[SI-LIST] Re: Mysterious "glitch" in the simulation?
- From: Peter.Pupalaikis@xxxxxxxxxx
- To: <si-list@xxxxxxxxxxxxx>
- Date: Wed, 27 Jul 2011 11:45:38 -0400
I agree with Todd. I co-authored a DesignCon paper on this topic - but
from a measurement and probing problem perspective.
You might find something interesting in there.
http://www.lecroy.com/files/WhitePapers/DesignCon_2010_WP.pdf
Pete
P.S. I apologize for my previous Blackberry problem a few weeks ago when I
was reading Yuri's e-mail on the definition of voltage. If you recall, my
intelligent response to his comments was "R". The lesson is to not read
SI-LIST posts on family vacations at Hershey Park on your Blackberry. At
least I got to find out everyone on the SI-LIST who was on vacation by the
bounce-back messages!
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|07/27/2011 11:35 AM
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|[SI-LIST] Re: Mysterious "glitch" in the simulation?
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Cuong,
The "glitch" you're seeing at the pin is characteristic of a
series-terminated topology and is to be expected.
Try breaking the transmission line into two pieces, probing in the middle,
and see what happens.
I covered some of the characteristic behaviors of source-terminated
systems in this presentation:
http://www.eda.org/ibis/summits/jun05/westerhoff.pdf
I had a lot of fun creating that presentation, too.
Todd.
--
Todd Westerhoff
VP, Software Products
SiSoft
6 Clock Tower Place, Suite 250
Maynard, MA 01754
(978) 461-0449 x24
twesterh@xxxxxxxxxx
www.sisoft.com
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Cuong Nguyen
Sent: Tuesday, July 26, 2011 7:38 PM
To: 'steve weir'; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Mysterious "glitch" in the simulation?
Scope photo:
http://imageshack.us/photo/my-images/34/tmp1n.jpg/
Circuit topology:
http://imageshack.us/photo/my-images/197/tmp22n.jpg/
Measurements were made at the receiver end at the pin. Measurements at
the die (not shown) do not show the glitch.
Cuong
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of steve weir
Sent: Tuesday, July 26, 2011 4:13 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Mysterious "glitch" in the simulation?
The SI-LIST server strips attachments. Post your pictures to something
like imageshack and include a link.
What is the topology from the driver to the receiver? Where are you
measuring in your simulation?
A double inflection such as a glitch implies L/C or Tx line reflection.
That the series termination does not seem to affect the glitch much
implies that the oscillation occurs between the driver and the
transmission line. Excessive package inductance and/or capacitance for
the driver's edge rate and strength could do such things to you.
Steve.
On 7/26/2011 3:48 PM, Cuong Nguyen wrote:
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> charset="us-ascii"
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> Colleagues,
>
>
>
> I'm seeing a small "glitch" in a relatively simple simulation and
> would
like
> to solicit your expert observations.
>
> Instead of showing 2 circuits and 2 scope traces I'm showing one set
> only but will try to explain.
>
>
>
> 1. The original circuit does NOT have the series R1 resistor
(17-ohm
> suggested by the wizard)
>
> 2. The scope trace shows the result of the original circuit.
>
>
>
> My observations:
>
>
>
> 1. The "glitch" stays in both cases (with or without the series
> termination)
>
> 2. With termination, the upper value of the voltage output is
reduced
> and the lower value
>
> is increased a little. The general shapes are the same in both cases.
> However, because
>
> the "glitch" is shifted down (with termination) this now crosses the
> threshold area and becomes
>
> problematic.
>
>
>
> The questions are:
>
>
>
> 1. What is this glitch? Is it from the package model? (If I
choose
> die I do not see the glitch)
>
> 2. What might be some ways to resolve this? (Or, is this some
> simulation artifact?)
>
>
>
> Thanks for your inputs
>
>
>
>
>
>
>
>
>
>
>
>
>
> === === === === === ===
>
> Cuong Nguyen
>
> Field Application Engineer
>
> EDA Direct Inc
>
>
>
>
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--
Steve Weir
IPBLOX, LLC
150 N. Center St. #211
Reno, NV 89501
www.ipblox.com
(775) 299-4236 Business
(866) 675-4630 Toll-free
(707) 780-1951 Fax
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