RE: [IBIS] C_comp in IBIS


Subject: RE: [IBIS] C_comp in IBIS
From: Ken Kirschner (kenk@cadence.com)
Date: Wed Mar 06 2002 - 12:20:28 PST


Jason,
        Todd Westerhoff had a thread on the Si list related to this. It starts with
meassage #1930.

Ken

-----Original Message-----
From: Pritchard, Jason [mailto:jasonp@tenornetworks.com]
Sent: Wednesday, March 06, 2002 2:40 PM
To: ibis@eda.org; si-list@freelists.org
Subject: [IBIS] C_comp in IBIS

Hello all-

When creating an IBIS model from spice, the output rising and falling
waveforms include the device i/o capacitance (c_comp). If this is a
BI-directional model you would include C_comp to model the input capacitance
and end up double counting the capacitance on the output. Is it neccessary
to somehow isolate the output capacitance when creating the rising and
falling waveforms?

I found this note in the IBIS document:
"All tables assume that the die capacitance is included.
Potential numerical problems associated with processing the
data using the effective C_comp for effective die capacitance
may be handled differently among simulators."

What is happening here? What does XTK do for example?

Thanks,
-Jason
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