Taking what I said "This gives a rough inductance number" to indicate that I was not aware of the loss may not be exactly what I was getting at. What I may have been getting at is that the bead is not a resistor. Yes there is loss. Yes there is inductance. I guess that rough may not be interpreted as having a lack of accuracy. Perhaps I should have used a more precise term. The results, as observed in a situation that was quite similar to the original post, happen to have occurred. Using a bead with some capacitance and loading the result with a clock chip that has a little bit of SSO at a frequency near the resultant resonant frequency, even if there is some loss, will cause some problems. I am sorry if I caused you some concern. I will try to implement better descriptive language in the future. dav0 --- Brent DeWitt <bdewitt@xxxxxxxxxxxxx> wrote: > David, > > I think you may have started with a bad assumption by modeling the bead as > equivalent L only to get Z. The manufacturer should have curves for the > loss tangent of the bead at various frequencies. Filter beads are designed > to have the loss component dominant in the optimum design frequency range. > > Brent DeWitt > Datex-Ohmeda > Louisville, CO > > -----Original Message----- > From: si-list-bounce@xxxxxxxxxxxxx > [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Dav0 Lieby > Sent: Thursday, December 04, 2003 11:55 AM > To: Glick, Gene (IndSys, Interlogix); SI-LIST > Subject: [SI-LIST] Re: nonlinear in power ground noise of clock driver > > > I understand that the bead is a little > lossy. It is also an inductor. In the > instance that I talked about I calculated > the inductance by using the impedance at > frequency numbers associated with the > bead. This gives a rough inductance > number. The inductance is much higher > than the package would indicate alone. > Take a look at some curves. > > dav0 > David Lieby > Siemens Medical Systems, Ultrasound Division > > > > --- "Glick, Gene (IndSys, Interlogix)" <gene.glick@xxxxxx> wrote: > > I'm no expert in beads, but I thought they exhibit a frequency dependent > > resistance (as opposed to Z, like an inductor). If you are correct about > a > > resonance between the bead and the capacitor, in theory, it would be due > to > > the package inductance of the bead, right? If that's true, wouldn't a > > resistor have the same problem? Maybe the package size you used was > > different, and the resonant frequency moved elsewhere out of the trouble > > zone. > > > > If beads do exhibit inductance, then how much so? > > > > gene > > > > -----Original Message----- > > From: si-list-bounce@xxxxxxxxxxxxx > > [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Dav0 Lieby > > Sent: Thursday, December 04, 2003 12:42 PM > > To: SI-LIST > > Subject: [SI-LIST] Re: nonlinear in power ground noise of clock driver > > > > > > I had this experience a while ago. > > It boils down to the bead and the > > capacitance. We found a resonant > > circuit. Various capacitors gave > > huge noise results, another lot of > > them was OK. The final solution > > we did was to replace the bead with > > a resistor, the clock chip did not > > eat too much current so it did not > > go out operational range. > > > > dav0 > > David Lieby > > Siemens Medical Systems, Ultrasound Division > > > > __________________________________ > > Do you Yahoo!? > > Free Pop-Up Blocker - Get it now > > http://companion.yahoo.com/ > > ------------------------------------------------------------------ > > 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 > > > > > > __________________________________ > Do you Yahoo!? > Free Pop-Up Blocker - Get it now > http://companion.yahoo.com/ > ------------------------------------------------------------------ > 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 > > __________________________________ Do you Yahoo!? Free Pop-Up Blocker - Get it now http://companion.yahoo.com/ ------------------------------------------------------------------ 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