Missing silicon errata ?
Alan B. Pearce email (remove spam text)
>So either I am missing something very obvious
Well, you are definitely doing that.
>OR something has indeed changed and the datasheet
>needs updating. Imho.
IMNSHO the data sheet is correct. As someone else pointed out, you are
looking at ABSOLUTE MAXIMUM ratings, NOT operating ratings.
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
See also: www.piclist.com/techref/microchip/devices.htm?key=pic
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