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Re: Source for Sony SBX1602A Serial to Parallel chip??



>Does the chip suck, or is it a circuit design problem?


If you think about it, unless the integrated circuit design is botched
badly, I.C.'s are not capable of destroying themselves.  I'll stick my neck
out and say that most I.C. failures should be traceable to external factors
(design, environment, utilization):  heat, static discharge, bad power,
sledge-hammers, Coca-Cola, etc.

I can think of a few examples:

The first is static discharge damage.  This failure mechanism is generally
characterized by a "delayed reaction".  Static damage can be "soft" damage
that will make the chip fail days, weeks, even months or years after the
zapping event.  Static discharge is also cumulative:  more zapping makes it
worst and alters the ultimate failure mode. This, obviously, is not a design
problem as much as it is a materials-handling issue.
Be careful in your handling of circuit boards, you might be inducing random
failures.

A more obscure "soft damage" case is that of an inappropriate soldering
profile, particularly with surface-mount components.  This kind of
failure --very rare-- might not cause a sub-assembly failure for a long,
long time.

Another good example of hidden failure mechanisms is the case of driving
MOSFET's beyond their full enhancement zone.  They will work and, generally
speaking, they will be more efficient than if one stayed within the normal
enhancement region.  However, this sort of design liberty will probably lead
to premature or random failures.  This, of course, is a design problem.
Power supply noise and spikes can make this happen.

CMOS and other integrated circuits use a MOSFET push-pull output topology
(even in internal interconnects).  High operating temperatures and other
factors can cause switching cross-conduction (also known as shot-through
current) that will, at the very least, cause soft damage and overheating of
the semiconductor and, at worst, sudden and catastrophic failure of the
device.
Keeping circuit boards cool is very important.

These are just a few examples of how a design engineer can "design-in" a
reliability problem.

I guess that what I am trying to say is that, before I believe that Sony is
making bad chips by the hundreds, I would point my finger at the circuit,
board or product in which they are used.  I'll bet most failures are due to
designs violating Sony's own ratings and/or common-sense design rules.


-Martin Euredjian
 Telecine Engineer
 Todd AO / Hollywood Digital
 martin at hollydig.com
 martinfx at msn.com



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