On Monday 19 October 2009, Dan McMahill wrote: >Larry Doolittle wrote: >>> Good RF decoupling standard practice is to use a smaller cap >>> (e.g. 20pF in parallel with some larger ones such as 1000pF >>> _and_ 0.1uF or larger as needed) to get a good broad band >>> capacitive reactance across frequency). >> >> I have yet to see a 20pF or 1000pF cap with less parasitic inductance >> than a decent (e.g., X5R) 0402 cap up in the uF range. Say, in >> particular, >> TaiyoYuden JMK105BJ225MV-F 2.2uF 0402 6.3V X5R 0.1560 in 100's >> If you're going to occupy board area with a cap and its connection >> to the power nets, can anyone explain why I should choose anything >> other than the largest value available in that size and voltage? > >my recent experiences are more in line with Larry's. Most C for a given >package and voltage seems to be the best meaning that above resonance it >is no worse than smaller capacitance value devices and below resonance >it is better. And yes, this seems to fly in the face of what has been >recommended in the past. I've not done any careful measurements of >older technology bypass caps but I wonder if this is one of those >"rules" which became obsolete 15-20 years ago and no one noticed... > >-Dan
It may have, having been replaced with surface mounted, there leadless packages. Unforch, the traces leading to the pads then become the leads, so I have doubts one is completely home free with that approach. > >_______________________________________________ >geda-user mailing list >geda-user@moria.seul.org >http://www.seul.org/cgi-bin/mailman/listinfo/geda-user > -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) The NRA is offering FREE Associate memberships to anyone who wants them. <https://www.nrahq.org/nrabonus/accept-membership.asp> <doogie> netgod: 8:42pm is not late. <netgod> doogie: its 2:42am in Joeyland -- #Debian _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user