Thank you too all who responded. I believe you all have actually helped me here. I was getting caught up in the semantics a bit myself. I am thinking primarily in the power distribution area and the goal is to decouple the power planes and ground at high frequencies and when you add capacitors between a power plane and a ground plane you achieve this goal. Since a capacitor is actually an L-C circuit in the real world, placing many distributed capacitors over a PDS(Power Distributioin system) you are reducing L which in turn improves the high frequency decoupling between the planes.
Now I have read some papers on buried capacitance and they state you can remove bypass capacitors on the power distribution system and it seems that they are using the terms "decoupling" and "bypass" interchangeably. Would you agree with that assessment? Thank you Paul Denomme From: [email protected] [mailto:[email protected]] On Behalf Of Brian O'Connell Sent: Wednesday, April 16, 2008 2:30 PM To: [email protected] Subject: RE: Bypass and decoupling capacitor definitions. Good point. So I wasted a senior design engineer's time with this one, and his verbage seems similar, but he also said that the two the two terms, while similar, should not be considered interchangeable because bypass indicates a series event and de-couple indicates a parallel event. luck, Brian > -----Original Message----- > From: John Woodgate [mailto:[email protected]] > Sent: Wednesday, April 16, 2008 10:19 AM > To: Brian O'Connell > Cc: [email protected] > Subject: Re: Bypass and decoupling capacitor definitions. > > In message <[email protected]>, > dated Wed, > 16 Apr 2008, Brian O'Connell <[email protected]> writes: > >> welllll, I borrowed the Pressman book from one of the >> design engineers, >> and it seems to indicate that a decoupling action is, in >> fact, a hi-Z >> action. > > There is always the possibility that someone in the distant > past used > the term 'decoupling' incorrectly, and the error has persisted. > > Elementary thinking is 'voltage-mode' and so if you wanted > to 'decouple' > (reduce coupling) you would include a high series impedance (but the > term 'decouple' isn't, as far as I know, commonly used in > that context). > Shunt capacitors live in the 'current-mode' world, where you reduce > coupling by adding low impedance to earth/ground. > -- > OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk > Murphy's Law has now been officially re-named The Certainty Principle > John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc The information contained in this communication and its attachment(s) is intended only for the use of the individual to whom it is addressed and may contain information that is privileged, confidential, or exempt from disclosure. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution, or copying of this communication is strictly prohibited. If you have received this communication in error, please notify [email protected] and delete the communication without retaining any copies. Thank you. Translations of this available: Traduction disponible chez: Traducciones disponibles en: Vertalingen beschikbaar bij: http://www.viasystems.com/dynamic_page.asp?page_symbol=email_footer ____________________________________________________________________ - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
