It could be latchup, which is when the parasitic SCR that many IC's
contain gets triggered. This usually happens if the IC has a signal on
an input pin before(and during) power is applied. It can also (rarely)
happen if an input is floating.

Capacitance from an output to ground can cause oscillation, that would
be my number 2 guess.

Cheerful regards,

Bob

On Sat, Apr 6, 2013, at 04:06 PM, veegee wrote:
> Over the past couple of weeks, I've randomly noticed on several
> occasions that some of my various ICs (MOSFET gate drivers, 74HC595,
> opamps) are getting very hot to the touch.
>=20
> I'm prototyping on a breadboard, and the power supply is a ~5V NiMH
> battery pack. For all ICs, I'm using a linear regulator and several
> decoupling capacitors around the regulator and the IC power supply pins,
> and making sure that all inputs and outputs stay within the rated
> voltage range.
>=20
> It *seems* that some of them are sometimes getting hot enough to emit a
> very slight burning smell, which I then confirm by touching the IC to
> check its temperature. There doesn't seem to be a pattern as to when
> they're getting hot. Disconnecting and reconnecting the battery pack
> seems to (at least temporarily) fix the problem.
>=20
> No switching regulators or inductors are involved. No PIC micro ever
> seems to get hot like these random ICs do. All IC high-Z inputs are
> connected to GND, and all IC low-Z outputs are either left floating or
> connected to a high-Z input elsewhere.
>=20
> Any ideas as to what could be causing this?

--=20
http://www.fastmail.fm - Accessible with your email software
                          or over the web

--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.