pic microcontroller discussion list wrote:
>> I call it the fool's diode. Is that enough to
>> explain its function?
>
> Nope
>
> Me fool ...
>

it's for reverse-polarity protection. When power and
ground are applied correctly, the diode is reverse
biased and not conducting.

when power and ground are reversed, the diode is
forward biased and conducts; the voltage is limited
to one forward diode drop (varies with diode, current
and temperature, but you usually assume 0.7V for a
rough estimate)

a problem occurs if the power supply can supply more
current than the diode can handle, then something will
start to smoke.

Ideally a fuse is added. The idea is that if the
diode conducts, it blows the fuse before anything
else is damaged.


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