[SI-LIST] Re: VRM Modeling of commercial DC-DC convetors
- From: "Howard Johnson" <howie03@xxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>, <sij99@xxxxxxxxx>
- Date: Fri, 12 Jul 2013 09:59:21 -0700
Dear Jack,
How about an article titled, "Voltage Regulator Model", would that help you?
http://www.sigcon.com/Pubs/edn/VoltageRegModel.htm
The article looks at the response of a common, simple, dominant-pole
regulator. The example used in the article is the Texas Instruments
PTH08T220W switching-regulator module. The article shows the observed
response of this regulator and explains how features of the measured
response waveform relate to the component values in a circuit model. The
general method in the article may help you see how to solve your problem.
I do not know whether the particular circuit model used in the article
matches the circuit model used in your simulator tool, but it sounds pretty
close. The model in the article assumes two L's and two R's, much like
yours.
About your other question, whether using typical component values will be
"close enough" for your purpose depends on the accuracy you need in your
simulation results, and whether there exist any resonances in your power
system that might produce sensitive, finicky behavior. For me, personally,
in a typical computer power system, if I can vary the typical power-system
model values plus and minus twenty percent and the power system simulation
still shows acceptable behavior (nicely damped, like in the article), then I
assume all is well and move on to the next problem. Others may differ on the
exact level of variation that they feel is "acceptable" -- that's a subject
of great debate.
...if you look here (http://www.sigcon.com/Pubs/pubsKeyword.htm) under the
keyword "power system" you will find a number of related articles about VRM
stability and power system testing that you may find interesting.
Hope that helps,
Howie Johnson
P.O. Box 1309, Twisp, WA 98856
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Jack Si
Sent: Friday, July 12, 2013 7:15 AM
To: istvan.novak@xxxxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: VRM Modeling of commercial DC-DC convetors
Dear Istvan,
I am using Dc/DC uModule LTM4616 and LDO LT1763 in my design. When i set
the PDN analysis in Allegro, it requires slew inductance(Lskew), Flat
Resistance(Rflat), Output inductance (Lout), Output Resistance(Ro). I was
not able to get the info directly from the data sheet. I referred "Power
Distribution System Design Methodology and Capacitor Selection for Modern
CMOS Technology", but it gives typical values.
My questions are,
How can i derive these values?
Whether the typical values will acceptable result?
Thanks and Regards,
Jack.
________________________________
From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
To: sij99@xxxxxxxxx
Cc: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
Sent: Friday, July 12, 2013 6:50 PM
Subject: [SI-LIST] Re: VRM Modeling of commercial DC-DC convetors
Jack,
The question is too broad, because what model you need also depends on what
simulator you use. First check with the vendor to see what models they may
have. If they have none, you can get a sample, measure, and create a
behavioral model yourself.
Best regards,
Istvan Novak
Oracle
On 7/12/2013 3:01 AM, Jack Si wrote:
> Hi Experts,
> As the part of the PDN Analysis, i need VRM model for the commercial Buck
DC-DC power module. Please suggest the accurate way to model it and use.
>
>
> Thanks,
>
> Jack
>
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