[SI-LIST] Re: Mysterious "glitch" in the simulation?
- From: "Beal, Weston" <Weston_Beal@xxxxxxxxxx>
- To: "Nguyen, Cuong - EDA Direct" <cuong@xxxxxxxxxxxxx>, 'steve weir' <weirsi@xxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Tue, 26 Jul 2011 23:52:47 +0000
Cuong,
The glitch is a reflection from the die. The IBIS model includes a pin model
that the simulator represents with a transmission line. Therefore, the
measurement point at the pin is between to transmission line segments. The
impedance of the buffer at the die is most certainly not the same as the
impedance of the transmission line representing the package. There are
termination techniques that can remove the glitch, but each method has an
associated cost. As others have stated, you probably don't need to worry about
this small reflection.
Weston
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Nguyen, Cuong - EDA Direct
Sent: Tuesday, July 26, 2011 4:38 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:
> Content-Type: text/plain;
> charset="us-ascii"
> Content-Transfer-Encoding: 7bit
> 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
>
>
>
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List technical documents are available at:
> http://www.si-list.net
>
> List archives are viewable at:
> //www.freelists.org/archives/si-list
>
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
--
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
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
