[SI-LIST] Re: GND Separation for Analog & Digital circuits
- From: Chris Cheng <Chris.Cheng@xxxxxxxxxxxx>
- To: "'jrbarnes@xxxxxxxxx'" <jrbarnes@xxxxxxxxx>,Chris Cheng <Chris.Cheng@xxxxxxxxxxxx>, si-list@xxxxxxxxxxxxx
- Date: Wed, 25 Feb 2004 14:41:53 -0800
It all sounds great to promote your book and your service. But my question
remains, why does one need to create mesh power planes on PCB and what is
the technically reason behind it. Have you yourself done any work to justify
the methodology ? I read your response and 99% of it seems to be a book and
service promotion coupled with a pile of MCM reference paper that has
nothing to do with PCB design. In am interest in your personal technical
answer. Did I miss anything ?
-----Original Message-----
From: John Barnes [mailto:jrbarnes@xxxxxxxxx]
Sent: Wednesday, February 25, 2004 2:10 PM
To: Chris Cheng; si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: GND Separation for Analog & Digital circuits
> What do all these MCM papers promoting mesh power distribution to do
> with PCB power distribution design ? There are many reasons why MCM
> or ultra fine pitch substrates use meshed power/gnd planes. They vary
> from degassing requirements on organic substrate to via and
> interconnect constrain like IBM TCM. However, they are fundamentally
> different to regular PCBs. I have design many MCM and fine pitch
> packages and I have never seen a mesh design out perform electrically
> over a conventional solid reference planes PCB. The practice came out
> from process requirement more than performance enhancement. I don't
> see why it should be promoted in places where it is not necessary.
Chris,
Peter's initial posting said that he was looking for additional
information on Power Mesh Architecture. I tried to oblige. The 9
papers that I cited represent less than 1.3% of the reference documents
that I have in my file on designing power distribution for electronic
products and equipment.
To me, power distribution on a chip, package, printed circuit board,
subsystem, system, and installation are all part of a continuum.
Strategies, techniques, ideas, and analyses that are commonly used on
printed circuit boards may also work at the module-packaging level, or
at the subassembly/system level, with a little tweaking to meet the
particular situation--and vice versa. I consider the utility of ideas
based on their own merits, not on what they are called, how they are
currently used, who came up with them, or where I happen to find them.
I am continuously searching for viewpoints, strategies, techniques, and
ideas that can help me on current and future projects--and since I
consider my job function as an Engineer is to "make things work"--that
covers a lot of territory... On the average, 95% of the 300 books and
900 magazines/journals that I read cover-to-cover per year are technical
in nature. I currently have 16 bookcases of electronic books, 8
bookcases of databooks, and 6 bookcases of electronic magazines/journals
in my personal collection, along with 20+ piles of electronics magazines
that I've read, but haven't gotten around to sorting and putting away
just yet.
Chapter 28 "Bypassing, Decoupling, and Power Distribution" in my new
book(s), Robust Electronic Design Reference Book, Volume 1 and 2 (to be
available in late March http://www.wkap.nl/prod/b/1-4020-7739-4 ) is
42 pages long and is based on 480 reference documents that I had
collected on the subject as of mid-November last year.
Already this year, two products that clients brought to dBi for FCC and
CE Mark EMC/EMI/ESD testing and approvals had power distribution
problems. Both problems took us longer to find and fix than I thought
they should. With my latest book(s) out of the way (see above), which
chewed up some 4,200 hours of my time last year, I'm digging even deeper
into the subject. So far I have:
* Searched for the titles of all the papers written by 480
authors, who were listed as the author/co-author of at least one
book/report/paper/article/application note on the subject.
* Gone though every issue I can find of 8 electronic engineering
magazines/journals.
* Gone through the every proceeding I can find for 5 electronic
engineering symposiums/conferences.
* Searched 34 web sites for pertinent application notes.
I still need to read through about 12 inches of 2003/early 2004 EDN and
Electronic Design magazines, and search another 44 web sites that have
had at least one web page or .pdf file on bypassing, decoupling, and
power distribution. Only then will I consider my search complete, and
my bibliography ( http://www.dbicorporation.com/pwr-bib.htm ) brought
up to date again--at least for awhile. Of the 220+ additional
references that I have found and bookmarked/photocopied/printed out
since late January, so far I've only found three ideas that aren't in
Chapter 28 of my book. And none of them would help me crack my clients'
problems any quicker. But I keep hoping...
John Barnes KS4GL, PE, NCE, ESDC Eng, SM IEEE
dBi Corporation
http://www.dbicorporation.com/
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