[SI-LIST] Re: Power Distribution Modeling Techniques
- From: Istvan Novak <istvan.novak@xxxxxxxxxxx>
- To: ryan.satrom@xxxxxxxxxxx
- Date: Tue, 22 May 2007 22:21:32 -0400
Ryan,
1) Regarding books on PDS modeling, in a few weeks there will be a book
available from Artech House:
Frequency-Domain Characterization of Power Distribution Networks
ISBN 978-1-59693-200-5
Istvan Novak and Jason R. Miller
Approx. 420 pages.
Available August 2007
2) At high frequencies the main difference is that unless you deal with
physically very small structures, the
components are all inductance. So it boils down to inductance. Since
inductance
is not a very strong function of frequency, basically whatever
inductance you achieve around 100MHz
(assuming that you are beyond the series resonances of parts), you will
get something similar at 5GHz as
well, or maybe slightly less. For medium and large boards the same
applies: you get the inductance
of planes; beyond the third or fifth modal resonance peak, the impedance
profile follows the impedance
of the plane inductance.
3) It depends on what (else) you may have on the board. If you have
mostly differential current-mode
SerDes signaling, it is more tolerant to noise and generates less noise
than large-swing single-ended
signaling. In such cases the PDS design is actually simpler; you
generate less noise, and the
signaling is more robust. The critical items become the 'analog' power
domains: PLL and SerDes
power connections.
4) For plane simulations 3D simulators are required only if you need to
simulate the details of local
effects. For component placement and modal resonances any of the 2.5D
tools will do a good job.
Regards,
Istvan Novak
SUN Microsystems
ryansatrom wrote:
>All-
>
>I am interested in developing a better understanding of PDS modeling,
>but I'm really struggling to find good reference material to help
>me. To date, the best explanation of PDS modeling that I've seen is
>from Dr. Johnson's Black Magic Book. His book has helped me create a
>good general overview of PDS modeling, but I'm still unable to
>actually transfer his techniques to real-world board analysis.
>
>My other concern with Dr Johnson's book is that it may be out of
>date. The example he uses (see Ch.8) uses a Trise of 5ns
>(Fknee=3D100MHz). I am looking at 10GB/s board with a Trise of ~25ps.
>
>1) Does anybody have any other recommended references for modeling
>Power Distribution?
>
>2) At higher frequencies (5GHz+ instead of 100MHz), how do you
>ensure that the PDS maintains a low impedance. Is the solution just
>additional VCC-GND loops are required in the DUT area to further
>decrease the loop inductance of bypass network?
>
>3) Are there any new strategies that are required for boards that
>are 5GHz+?
>
>I understand that at very high frequencies, the bypass is done
>through the VCC-GND planes. My assumption is that the high frequency
>signals are constrained to very close to the DUT area, therefore the
>planes-as-bypass is only valid in very small local area.
>
>4) How can i quantify the effect of planes on the bypass network?
>Must I use 3D simulation to determine location of currents on planes?
>
>5) What type of software is best for PDS simulation? What is
>recommended. I have access to HFSS, which helps with the very small
>environments. I'd like to learn to make do with what i have somehow.
>
>I'd appreciate any and all feedback. And again, maybe all of this is
>detailed in a reference book. Please let me know if you know of any
>good books on this topic as well. Thank you very much.
>
>
>
>
>
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