Yep, I've had that, and it's a fun thing to discover.  Especially when
an input to one chip causes apparently normal operation of another.

The protection diodes on inputs are there to prevent the inputs
from going above the supply rail.

Therefore, if the supply rail is unpowered, an input pin will power
it.

It is one of the reasons behind supply rail discharge clamping in
designs where the rail needs to be forced down to near zero for reset
or something.

--=20
James Cameron
http://quozl.linux.org.au/
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