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