[sdiy] Sudden IC death?

[ASSI]

On Monday 20 September 2010, Karl Ekdahl wrote:
> So i'm doing this sound installation and when i was to install my piece
> it didn't work, turns out that *all* of the 74HC4066's in my circuit had
> blown for no apparent reason - so i'm just wondering, what would do
> this? The whole thing stayed in it's (open) case all the time, i didn't
> rub it in cats or anything but my only guess is some weird static
> electricity shock?

About the only thing (aside from a gross overvoltage which would likely show 
up in other places as well) that I can think of that would take them out all 
at once is external latchup, i.e. the power supply doesn't do what it 
supposed to do and you actually supply the IC from one of the output pins.  
A CMOS part used in this way actually is a thyristor that will trigger at 
some current and go into low-impedance state.  If the current is not limited 
or power removed _very_ quickly, the part will burn out in no time (often 
the package explodes or the parts de-solder themselves - quite a sight if 
you do it on purpose).  So if you happened to have ground or V+ missing in 
part of the circuit but not in others and you didn't have series resistors 
in the ouptut lines to limit current, that might have done it.


Achim.
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