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