[SI-LIST] Re: Characteristic Impedance mesurement on PCB

The Zo of the trace is independent of the active circuits on the board.  You
should be able to measure the Zo of the board unstuffed, stuff or with power
applied and get the same results.  This assumes the Zo of the traces is not
defined by the location of other materials on the board.  For example a
shield placed over traces will affect the EM fields thus Zo.

Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
503-430-1285 FAX
tom@xxxxxxxxxxxxx
www.teraspeed.com

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827 


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of padma gundala
Sent: Wednesday, January 14, 2009 9:49 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Characteristic Impedance mesurement on PCB

Hi ,
 
I'm trying to measure the characteristic impedance of a trace(SINGLE
ENDED) on the PCB  using a TDR
This trace has a Amplifier and a DAC on it's path.
My teammate feels we need to activate it, giving the various voltages for
the amplifier.
I feel we can measure the impedance whichout activating the circuit just
like we would measure the impedance of a connector.(passive)
 
What do you'll think?
 
Thanks for any input.
 
Pam

      
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