[SI-LIST] Re: How can I simulate the influence of power plane noise on the signal trace ?

  • From: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>
  • To: <weirsi@xxxxxxxxxx>
  • Date: Sat, 14 May 2005 14:20:17 -0700

Hi Steve,
I'm also a bit curious about your comment, and wonder if others agree.
Do you have any papers I could refer to that clearly document this
occurring?  Maybe I'm missing something, but assuming the traces are
closer to the ground plane than the power plane (or at least no further
than), it seems like if:
1) the planes are very close together, the inter-plane capacitance would
keep the AC potential between the planes at 0, or=20
2) the planes are far apart, there wouldn't be substantial noise coupled
from the power plane to the traces.

Hmmm - I wonder what would happen if I went in the lab and, for the
stackup described, hooked up a signal generator between the power and
ground planes. What would I see on a TDR (which is referenced to
ground)?  I don't think I'd see effects from the induced noise.  Perhaps
if I injected the signal using ground as a reference and then used the
power plane as the reference plane at the receiver - bad.  The amplitude
of the signal would vary with the noise.

But I'd sure like to see where this effect is quantified (which is what
I think the original intent was).  Besides a rule-of-thumb that says
"don't ever do it!", how can we characterize it and decide when it's ok
and not?

For Zhangkun - I'd be leery of referencing high-speed signals to power.
As has been pointed out on this list before, at some point you probably
have to get back to ground reference, and that can be problematic.


Jeff Loyer


-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of zhangkun 29902
Sent: Friday, May 13, 2005 5:22 PM
To: weirsi@xxxxxxxxxx
Cc: jgxian@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: How can I simulate the influence of power plane
noise on the signal trace ?

Steve

In the realistic, there have to be some signal refered to power plane.
Moreover, I do not think it is very cirtical if the decoupling for the
power delivery system.

I have use 3D field solver to simulate this kind of situation. There is
displacement current between planes, which gives rise to problem. If the
displacement current could be lessen, I think it is no critical for the
signal to refer to any plane.

Best Regards

Zhangkun
2005.5.14

----- Original Message -----
From: steve weir <weirsi@xxxxxxxxxx>
Date: Saturday, May 14, 2005 1:43 am
Subject: [SI-LIST] Re: How can I simulate the influence of  power plane
noise on the signal trace ?

> Jia, if you assume that:
>=20
> 1. The geometry of each line is identical
> 2.  The noise does not violate the CM range of the receiver,
> 3. The CM rejection of the receiver is perfect
>=20
> Then you will not see any effects whatsoever.  Put in more=20
> realistic models=20
> for each point above and you will find:
>=20
> 1. Differential noise injection
> 2. Very bad if this happens, don't let it!
> 3. Increased jitter
>=20
> For these reasons, it is a poor idea to reference high performance=20
> links=20
> against multiple voltage rails.  It doesn't mean that you cannot=20
> do it=20
> successfully, but it does mean that you have a lot of additional=20
> homework=20
> to do, and may not be able to meet a given performance target.
>=20
> Steve.
> 11:47 AM 5/13/2005 +0800, Jia Gongxian wrote:
> >Dear all,
> >
> >I'd like to simulate the influence of  power plane noise on  the=20
> signal=20
> >traces, which are differential stripline, using the power plane=20
> as one=20
> >reference plane.That is,
> >
> >    ----------------------------------- ground plane
> >
> >           ---   ---                    differential traces
> >
> >   -----------------------------------  power plane  + noise
> >
> >  Any suggestions will be welcome.
> >
> >Thanks.
> >
> >Jia Gongxian
> >------------------------------------------------------------------
> >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 FAQ wiki page is located at:
> >                 http://si-list.org/wiki/wiki.pl?Si-List_FAQ
> >
> >List technical documents are available at:
> >                 http://www.si-list.org
> >
> >List archives are viewable at:
> >                 //www.freelists.org/archives/si-list
> >or at our remote archives:
> >                 http://groups.yahoo.com/group/si-list/messages
> >Old (prior to June 6, 2001) list archives are viewable at:
> >                 http://www.qsl.net/wb6tpu
> >
>=20
>=20
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>=20
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>=20
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>=20
> List FAQ wiki page is located at:
>                http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>=20
> List technical documents are available at:
>                http://www.si-list.org
>=20
> List archives are viewable at:    =20
>               //www.freelists.org/archives/si-list
> or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
> =20
>=20
>=20

------------------------------------------------------------------
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 FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:    =20
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
 =20

------------------------------------------------------------------
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 FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
  

Other related posts: