[SI-LIST] Re: nonlinear in power ground noise of clock driver
From: Dav0 Lieby <dav0x@xxxxxxxxx>
To: "Glick, Gene (IndSys, Interlogix)" <gene.glick@xxxxxx>,SI-LIST <si-list@xxxxxxxxxxxxx>
Date: Thu, 4 Dec 2003 10:54:44 -0800 (PST)
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
>
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