[SI-LIST] Re: Question on PDN simulation with Linear Technology spice
- From: istvan Novak <Istvan.Novak@xxxxxxx>
- To: "Moreira, Jose" <jose.moreira@xxxxxxxxxx>
- Date: Mon, 15 Sep 2008 09:12:21 -0400
Jose,
I am afraid there is no easy generic solution to what you want to
achieve, but there are several approximations dependent on what you want
to do:
- If you use LT SPICE because you want to simulate in the time domain a
Linear Technology switching or linear converter together with your
measured board impedance, you can create an equivalent lumped-circuit
model approximation of the measured data by using R L C components
similar to described in Chapter 9.2 of the referenced book. The example
in the book shows it for approximating measured DC-DC converter
impedance. If you have measured board impedance, you can follow the
same procedure. For the purposes of analyzing the interaction between
the converter and the board, this approximating model does not need to
go beyond a few times of the switching frequency.
- If you happen to know the components of your board PDN (if it is not a
black box for you), you can build up its component-by-component
simulation model in LT SPICE from its elements, and you can then use the
measured data to adjust the model parameters to match the measured data.
After that you can combine the converter and board models in LT SPICE.
- dependent on what else exactly you want to simulate in LT SPICE beyond
your measured data, you may be able to do it the other way around:
simulate and create a simple linear model for everything else then
combine it with the measured data simply by adding the complex (measured
and simulated) admittances.
I hope this helps.
Regards,
Istvan
Moreira, Jose wrote:
> Hi,
>
> I have a question on simulating a Power Distribution Network (PDN) with a
> spice engine, especially LT spice from Linear Technologies.
>
> I measure my PCB PDN impedance response using the 3-step technique described
> in Novak's excellent book with a VNA obtaining the Z matrix. I then transform
> this Z-matrix into a T-equivalent model for time domain simulations.
>
> I have a very detailed model of my power supply in LT spice (that is why I'm
> forced to use LT spice).
>
> My question is how do I integrate this frequency dependent PDN Z values on my
> spice simulation (especially in LT spice). One option is of course to create
> a lumped element that approximates my measured PDN response but I wonder if
> there is a way to simply plug in the measured values (like for example I can
> do with a measured s-parameter matrix in a simulator like ADS).
>
> Thanks in advance for any suggestion
>
> Jose
>
>
>
>
>
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