I would sure like to know who would design their PLL VCO around the global power distribution and not a dedicated power rail. 50mV of noise at the right frequency can knock a VCO out of jitter spec but that among will be more than acceptable for any global power spec. Don't mix apples with oranges. -----Original Message----- From: Ed Priest [mailto:epriest@xxxxxxxxxxxxxxxxxxx] Sent: Monday, January 19, 2004 9:35 AM To: Michael E. Vrbanac Cc: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: [SI-LIST]: Distribution/Filtering/Decoupling Guide The 100Mhz clean cut off. The scary comment wasn't about your proposal but it was about taking data off of one design and applying it. You are trying to address this problem by coming up with a method of finding out how power distribution to and noise leaving uproc, FPGA, ASICs, different designs vary. I also was not questioning other people's findings but I think that different designs can have major differences. I have seen designs that break the 100Mhz cutoff (this problem can be exacerbated if you have VCO's or resonances that are very sensitive to specific frequencies) Any one who has been in the business any length of time has seen one of the "rules" they came up with extended into places that no longer apply. That was my concern here. Mark said it well "Based on that, we can intelligently evaluate our own=20 deviations from the standards". As long as this is done then we are fine.=20 The process of coming up with a universal test platform is tough but it is being done in 2nd level qual. issues and this will have a large benefit but the amount of work to get there was fairly large. They had a similar problem - all the chips could have vastly different pinouts/sizes/etc.=20 Thanks Ed=20 ------------------------------------------------------------------ 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: http://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.org List archives are viewable at: http://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