Re: [SI-LIST] : measuring Differential pairs

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From: Dima Smolyansky (dima@tdasystems.com)
Date: Thu Aug 03 2000 - 08:36:42 PDT


Sean:

You need to connect your TDR scope Channel 1 and Channel 2 to your
differential pair, and put the scope into differential mode.

Read Channel 1 only to get the odd mode impedance.

Subtract Channel 2 from Channel 1 to read the differential impedance.

Since you are looking to do a measurement, it does not matter whether you
have broadside or edge to edge lines, as long as you have a differential
probe that you can connect to your lines.

If your lines change impedance or spacing between the lines, you may need to
be aware of the multiple reflections in the TDR scope that slowly decrease
the impedance readout accuracy.

-Dima
===================
Dima Smolyansky
TDA Systems, Inc.
11140 SW Barbur Blvd., Suite 100
Portland, OR 97219
(503) 246-2272
(503) 246-2282 (fax)
(503) 804-7171 (mobile)
http://www.tdasystems.com
The Interconnect Modeling Company(TM)
----- Original Message -----
From: Sean Murray <seandm@mmspec.com>
To: <si-list@silab.eng.sun.com>
Sent: Wednesday, August 02, 2000 11:15 AM
Subject: [SI-LIST] : measuring Differential pairs

> How does one go about measuring (using TDR) differential pairs on a board.
> In other words, how does one measure the ZOD of the pair, be it broadside
or
> edge-edge?
>
> 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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