Re: Combining IBIS models of the same part from different vendors

Kim,

You should be very careful. Two parts may have the same data sheets, but
the edge
rates may differ by a factor of 3 or more (and signal integrity will be
correspondingly
different!).

If possible, SI should be checked using the IBIS model from each vendor
that you
use as a source for the part. At the least, check the fastest and slowest
IBIS
drivers you can encounter on each net.

It is probably safest (from a design data management perspective) to keep
the IBIS
files separate, and "sweep" the model files in the simulation tool.

-Lynne

At 03:14 PM 7/3/2001 -0700, you wrote:
>One of the difficulties in the IBIS world is: if you are using a part that
>you buy from several
>vendors, and they each give you an IBIS model for the part, how do you
>combine these
>files into some sort of composite models (assuming that is desirable at all).
>
>Now, it's easy to look at typ, min, max values for caps and voltages, and
>figure out
>what to do. Harder is combining typ, min, and max pullup and pulldowns,
>or VT curves.
>
>What I'm looking for is a "best practice" for this situation: if you've
>faced this situation, how have
>you dealt with it?
>
>Of course, maybe nobody has faced this yet, because the other difficulty,
>of course, is
>finding a part, any part, that has multiple suppliers that all provide
>IBIS models for them :-)
>But we won't go there this time!
>
>
>Kim Helliwell
>Apple Computer
>kimgh@apple.com
>408 974 9936