Zhiping Yang Wrote: > In the measurement method you discribed below, you actually > measured the total loop inductance ( L_cap+L_vias+L_plane), > is it right? There should are some ways to seperate the L_vias > and L_plane from the L_totlal, since L_cap is more meaningful > for some PDS tools. It is always harder to define/extract partial > inductance than loop inductance since loop indutance is always > constant. > > > Hi Zhiping: Useful insight can be gained by expressing (and analyzing) the total PCB mounted loop inductance by summation (as implied in your post): L_total = L_cap + L_vias + L_plane Some of Larry Smith's writings indicate that the inductance of mounting pad and via ( L_vias) which are geometry dependendent range from 50 pH to 3000 pH, and that L_plane ranges from 50 pH to 1000 pH (depending on PCB dielectric thickness and capacitor location). Two series resonances can emerge: f0_self = 1/(2pi*sqrt(C * L_cap)) and f0_mounted = 1/(2pi*sqrt(L_total * C )) Where, f0_self and f0_mounted represent the ( un-monuted ) self series resonant and PCB mounted series resonant frequencies of a ceramic capacitor ( of value C ) respectively. Larry has earlier explained that it is easier first measuring the resonant frequency then determining ESL. Let us solve for each inductance: L_cap = 1/ [C * (2 * pi * f0_self)^2 ] L_total = 1/ [C * (2 * pi * f0_mounted)^2 ] Since L_total is larger than L_cap, then f0_mounted should be smaller than f0_self . Best Regards, Abe Riazi ServerWorks ------------------------------------------------------------------ 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 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