piclist-bounces@mit.edu wrote:
> The current rating for the diodes allows static discharge
> during handling - not current while operating. These diodes
> are not specific components put there for the purpose you are
> attempting to use them for, but intrinsic to the
> manufacturing process, and made to have specific
> characteristics that allow them to become protection against
> static charges during handling. As such they have connections
> to "funny places" elsewhere in the chip substrate, and as you
> observe, when the diode conducts it does other funny things
> to the circuit which stops it working.
> 
> In short, despite other chips "apparently" working correctly,
> you cannot rely on this, and must use an external schottky
> diode to protect the input and stop the internal diode from
> conducting. Your talk of using a more expensive component to
> protect a cheap microprocessor is not an uncommon occurrence.

That's a nice explanation. This topic should probably be part of a FAQ.

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