RE: [SI-LIST] : Parallel single-ended traces routed to achieve 35 Ohm controlledimpedance

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From: Ken Cantrell (Ken.Cantrell@srccomp.com)
Date: Tue Oct 31 2000 - 08:18:06 PST


Sounds like the cart is before the horse. I would ask why 35 ohms in the
first place. Then if that is a valid requirement, you need to design your
stack up so that you will get 35 ohms across all layers of the board. If
other signals require a Zo of 70 ohms, and these particular traces require
35 ohms, it sounds like there was not enough upfront design going on during
layout. Going back to the drawing board may be the fastest way to resolve
your problem.
-----Original Message-----
From: owner-si-list@silab.eng.sun.com
[mailto:owner-si-list@silab.eng.sun.com]On Behalf Of
Salvador_Aguinaga@3com.com
Sent: Friday, October 27, 2000 2:28 PM
To: Michael Nudelman
Cc: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : Parallel single-ended traces routed to achieve
35 Ohm controlledimpedance

I need to run the trace through the a pin field. The room between pins is
2mm
and because of the dielectric thickness constraint I can only run a single
12
mil wide line through the pin field. If I use a single 35 ohm line, the
trace
width is too large to fit through the pin field.

Thanks,
-- Sal

Michael Nudelman <mnudelman@tellium.com> on 10/27/2000 03:10:31 PM

Sent by: Michael Nudelman <mnudelman@tellium.com>

To: Salvador Aguinaga/MW/US/3Com
cc: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : Parallel single-ended traces routed to achieve 35
Ohm
      controlledimpedance

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