[IBIS-Users] RE: [SI-LIST] Which package model is more useful and practical?

Eric,

There is another good reason to use distributed package modeling (.pkg) data
with IBIS - if the edge rates are fast enough, and the package is large
enough, the ability to represent the package parasitics with a lumped model
breaks down.

This is just the traditional tranmission line rule as it applies to
packages. You can compute the value of the delay from the lumped package
model [Td=sqrt(LC)] and compare it to the expected signal edge rate. That
should tell you whether a lumped package model will suffice, or you need to
consider a transmission line style package description instead.
Microprocessors, FPGAs, ASICs and other large package devices tend to fall
into this category.

As an aside, having the .pkg data reside in the IBIS file itself (as opposed
to an external .pkg file) makes for one less piece of data for the user to
manage (and one less piece of data to misplace...).

Hope that helps,

Todd.

Todd Westerhoff
High Speed Design Specialist
Cisco Systems
1414 Massachusetts Ave - Boxboro, MA - 01719
email:twesterh@cisco.com
ph: 978-936-2149
============================================

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 You raise me up, to walk on stormy seas;
 I am strong, when I am on your shoulders;
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-----Original Message-----
From: si-list-bounce@freelists.org
[mailto:si-list-bounce@freelists.org]On Behalf Of Eric Hsu
Sent: Thursday, March 11, 2004 7:06 PM
To: Ibis-Users (E-mail); Si-List (E-mail)
Cc: Frank Dunlap
Subject: [SI-LIST] Which package model is more useful and practical?

Hi Expert,

  Has anyone ever really used *.pkg with IBIS model to do some =
simulation, such as SSN? If so, can anyone let me know what's benefit we =
can get from it? Myself prefer choosing IBIS model with package data for =
pin R/L/C from itself, to any other package model like *.pkg or =
S-parameter. If go to IBIS open forum to search all the ibis model, so =
far I did not find any of them really using .pkg model with their ibis =
model. If the chip get low pin count, I think it is easy to handle *.pkg =
model because it is possible to verify accuracy for all the parasitic =
effect. But for big chip, I don't know is there any way can handle that?
  For most of the application, I guess, probably it is not necessary to =
provide .pkg model with ibis, because it may only provide one or two =
order accuracy than per-pin R/L/C format in ibis. Tool compatibility may =
be another issue.

Best Regards,

Eric Hsu
Interface Technologies
Netlogic Microsystems, Inc.
450 National Ave.
Mountain View, CA 94043
650-961-6676 x198
This e-mail contains Netlogic Microsystems, Inc. Confidential =
information

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Received on Fri Mar 12 05:54:22 2004