[SI-LIST] Re: Mystery TDR Waveform
- From: "Dima Smolyansky" <Dima.Smolyansky@xxxxxxxxxxxxxx>
- To: <levinpa@xxxxxxxxxxxxx>,"SI-List Reflector" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 18 Mar 2004 15:11:31 -0800
Paul,
A shunt capacitance does not necessarily starts with a steep down slope and
gentle upward slope, so I would not be surprised if it was a shunt
capacitance. However, other things are possible, of course. The inflection
points you are referring to may be a result of a small stub in a socket (if
a socket is present in your test fixture) - for example the stub due to the
socket pin going into the board. If you provided more details about your
test fixture, or some information about the size of your dip in the TDR
waveform, I could possibly offer more intelligent guesses :-).
Thanks,
===================
Dima Smolyansky
TDA Systems, Inc.
4000 Kruse Way Place
Bldg. 2, Suite 300
Lake Oswego, OR 97035
(503) 246-2272
(503) 246-2282 (fax)
TDA's MeasureXtractor is the EDN Product of the Year Finalist!
http://www.tdasystems.com/products/measurextractor.shtml
----- Original Message -----
From: "Paul Levin" <levinpa@xxxxxxxxxxxxx>
To: "SI-List Reflector" <si-list@xxxxxxxxxxxxx>
Sent: Thursday, March 18, 2004 1:59 PM
Subject: [SI-LIST] Mystery TDR Waveform
> Dear All,
>
> I was wondering if someone could give me a hint as to what might
> be behind an unusual bit of TDR waveform I've encountered.
>
> Hopefully if you use fixed type width the following will look oK:
>
>
> xx x
> xx x
> xx x
> xx x
> xx x
> xx x
> xx x
> xx x
> xxxx
>
> The 50 ohm baseline is the starting value at the left of the
> plot and the right end of the plot soars up to open circuit,
> as expected since there is an open circuit at the far end of
> this test fixture. There is something of an inflection point
> on the way down where the slope changes; the break in my plot
> is not the result of mis-counting with space bar.
>
> If the TDR started with a steep down slope and a gentle climb
> I would not hesitate to call this a shunt capacitance, but
> this behavior baffles me.
>
> Thank you in advance for any advice!
>
> Regards,
>
> Paul
>
> --
> Paul Levin
> Senior Principal Engineer
> Xyratex Storage Systems
>
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