until 7 volts input? I've never actually tried to use a linear voltage regulator that far below its rated input.
Good point for...
I am starting a design that needs to run on a very unregulated power supply. Arcade systems for those that are interested. Voltage can vary quite a bit, so it would be good if the microcontroller could survive 5.4v or...