How do you figure out propagation delay through planes? Is it sqrt(L/C) so L is about 32pH/mil of separation (sheet inductance) but what is C (which is area dependent - no concept of "sheet capacitance")? Thank you Aleks On Thu, Aug 27, 2009 at 5:25 AM, Istvan Novak <istvan.novak@xxxxxxx> wrote: > Hi San, > > If you have the good luck to have rectangular plane shapes, you can > simply calculate the > modal resonance peak frequencies from the propagation delay along each > of the two sides > of the rectangle. 1/(2*tpd) gives you the lowest resonance peak, and > you will get all of > the harmonics, so it becomes a double infinite series. On typical PCB > dimensions today, > the first five or ten resonance peaks matter in self impedance; the > higher-order modes > will tend to blend together into an inductive slope. > > For more complex shapes the modal resonance frequencies need to be > calculated by > an appropriate software. You can go from simple and low-cost tools like > EZPlane > (http://www.ems-plus.com/ezpowerplane.html) to more sophisticated tools > like > Sphinx (http://www.e-systemdesign.com/products.aspx) to high-end tools > such > as Ansoft SiWave or HFSS. For HFSS and correlation on power planes, you > can > check out the Unofficial HFSS User forum (http://www.hfss-forum.com/). > > To make sure that resonances do not create a problem, best and cheapest > defense > is to make sure you dont excite them. You can do this by creating a > stackup to > minimize signal-return currents going through unrelated power-ground > cavities. > To reduce the resonances themselves, you can either sprinkle the planes > with many > capacitors, match the planes or use thin laminates, or a combination of > these. If > you sprinkle the planes in the old-fashioned brute-force manner, you > could use the > same capacitance value, say 0.1uF or 1uF. Key is minimizing the inductance > in the capacitor connections because with the cumulative inductance of > all capacitors > on the plane you want to stay below a couple of percents of the plane's > inductance. > You can read more on these design options at > http://www.electrical-integrity.com/, > go to Paper download. In the Tool download section you can also find > simple > illustration tools for plane resonances. > > For measurement options, you can look at the paper "Frequency Domain Power > Distribution Measurements - An Overview" from DesignCon 2003 East, Boston, > MA, June 23-25, 2003. You will find it at the site above. For more > details and > tips, you can look at the book Frequency-Domain Characterization of Power > Distribution Networks, Artech House, 2007. > > Regards, > > Istvan Novak > SUN Microsystems > > > > Sandhya I. M. wrote: > > Hi SI experts, > > > > If any one can help me in doing PCB Power Plane resonance analysis by > > sharing documents or by explaining how it occurs. > > > > What are the causes of PCB Power Plane resonance analysis > > How can we measure resonant frequency > > How decoupling caps helps in suppressing resoinance in planes. > > What are the factors we should consider while doing resonance analysis. > > > > Thank you > > > > Regards > > san > > > > > > ------------------------------------------------------------------ > 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 technical documents are available at: > http://www.si-list.net > > 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 technical documents are available at: http://www.si-list.net 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