more on protection diodes
Jim Hartmann email (remove spam text)
A while back I reported that very small currents (<10uA) "into" the upper
protection diode on an input caused the PIC to draw more current into VDD.
Recently I have found that current "out of" the lower protection diode
causes more severe problems. Currents of about 2mA on the 16C622 can cause
registers within the chip to change or can cause a chip reset (possibly
watchdog). When pulling current out of a PORT B input, I observed
spontaneous changes to TRISB and OPTION registers as well as reset.
So I guess the moral is to be *very* careful about using the input
protection diodes as clamps for inputs.
See also: www.piclist.com/techref/index.htm?key=more+protection
You must be a member of the
piclist mailing list
(not only a www.piclist.com member) to post to the