Re: [SI-LIST] : Package Parasitics Modelling

Larry Smith (ldsmith@lisboa.eng.sun.com)
Mon, 29 Mar 1999 08:15:11 -0800 (PST)

Daniel - I agree. R-L-C models worked well for packages that had
no ground or power planes because the parasitics really were similar
to lumped parameters. But in modern packages with power and ground
planes, the package parasitics are definitely distributed like
transmission lines. If the package parasitics are important enough
to be considered in a design problem, then a lumped (single) R-L-C model
does not have enough detail to give you the answer you are looking for.

regards,
Larry Smith
Sun Microsystems

> From: Daniel.Adar@ecitele.com
> X-Lotus-FromDomain: ECI TELECOM
> To: si-list@silab.eng.sun.com
> Date: Mon, 29 Mar 1999 15:26:35 +0300
> Subject: [SI-LIST] : Package Parasitics Modelling
> Mime-Version: 1.0
> Content-Disposition: inline
>
> I made some spice simulations of package parasitics effect.
> I compared the RLC model of IBIS with an ideal Transmission line (with
> zo=sqrt(L/C) and Td=sqrt(L*C).
> In both cases I drove the package model (RLC or T line) by a pulse with various
> rise time, Tr.
> I'd like to share with you the results and conclusions:
> 1. For very small parasitics (whereTd<<Tr) the RLC gave similar results to those
> of the T line, but there was no need in any model since the effect was
> negligible.
> 2. For larger parasitics there is a significant difference between the two
> models.
>
> My conclusion is that referring the package parasitics simply as R,L and C is
> incorrect.
> It should always be modelled as a T line or skipped for small values!
>
> Does anyone like to comment on that?
>
>
>
>
> Daniel Adar
> e-mail: Daniel.Adar@ecitele.com
>
>
>
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