RE: [SI-LIST] : si-list test

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From: Franck Thierry (franckt@eicon.com)
Date: Wed Dec 01 1999 - 14:30:04 PST


Thanks for your answer. I think I missed the point. I have played with
Hyperlink software, IBIS model and layer stackup. You create a line model
with your parameters (drivers, receivers..), you simulate with LineSim, and
you've got the results (rise/fall time behaviour). When you specifie, for
example, a 50 ohms impedance, does-it mean you don't need any termination
(serie or parallel) on that line ?

-----Original Message-----
From: Mike Mayer [mailto:Mike.Mayer@cp.artesyn.com]
Sent: Wednesday, December 01, 1999 4:52 PM
To: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : si-list test

>>>>> "Franck" == Franck Thierry <franckt@eicon.com> writes:

> Gentlemen, I have a basic question regarding SI. We're beginning
> to control the impedance on our boards (due to the increase of
> the clock frequency), but I have the following question: How do
> you define the impedance ? It's not clear for me today where
> this value is coming from. PCB designer said the IC vendors
> shoud give me this information, IC vendors say to use a SI
> software and to work with PCB designer, but I have to say I'm
> lost in this. Maybe one of you could help me on that ?

The impedance of a trace on your board is a function of the physical
geometries of the trace and the properties of the board
materials. Primarily it is the width and height above a plane for
microstrips and the width and plane separation for striplines. There
are application notes around that talk about it. For instance:

http://www.fairchildsemi.com/an/AN/AN-661.pdf

If you are using TTL or CMOS devices with rise times on the order of
1nS or less (most modern parts) then you need all of the things people
have told you -- the IC vendors give you models of their I/O buffers,
and the SI software lets you simulate with the models. I would brush
up on high speed design by looking into ssome of the more popular
books on the subject. For instance:

http://www.sigcon.com/books.htm

If you can find the archives to this list there have been many threads
on books.

-- 
============================================================================
=
Mike Mayer                               Artesyn Communication Products, Inc
Senior Hardware Design Engineer          Madison, WI
Mike.Mayer@cp.artesyn.com                http://www.artesyn.com/cp
============================================================================
=

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