>
> > The clamping diodes are useful when working with large input voltages
> > needing only an external current limiting resistor for this purpose.
> >
>
>This comment is likely to reignite a religious war here on PICLIST. There
>are those that state that you must have more than a simple series resistor.
>Others claim that this technique is valid.

Most devices have similar clamping diodes.
The problem is that most manufacturers won't specify how much current you
can put into a pin in this manner. So, if you end up depending on this,
you're into a grey area as far as a dependable production design.

If you get it wrong, you risk SCR latchup on the die, and the only way out
is to power down, and let the device cool. (assuming it hasn't been toasted)

>2: in the dc parameters the maximum current is limited to (for some typical
>chips) 20 ma.

Output current rating, not related to how much you can safely dump through
the protection diodes.


Why is it though, that the PIC line seems to have so many exceptions,
gotchas, and "features"?


--
Dave's Engineering Page: http://www.dvanhorn.org

I would have a link to http://www.findu.com/cgi-bin/find.cgi?KC6ETE-9 here
in my signature line, but due to the inability of sysadmins at TELOCITY to
differentiate a signature line from the text of an email, I am forbidden to
have it.

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