RE: [IBIS-Users] IBIS model check

Can you look at the VI data and tell if it makes sense?  Some (maybe
most) of the problems I've had recently have been problems in the SPICE
model.  The IBIS data mapped to the SPICE deck just fine.  But I knew
that the transistors just wouldn't do what the curves said.  They had to
fix the SPICE model before re-doing the IBIS model.

Aubrey Sparkman 
Enterprise Engineering Signal Integrity Team
Dell, Inc. 
Aubrey_Sparkman@Dell.com 
(512) 723-3592

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of Andrew Ingraham
Sent: Wednesday, August 17, 2005 2:19 PM
To: Indira Gazula
Cc: ibis-users@eda.org
Subject: Re: [IBIS-Users] IBIS model check

> So effectively, in the absence of either spice curves or measurement 
> data, I'm stuck with no way of verifying the IBIS model?

The same is true of SPICE models.

You can run experiments like you did to see how it compares with the
published spec sheets (which is really just a quick "sanity check"), but
a better "proof" would be to compare it with measured data from actual
parts.
If you have access to such data, you can compare either in the static
(i-v) domain, the time domain, or hopefully both.

With the experiment you did, make sure the toggle rate is low enough so
you weren't hitting some sort of resonance, which might have made the
amplitude appear larger than normal.

I have seen some "interesting" models from time to time, both SPICE and
IBIS, that did not represent reality.  It's always good to question what
you have.

Regards,
Andy


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