[SI-LIST] Spice modeling of ferrite beads/inductors
- From: Raymond Anderson <Raymond.Anderson@xxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 05 Dec 2003 09:20:04 -0800
The following URL points to a document that outlines how a decent spice model
for a ferrite component may be created. Also shown is the response of
'not-well-behaved' filter and sample responses of filters that have been
'tamed'. The slides shown in the document have been extracted from a training
presentation I did a while back.
http://www.si-list.org/files/tech_files/power_filt.pdf
The spice model shown utilizes the G element. The original method was
published by Michael Wyatt in the Oct. 15, 1992 issue of Electronic Design
magazine and later reprinted in the Microsim Application Notes Handbook
(Version 6, 1994).
The resulting model is created from measured/published Impedance and phase
angle information. One page in the document compares the raw data from the
vendors data sheet to the response of the synthesized spice model. The
correlation is excellent and the two curves are very nearly indistinguishable
from each other.
Note that while this method depends on Z and phase angle info, if you have
measured or published s-parameter data available there are several programs
in existance that can produce nice 'black-box' models from the s-parameter
data. It really isn't practical to massage the s-parameter numbers into a
spice model by hand, but you can simply synthesize a model from the Z data.
Note also that the S element in Hspice (and at least a couple other spice
variants) can directly accept s-parameter data.
All lumped element approximation models of ferrite components that I've seen
fail to accurately reflect the non-linear impedance versus frequency
characteristics of most ferrite components over more than a very narrow
frequency range. It seems that models based on measured data, be it
Z or S are the most accurate means of modeling ferrite components as opposed
to lumped element approximations.
The si-list.org web site still needs a bunch of work done on the menu
structure etc., but the above URL leads directly to the relevant document.
-Ray Anderson
Staff SI Engineer
Sun Microsystems Inc.
Dav0 Lieby wrote:
>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
>
>
>
>
>
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