ron miller wrote: > Hi Fabrizio > > I take a slightly different approach to noise on the boards. > > You are correct, in my estimation, looking at the power planes > coupling noise into > the sensitive signals and being mixed with the SSO degradation. > > However, what appears to random noise is often the non-coherent > summation of several > signals around the board. PCI, ethernet, serial bus, i2c and any > other clocks would be > included in this catagory. The coupling means is the return paths, > ground or power planes being > shared by the sensitive signals. > The first method of determining if the noise might be crosstalk from > many frequency sources is to > put an oscilloscope(differential probe) on signals in the vicintity of > the sensitive signal, set the triggering to normal and adjust the > trigger level until it triggers about once per second. Adjusting > the sweep speed will help to prove it is periodic and to get the peak > level(read the trigger level). > > Identifying the source is best done using a spectrum analyzer with a > small ~ 10pf Cap to keep from > loading the circuit. Once the levels of the various noise sources is > measured, adding their power > levels together(correcting for the loss of the capacitor vs frequency > into the 50 ohm scope) the peak > value that can occur should be similar in magnitude to the peak seen > with the oscilloscope adjusted to > just barely trigger. > > SSO noise(board induced component) can be measured directly at the > power pins, but the chip > level SSO can not be directly viewed, and the package is a big part of > the reactance generating > the SSO noise. Simulation using realistic package models is the only > practical method for knowing > what Simultaneous High-Current Switching at the die, will do to the > power rails and how it may > effect the signal. > Good hunting. > > Ron Miller > > > > > Fabrizio Zanella wrote: > >> I'm trying to quantify the amount of SSO noise which is contributed by >> the pc board power delivery system (vias, decoupling, stackup), with the >> goal of separating this noise from the SSO noise which is contributed by >> the device and its package. >> Has anyone attempted to measure this effect, and if so, what would be a >> good technique? I have two boards available, one with devices populated >> and the other with some BGAs depopulated, so I have access to the vias. >> Thanks and regards, >> >> Fabrizio Zanella >> Principal Hardware Design Engineer >> Broadbus Technologies >> >> -------------------------------------------------------- >> >> >> This email message and any files transmitted with it contain >> confidential information intended only for the person(s) to whom this >> email message is addressed. If you have received this email message >> in error, please notify the sender immediately by telephone or email >> and destroy the original message without making a copy. Thank you. >> >> ------------------------------------------------------------------ >> 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.org >> >> 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 >> >> >> >> >> > -- Ronald B. Miller, Microwave/SI Engineer RAIL = NOISE + REFLECTIONS Gigahertz Data Div of MI Corp. \\ // \\ // 7180 Thornton Avenue \\// \\// Newark, CA 94560 ->JITTER<- EYE ->JITTER<- tel 510-793-4744, //\\ //\\ fax 510-742-6686 // \\ // \\ www.ghzdata.com RAIL = NOISE + REFLECTIONS ------------------------------------------------------------------ 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.org 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