[SI-LIST] Re: Looking for a PCI connector coupled spice model
- From: Michael Khusid <mkhusid@xxxxxxxxxxxxxxxxxx>
- To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 25 Feb 2002 12:58:27 -0500
Michael,
While it is theoretically possible to build a 100ps edge SPICE model for a
PCI connector, it is hardly practical. PCI connector is not a high speed
connector, and its ground scheme was optimized for weak slow drivers
consistent with PCI spec. If you try to analyze that connector at high
speeds, you will find many impedance discontinuities and much crosstalk
between many lines in the connector. In terms of a model, that will require
very large number of mutual inductance terms which are not quite trivial to
compute using both 2.5D or 3D simulations. Once you add all elements, the
model would be very large and very slow to simulate.
Transmission style W-element representation is also hardly practical for the
PCI connector since it fails to achieve constant impedance at any point of
the connector. W-element does assume at least some reasonable length of
more-or-less constant impedance (or LC matrix if you wish).
A complete measured model of a connector is also questonable. Using off the
shelf software, you can measure good reflection and transmission profile and
have a decent model for those two characteristics. However, crosstalk will
likely be a larger obstacle when running 100ps edges through a PCI
connector, and you will find it on many quiet lines while driving just one
active line. Achieving set of consistent measurements on all victim lines
and building a complete model will be simply difficult.
My conclusion: You may not be able to find a 100ps PCI connector model, and
even if you find one, it will be very cumbersome -- otherwise, be
suspicious.
Mike
> -----Original Message-----
> From: Michael_Greim@xxxxxxxx [mailto:Michael_Greim@xxxxxxxx]
> Sent: Thursday, February 21, 2002 5:16 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Looking for a PCI connector coupled spice model
> .......
>
>
>
> that can support 100 pS edges. The one I have
> only goes down to 350 pS. Thanks for the help.
>
> MG
>
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