Dear Abhijit This kind of problem has been talked about several month ago : ). I do not agree the "star topology". In high frequency domain, if there is no plane capacitance, the power integrity is bad. Best Regards Zhangkun 2004.7.9 ----- Original Message ----- From: "Abhijit Mahajan" <amahajan@xxxxxxxxxxxx> To: <weirsp@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx> Sent: Friday, July 09, 2004 3:36 PM Subject: [SI-LIST] Re: Is Impedance Enough for Describing the PDS? > Steve/Others. > > Would it be better then to reduce the area of power planes as much as > possible(by > localizing the power planes to only cover the pins that need it) and pack > the decoupling there? > islands of same voltage can be then connected with wide traces to the > nearest bulk cap > And finally brought together at the regulator. > > This can be vaguely be described as a "star topology" for power > distribution. > > Does anyone think there is any value in this appproach? Has it been > discussed before? > > > ##I am assuming all signal routing is over a common ground plane. > > > Thanks! > > Abhijit. > > > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On > Behalf Of steve weir > Sent: Friday, July 09, 2004 6:04 AM > To: zhang_kun@xxxxxxxxxx; si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Re: Is Impedance Enough for Describing the PDS? > > > Zhangkun, the problem is that the PDS overlaps both signal integrity and > EMC compliance. If the system rules are done right, then the PDS > decoupling problem will eventually reduce to an impedance profile. But > that profile is both spatial and frequency dependent. If I shove all the > decoupling capacitors into one corner of the board I get a very different > result than if I distribute them. > > Steve. > At 08:04 AM 7/9/2004 +0800, zhangkun 29902 wrote: > >Dear all > > > >When talking about power delivery system with other engineer, there are > >a > >lot of element to describe the PDS, such as energy storage, decoupling, > >bypassing, and so on. I think all these parameter could be described by > >one element, impedance of PDS. > > > >Is my point right? Is impedance enough for describing the PDS? > > > >Best Regards > > > >Zhangkun > >2004.7.9 > > > >------------------------------------------------------------------ > >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 > > > > > ------------------------------------------------------------------ > 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 > > > > > > > ------------------------------------------------------------------ > 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 > > ------------------------------------------------------------------ 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