Greg,

Have you performed any cleanliness testing on that
board?  It sounds like you could have some
contaminants that maybe setting up a leakage path.

Joe Russeau
Precision Analytical Laboratory

--- Greg Goodenbury <[log in to unmask]> wrote:
> To TechNet Gurus:
>
>
>
> I have a circuit board that is exhibiting an
> extremely unusual problem.
> It's a basic 4 layer 1 ounce FR4 board with 7 mil
> traces/spaces.  The board
> passed CAD netlist electrical test, checks out fine
> with an ohmmeter, and
> nothing visual shows up with an x-ray.  The board
> has a 3.3 volt power
> supply which is about 2 inches away from the FPGA
> that it drives.
>
>
>
> Somehow, the voltage is being lost between the power
> supply chip and the
> FPGA.  When manually applying 3.3 volts with all
> components removed, we are
> measuring a partial voltage drop (.3 to .7 volts) on
> some pins of the FPGA
> footprint pattern that are NOT supposed to be
> connected at all.  Being that
> there are no visible shorts, and the electrical test
> didn't detect anything,
> we can't determine why we are loosing power.  Almost
> as if there was some
> kind of inductance involved, but I can't se where.
>
>
>
> We're at a loss.  Any ideas would greatly be
> appreciated.
>
>
>
> Greg Goodenbury
>
>
>
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