Hi folks, I would like to add some general consideration about this issue. More than often in SI and EMC arena we have discussion on what will be the effect of this or that design technique, and many good answer based on experience come out. Then we make the effort to generalize these experience in guideline in the effort to reuse them to achieve good SI/EMC quality. Sometime in this way we loose an important point: problem like PDS in a PCB is something that could be really complicated due to the geometric complexity of the structure and to the fact that this problem require an understanding of the electromagnetic behaviour of the PCB. While a deep understanding of the general physics, behind the problem, is essential, it should be clear that an adequate tool is required to find the optimal solution to it . IN other words, I would change the question from what is the best design tecnique to solve this particular problem; to what are the tools to be used and what is the best methodologie To me this could be applied to several question in SI/EMC Giancarlo ----- Original Message ----- From: "Abhijit Mahajan" <amahajan@xxxxxxxxxxxx> To: <weirsp@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx> Sent: Friday, July 09, 2004 9:36 AM 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