[SI-LIST] Re: SwItChING FREQUENCY IN SPECCTRA QUEST
- From: Bill Wurst <billw@xxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 26 Apr 2005 09:10:19 -0400
Hi Race,
For starters, I would do a frequency sweep of just the bead model in
SPICE to plot Zbead vs. frequency. If the plot comes reasonably close
to that published in the manufacturer's datasheet (i.e., same shape and
roughly the same corner frequency (or frequencies if there is a higher
frequency corner in addtion to the first corner), then I would conclude
that something else is causing the resultant waveforms to exhibit
non-monotonic behavior. Without knowing much else about the circuit,
it's difficult to say what, but it has often been said that engineering
is like peeling an onion: after you remove the first layer, that
exposes another layer, which in turn exposes another layer, and so on.
Best wishes as you troubleshoot your circuit.
-Bill
==================
race wrote:
>Thanks Bill.
>
> The simulation failed to deliver the results I
>had expected.
>
>I was trying to do some post route simulations to verify signal integrity
>and
>timing for busses particularly. The simulation either failed to deliver the
>expected results or the results
>were all NAs. Usually the resulted signal is nonmonotonic.
>
>regards
>
>
>
>----- Original Message -----
>From: "Bill Wurst" <billw@xxxxxxxxxxx>
>To: <si-list@xxxxxxxxxxxxx>
>Sent: Friday, April 22, 2005 8:45 PM
>Subject: [SI-LIST] Re: SwItChING FREQUENCY IN SPECCTRA QUEST
>
>
>
>
>>Race,
>>
>>Your best bet is to get the model from the manufacturer. However, if
>>the manufacturer's datasheet contains a plot of Z vs. frequency, then
>>you have enough information to develop your own model. Ferrite beads
>>generally follow the impedance of a parallel LRC circuit. If a
>>single-stage parallel LRC gets you reasonably close to the published Z
>>vs. f curve, then you're done. If not, try adding additional parallel
>>LRC stages in series with the original, adjusting the impedance of each
>>to give the desired result. Admittedly, this is a somewhat heuristic
>>approach, but I have used it before with success. Regarding the
>>switching frequency, you will want to make sure that your model
>>accurately represents the impedance of the bead from the fundamental of
>>the switching frequency to the highest harmonic of interest, which will
>>depend upon your application.
>>
>>When you say that the simulation failed, was it that SPICE failed to
>>execute, or was it that the simulation failed to deliver the results you
>>had expected?
>>
>> -Bill
>>
>>
>> /************************************
>> / billw@xxxxxxxxxxx /
>> / /
>> / Advanced Electronic Concepts, LLC /
>> / www.aec-lab.com /
>> ************************************
>>
>>==============================
>>race wrote:
>>
>>
>>
>>>>hello to all,
>>>>
>>>>GOod afternoon!
>>>>
>>>>I am an SI trainee. I was tasked to do some simulations on one of our
>>>>boards.
>>>>
>>>>Im looking for a ferrite bead espice model from murata;
>>>>PART NAME: BGLM18AG121SN1D. I have tried sending inquiries to murata but
>>>>
>>>>
>>>>
>>>>
>>>got
>>>
>>>
>>>
>>>
>>>>no reply regarding on the espice model.
>>>>I need the model for my bus simulations.
>>>>I have tried replacing the bead with a 100 ohm resistor at 100 MHz but
>>>>
>>>>
>the
>
>
>>>>simulation failed. And
>>>>by the way, how will the switching frequency affect my simulations?
>>>>
>>>>Could someone help me on this.
>>>>
>>>>ANy help is really appreciated.
>>>>regards,
>>>>race
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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