RE: [SI-LIST] : DIFF PAIRS

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From: Larry Miller (ldmiller@nortelnetworks.com)
Date: Mon Jun 12 2000 - 13:52:42 PDT


If you got, like, 65 ohms the problem is that your dielectric thickness is
too big. If you want 8-mil traces you should be more like 0.005".

There is a handy-dandy impedance calculator available for free download at
UltraCad.com that I use all the time for "close enuf" PCB trace
calculations.

Larry Miller

> -----Original Message-----
> From: Sean Murray [SMTP:seandm@mmspec.com]
> Sent: Monday, June 12, 2000 1:35 PM
> To: 'si-list@silab.eng.sun.com'
> Subject: [SI-LIST] : DIFF PAIRS
>
> Anyone have any thought on what to use for the following numbers.
>
> Material: CE
> Impedance: ZO of the differential trace is 50Ohm and ZOD of each
> differential pair traces is 100Ohm.
>
> I built a board using 8 mill traces with a 8 gap between the pair, and
> .008 gap between plane to sig and then plane.
>
> Numbers were not what I expected, fabhouse used Polar+fudge factor to
> give me the numbers.
>
>
>
> Regards,
> Sean Murray
> General Manager
>
> M&M Specialties Inc.
> 1236 W. Southern Ave. #106
> Tempe, AZ. 85282-4518
> Phone: (480) 858-0393 x105
> Cell: (602) 684-7859
> Fax: (480) 858-1882
> Email: seandm@mmspec.com
> WWW.mmspec.com
>
>
>
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