At 12:55 AM 5/7/01 -0700, Tim Thompson wrote:
>Has anyone out there ever had hot LM7805A regulators be the cause of
>strange pic software behaviour? I have a
>PIC communicating with a program on a PC, and it was working flawlessly the
>first run, but after I reset the PIC and
>restarted the software it stoped parsing the serial data..I noticed the
>regulator was fairly hot (its trying to regulate a BAD dc output from a
>wall wart), and after letting the reulator cool the PIC ran fine..and im
>trying to see if the problem was directly the cause of the regulator being
>hot (I thought these had thermal shutdowns?)

They do, they dump your VCC, which would likely cause non-deterministic
execution.

Can you get rid of some of the load on the reg?

Then again, is there enough dissipation (calculated) for it to be hot?
Oscillating 7805's get hot, I've seen them doing a couple watts of 1-2 MHz.
That's not likely to do your CPU much good either.


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