IBIS Package Model

Mike,

Can you elaborate a little more? It sounds like you're trying to model the
ground plane in a package as a non-ideal return path. Usually we make the
assumption in transmission line analysis that the return terminals are
connected to ideal ground, but this doesn't work when you're modeling power
rail collapse on an IC due to package inductance. It sounds like you want
a package model with two ports for each signal conductor and more than two
ports for the ground conductor. Is this the case? If so, you're talking
about a 3-D package model since a package model based on a 2-D cross
section would only have two ports for a non-ideal ground.

The quick answer is that IBIS can do coupled lumped package models or
uncoupled distributed package models, but not coupled distributed package
models. In my experience, I've used multiple lumped segments to describe a
package; these were based on multiple unique 2-D cross sections with
non-ideal grounds. However, I've never seen anyone derive a coupled
distributed package model from a 3-D field analysis.

Greg Edlund
Advisory Engineer, Critical Net Analysis
IBM
3650 Hwy. 52 N, Dept. HDC
Rochester, MN 55901
gedlund@us.ibm.com

---------------------- Forwarded by Gregory R Edlund/Rochester/IBM on
03/17/99 05:21 PM ---------------------------

"Mike Lamson" <m-lamson@ti.com> on 03/17/99 07:46:27 AM

Please respond to m-lamson@ti.com

To: ibis-users@vhdl.org
cc: (bcc: Gregory R Edlund/Rochester/IBM)
Subject: IBIS Package Model

Does anyone know how to represent RLC in IBIS for a ground plane with
multiport nodes? The issues is the capacitance. The inductance and
resistance can be described between any two ports of the plane but how to
represent the capacitance in IBIS is a mystery. If the total plane
capacitance is used, it gets repeated for each port which over estimates it
in the model.

Thanks,

Mike Lamson
m-lamson@ti.com
Received on Wed Mar 17 15:47:15 1999