Re: [SI-LIST] : Pi Termination

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From: Scott McMorrow (scott@vasthorizons.com)
Date: Thu May 17 2001 - 13:58:59 PDT


Chuck gets the prize for the correct answer.

The center tap pin on many differential receivers is provided
to facilitate Tee termination of the common mode signal, usually
with a resistor and a capacitor to ground.

+ ----Rodd---
                    |-------R(even-odd)----Cap---gnd
 - ----Rodd---

50 ohm resistors for odd mode termination are often provided in
input receiver cells. Externally, the center tap pin can be connected
to a resistor whos value is the difference between the even and the
odd mode line impedance. The cap is used to eliminate DC
offset.

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com

Chuck Hill wrote:

> Perhaps I've missed the point here but, > > a Pi termination is a differential termination circuit consisting of two > resistors to ground, and a single resistor line to line. A Tee termination > circuit consists of two resistors connected in series from line to line > with an additional resistor to ground connected where the first two > resistors meet. These are both termination circuits to provide a match for > both the differential and common modes. > > Chuck Hill, consultant > > At 10:04 AM 5/17/01 -0700, SOMERVILL,KEVIN (HP-Roseville,ex1) wrote: > >Hello SI-Folks, > >Where can I find information about pi termination? I have only heard the > >term a few times and would like to understand more about how it works, when, > >and why to use it. > > > >Thank you for your time, > > > >Kevin Somervill > > > >**** To unsubscribe from si-list or si-list-digest: send e-mail to > >majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > >si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > >si-list archives are accessible at http://www.qsl.net/wb6tpu > >**** > > **** To unsubscribe from si-list or si-list-digest: send e-mail to > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > si-list archives are accessible at http://www.qsl.net/wb6tpu > ****

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