Re: [SI-LIST] : IBIS Modeling

Kellee Crisafulli (
Wed, 25 Mar 1998 01:00:30 -0800

At 11:22 AM 3/24/98 -0700, D. C. Sessions wrote:
>In brief, the answer is that IBIS device models are *not* good enough.
>You absolutely need to model the substrate and the terminators (DIMM
>series resistors) on them. IBIS 3.1 includes the capability of
>defining Electrical Board Descriptions, which are basically simplified
>netlists of the PWB. The examples given are in fact memory modules.
>D. C. Sessions

We have built DIMM and SIMM module modules using IBIS 2.1 that do
a reasonable simulation job. It requires a bit of playing with the
package model and it is somewhat simulator dependant. Our simulator
large RLC package values as transmission lines instead of lumped LC parameters
which allows us to make a reasonable DIMM or SIMM module module using
IBIS 2.1 To accomplish this we create a full circuit boad model of the
DIMM or SIMM and then tweak an IBIS package model until it looks
the same under several simulation conditions. The die model input capacitance
must also be increased to account for the extra loading.

While I agree IBIS 3.x makes this relatively easy and provides a more accurate
result it is possible to get usable results with 2.1 prior to the release of
the 3.x parser.