| | L=18.47uH
| | R=1.6K
The problem I've found is that this model has a limited
frequency range over which the model to hardware correlation
is good. The frequency dependent nature of the ferrite material
makes this simple topology model diverge quite a bit from
reality at higher frequencies. Some of the special ferrite
blends that vendors use in EMI suppressors are quite non-linear
wrt frequency.(I've seen quite a delta as low as 10MHz on a
number of ferrite bead inductors). Also, it doesn't account
for saturation of the ferrite due to DC current.
I've never been able to get a model out of a ferrite vendor
that I felt was any better.
Does anyone have any comments and/or suggestions on ways and
means of extending the model to account for frequency and
current dependency? (or perhaps have run across any good
articles or papers addressing the issue)
Sun Microsystems Inc.
> Date: Fri, 6 Mar 1998 16:14:46 -0500 (EST)
> From: "Jeff M. Gloudemans" <firstname.lastname@example.org>
> To: email@example.com
> Subject: Re: Re: [SI-LIST] : power supply filtering and bypassing
> I've had good luck modelling ferrite beads as a parallel RLC. Usually I
> charcterize and extract the model myself. This way I can optimaze it over the
> frequency range of interest. At one time I did get some RLC models from TDK
> some of their surface mount ferrites.
> I'd probably have little fear of resonance effects if paralelling ferrites
> they are quite lossy.
> Jeff Gloudemans
> Delphi Delco Electronics Systems