[sdiy] Sudden IC death?

Karl Ekdahl elektrodwarf at yahoo.se
Mon Sep 20 16:17:06 CEST 2010


> Yes, it is possible for static
> discharge to cause this sort of failure. Was the environment
> very dry there? Why was the case open rather than closed? 
> Over voltage applied to the chip, either through power
> supply or signal lines, or shorting of high currents through
> the switches could also be a cause. 

I'm not sure how humid it is here - 57% today, is that much? The case is a  standard euro-rack without top or bottom lids (as they usually are). I didn't ever see any weirdness in the PSU voltages..

> Check the circuit includes adequate current limiting
> resistors, bypass capacitors, clamping diodes etc around
> these chips. Or perhaps you just got a bad 
> batch.... 

The strange thing is that it all worked through all the various tests i did, and this on several different occasions.

> The only thing I can think of that
> would kill them ALL at the one time, is a
> spike on the power rail (or on ground).
> 
> Unless the circuit is strange ..
> 
> What is the normal power voltage across the chip in the
> circuit?

I guess a power-spike is possible, i did notice that another board in the same unit had its ground-cable disconnected by mistake. The ICs use +5V so it's not like i'm puttin a lot of stress on them.

Oh well i guess i'll see today if it fries itself again once i go to install it in a few hours...

Karl 





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