Subject: Package Model?

From: [email-masked] (Zheng SHI)
Date: Wed, 11 Dec 96 17:38:53 PST

Hi, Ibis folks:

Thank you all for reading and answering my last question 
about Polarity and Enable sub-param. This time I met another 
problem, an I/O pin has a package model as below:

 INT------ o----/\/\/\----o----/\/\/\----o------ EXT
           |              |              |
           o----@@@@@@@---o----@@@@@@@---o
           |              |              |
           |              |              |
          ===            ===            ===
           |              |              |
           |              |              |
          GND            GND            GND

It doesn't fit the default ibis package model, so I can't 
choose the R_pkg, L_pkg and C_pkg. Still, I can't find 
ways using [Define Package Model] to deal with it.

Can anyone give me a help? Thanks a lot,

-Zheng Shi
 [email-masked]
 Los Altos, CA.

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From: [email-masked] ( Chris Reid)
Date: Thu, 12 Dec 96 09:34 PST

> ways using [Define Package Model] to deal with it.

It appears from the schematic that the purpose of the
resistors in parallel with the inductors is to approximately
model a skin-effect resistance.  One possibility here is
to model the pins as transmission lines (without the resistors)
and use a simulator that handles skin-effect directly.

I suggest you analyze the behavior of this network at
frequencies up to ~5/rise-time and see if the resistors are
actually needed to get the results you need.

Since your schematic does not include values my comments are
only a guess at the purpose.

Christopher Reid
Interconnectix

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From: [email-masked] (Zheng SHI)
Date: Thu, 12 Dec 96 10:45:33 PST

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From: "C. Kumar" <[email-masked]>
Date: Thu, 12 Dec 1996 09:33:43 -0500

The package model seems to be modelling frequecny depedndent resistor. (skin effect).
Unfortunately IBIS package model syntax is not sufficient to do that (including the new segment oriented package model syntax (yet another syntax ..sigh..)) . However the modelling can be easily accomplished if you are allowed to include spice subcircuits which I am a proponent of.

If you beleive enabling spice subcircuits is important I urge you to raise it in the IBIS meeting (which is announced ) directly.

- kumar

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