[SI-LIST] Re: Power Distribution Modeling Techniques
- From: Bill Owsley <wdowsley@xxxxxxxxx>
- To: ryan.satrom@xxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Tue, 22 May 2007 13:28:11 -0700 (PDT)
Dr. Johnson also explains how scaling works, that the same principles at work
apply across the frequency spectrum by changing dimensions.
And in another section, or maybe it was a editorial paper in a publication,
he explains the something called spreading inductance, which is basically
inductance of a circle surrounding the injection point of a PDS. I haven't
found anything dated about the information Dr. Johnson presents, after all it
is based on principles that are about 2 centuries old now (large rounding at
work)
ryansatrom <ryan.satrom@xxxxxxxxxxx> 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My other concern with Dr Johnson's book is that it may be out of
date.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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