[SI-LIST] Re: Package in IBIS Bench Files

The only package information that should matter to the I-V data, is the
resistance.  Inductance and capacitance are don't-cares, since I-V data
is DC only.

I-V data is supposed to apply to the raw die without package.  If you
can't measure that directly, then subtract the effect of the package
resistance when creating your IBIS model, to prevent double-counting.
(But double-conting the resistance is likely to reduce the ringing, not
increase it!)

If your simulations with IBIS models show such transient differences,
it's possible the RLC package parasitics used in the model are
conservative.  Or that the edge rates are too fast for the simplistic
basic package model.

IBIS says nothing about how the simulator should actually use the RLC
parameters, so the simplest thing for the simulator is to just use a
lumped model.  If your package has significant "trace" lengths, you
could get sizeable L and C values which are meaningless by themselves
because you really have a distributed structure (transmission line),
being modeled by a (probably single) lumped circuit.

You could experiment by setting the RLC values to zero in the IBIS
model, so that it represents just a bare die, then tacking on various
models of the package portion (single lumped, ladder, distributed) to
see what you get.

Regards,
Andy



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