IBIS as the accurate standard.

There has been a number of emails of late about how accurate
the IBIS models. I think some of this discussion really looses
site of the FACTS.

  1) No model is "accurate" for all uses especially SPICE models.

  2) IBIS models are better than SPICE models in almost all
     respects associated with signal integrity analysis tools
     because:
      a) The model is a standard with agreed upoun rules unlike
         the 40+ different flavors of SPICE.
      b) The model is transportable as a public standard because
         it does not give away confidential design information.
      c) The models are generally plenty accurate given the
         tolerances of everything else in the system. e.g.
         PCB tolerences, IC process tolerence, power supply,
         etc.. Do we really need 5% accuracy when the
         IC varies by factors of 2 in some cases. The PCB's
         alone can make impedance changes of 10% or more.

 3) IBIS models can be made from measured data or translated
    from SPICE model data. This makes them much more flexibly
    constructed then SPICE models.

BOTTOM LINE:
IBIS models are accurate enough for today's signal integrity
needs in 99% of the cases.

best wishes to all,
Kellee

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Have a great day...Kellee Crisafulli, HyperLynx Inc.
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Received on Tue Oct 29 12:42:49 1996