AVR-Chat

>
> > If there isn't enough load to pull that current back out of the rail,
> you
> > end up raising the 3.3V rail out of spec.
>
> Latchup only happens over a certain thresh-hold, so if you're confident
> that your overdrive is always much lower than that, then problem solved.


I'm not willing to generalize the behaviour of an unpublished parameter
across large numbers of chips from a small sample, especially when the
variability of that parameter is unknown.

Also, what do you do about the current you're dumping into the 3V system?

I saw something like this happen on a 5V system where the incoming current
was enough to shut down the output of the 5V regulator, and raise VCC to
5.24V.  While this SEEMED to be barely within tolerance, the systems
suffered from unpredictable crashes.  Eliminating the source of the excess
current into VCC solved the problem.
In this case, the current into VCC was coming through the protection diodes
on a ULN2003, which are rated for some fair current, and the problems were
not latchup related.


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