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

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From: Salvador_Aguinaga@3com.com
Date: Fri Oct 27 2000 - 13:28:26 PDT


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


E-r-r-r....Any particular reason for doing this exercize?

Salvador_Aguinaga@3com.com wrote:

> Has any one tried to achieve controlled impedance for a single-ended trace by
> running two traces in parallel?
>
> ==================== GND PLANE
> DIELECTRIC THICKNESS T1
> +-----+
> |/////| SINGLE TRACE 70 OHMS
> +-----+
>
> DIELECTRIC THICKNESS T2 (T2>T1)
>
> ==================== GND PLANE
>
> +-----+
> |/////| SINGLE TRACE 70 OHMS
> +-----+
>
> ==================== GND PLANE
>
> Using this trace geometry, if each trace is 70 Ohms relative to its reference
> planes, and I tie them together at the ends, will this yield 35 Ohms or
> something a little less than half Zo of each trace?
>
> Thanks,
> -- žal Aguinaga Jr.
> -- 3Com - Carrier Business Networks
> -- Mt. Prospect, IL
>
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