Re: [SI-LIST] : High Speed Queries

Roland F. Portman (portman@bitmicro.com)
Fri, 06 Nov 1998 10:20:57 -0800

Lum Wee Mei,

Signal Integrity and PCB layout is not easy is different for each and every
application, but it can be learned.

The first thing to do purchase a copy of

High-Speed Digital Design : A Handbook Of Black Magic
By Johnson, Howard W. / Graham, Martin
http://www1.clbooks.com/asp/bookinfo/bookinfo.asp?theisbn=0133957241

CONTENT HIGHLIGHTS:

Covers signal reflection, crosstalk, and noise problems that occur in
high-speed digital machines (about 10 megahertz).

Includes checklists that ask the questions an experienced designer would ask
about a new system.

Offers useful formulas for inductance, capacitance, resistance, rise time, and
Q.

Explains the trade-offs between signal crosstalk, mechanical fabrication of
tolerances, and trace routing density.

Presents a methodology for determining how many layers will be required to
route a printed circuit board.

======================================================================================

The second thing to do is sit down for a couple undisturbed days and read it
very carefully.
Then read it again.
======================================================================================

Thirdly log onto Howard's web page www.sigcon.com - read, read, read.
======================================================================================

Fourthly, purchase a copy of the following book and read it thoroughly as
well.

EMC and the Printed Circuit Board: Design, Theory, and Layout Made Simple by
Mark Montrose

Contents : EMC Fundamentals; EMC Inside The PCB; Components
and EMC; Image Planes; Bypassing and Decoupling;
Transmission Lines; Signal Integrity and
Crosstalk; Trace Termination; Grounding
Copyright : 1999
Format : Hardcover
Pages : 320pp
List Price US$ : $69.99
IEEE Member Price US$: $56.00
IEEE Product No. : PC5756-QAJ
ISBN : 0-7803-4703-X
http://www.ieee.org/products/ordinfo.html
======================================================================================

After all this reading, you can probably answer a lot of your own questions.
But remember, there
is not just one solution and it is not an easy subject matter. It takes
knowledge, experience and
some guesswork.

Finally, may I suggest you get a Signal Integrity (SI) tool. There are
several like Viewlogic's XTK
and Mentor's IS. The one I like is Hyperlynx. (www.hyperlynx.com) Mainly
because it is very easy to use,
secondly because you don't have to sell your first born son to get it. It may
not be as accurate
as the previous two, but I don't have to hire a guru to run it.

LineSim is a good first cut - but you have to lay out the signal topology
yourself one at a time.
It is ok for scratch pad work and pre-planning.
BoardSim lays out all the signals at once by reading in your actual board
layout from your CAD tool.
BoardSim willl let you approximate things with the generic models it provides,
but you WILL have to
learn what IBIS models are before you can really make use of BoardSim.
http://www.eia.org/eig/ibis/ibis.htm

Download the demo and take a look.

Like I said, SI and PCB layout is not easy, but with some reading and
experience you can get along
just fine.

Good Luck,

Roland

Lum Wee Mei wrote:
>
> Hi, Todd and the rest in this mailing list:
>
> I am a "new kid in town" and is task to look into the high-speed design area. I understand this is not an easy topics and I hope to get some expert guidances from all of you. I have to come out with design rules so as that designs
> require such area can refer to. Have someone draft a set of high speed design rules that can share with me?
>
> I have the following queries that that some of you might able to help me. They are:
>
> 1. How you identify high speed signal? By its rise time or by its operation?
> 2. Someone told me that all high speed signals have to be impedance controlled. Is this correct? If not, what signals should be impedance controlled.
> 3. I come across a so-called high-speed board which has many vias being punched on its fill (for both ground and power) along side the pads for inductors and capacitors. They are also found on very thick ground traces. What are
> the purposes of such vias? Did they play a role in high speed?
>
> I look forward to your reply.
> Thanks and regards.
>
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-- 
Roland F. Portman
BiT Microsystems, Inc.
48499 Milmont Drive
Fremont, CA  94538

(510) 623-2341 Ext 129 (510) 623-2342 Fax

portman@bitmicro.com http://www.bitmicro.com

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