[SI-LIST] Re: IEEE1394/Ethernet Routing Guidelines

Just FYI, there are many free 2D field solvers around, such as=0D=0A
MEFiSTo-2D Classic, IFS Pro trail version, Sonnet Lite, and SIMIAN, and=0D=
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many free 3D solvers around, such as MEFiSTo-3D Nova, FastModel, FEKO=0D=0A
LITE, and Arpeggio.  Ansoft and APLAC have student versions of their=0D=0A
basic field solvers if you qualify.  Not all model copper thickness or=0D=
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solder mask.  IFS Pro is very easy to use.=0D=0A
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Dennis=0D=0A
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-----Original Message-----=0D=0A
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]=0D=
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On Behalf Of Eric Bogatin=0D=0A
Sent: Thursday, May 31, 2007 9:51 AM=0D=0A
To: wdowsley@xxxxxxxxx=0D=0A
Cc: si-list@xxxxxxxxxxxxx=0D=0A
Subject: [SI-LIST] Re: IEEE1394/Ethernet Routing Guidelines=0D=0A
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Bill-=0D=0A
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You are asking the SI list to give you some specific design rules to=0D=0A
follow to help you meet your design spec. I think the advice you are=0D=0A
getting is basically that the precise design rule of what line width,=0D=0A
what spacing, what dielectric thickness, what copper thickness to use,=0D=
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to achieve a particular target single ended or differential impedance,=0D=
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depends on your application and the tradeoffs you want between total=0D=0A
board thickness, manufacturing design rules, interconnect density,=0D=0A
routing constraints, design margin and cost. =0D=0A
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When you ask a general question, the information you get from this email=0D=
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group is about the process to use to find your answer, not the specific=0D=
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answers. =0D=0A
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What you are hearing from this group is that you first need to=0D=0A
understand the principles behind the question you are asking, so you=0D=0A
know if it's even the right question, and what to do with the answer=0D=0A
when you get it. =0D=0A
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Next, you need the right tools to translate general design guidelines=0D=0A
into specific design rules. =0D=0A
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If you want a narrow design margin for a target impedance, and not over=0D=
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design your products, you need an accurate analysis tool, like a 2D=0D=0A
field solver.=0D=0A
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If all you need is 10-20% accuracy, feel free to use the tables and=0D=0A
charts you see in various books. =0D=0A
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You can use a free online calculator that is accurate to between 3-10%,=0D=
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or rent a 2D field solver, for about $20 an hour from the Polar=0D=0A
Instruments web site that is accurate to 1%.=0D=0A
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When you see folks on this list saying, "do your homework", I think we=0D=
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are referring to understand the essential principles- check some of the=0D=
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books or classes or freely available feature articles already posted on=0D=
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various web sites, learn to use the tools already available to you, and=0D=
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learn to apply the principles and tools to your applications. =0D=0A
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If you don't want to do your homework so you can solve your own=0D=0A
problems, which is perfectly ok, there are a number of SI-list regulars=0D=
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who would be delighted to consult for you. =0D=0A
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--eric=0D=0A
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*******************************************************=0D=0A
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Eric Bogatin=0D=0A
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Signal Integrity Evangelist=0D=0A
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Bogatin Enterprises=0D=0A
=0D=0A
Setting the Standard for Signal Integrity Training=0D=0A
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26235 W 110th Terr=0D=0A
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Olathe, KS  66061=0D=0A
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e: eric@xxxxxxxxxxxxxxx=0D=0A
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v: 913-393-1305=0D=0A
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cell: 913-424-4333=0D=0A
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f: 913-393-0929=0D=0A
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www.BeTheSignal.com=0D=0A
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-----Original Message-----=0D=0A
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]=0D=
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On Behalf Of Bill Owsley=0D=0A
Sent: Wednesday, May 30, 2007 10:14 PM=0D=0A
To: Sam.Charles@xxxxxxxx; jeff.loyer@xxxxxxxxx=0D=0A
Cc: si-list@xxxxxxxxxxxxx; si-list-bounce@xxxxxxxxxxxxx;=0D=0A
weirsi@xxxxxxxxxx=0D=0A
Subject: [SI-LIST] Re: IEEE1394/Ethernet Routing Guidelines=0D=0A
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I went below to check what Mr.Voorhies asked for;=0D=0A
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  "...have had a very difficult time finding exact numbers for trace=0D=0A
spacing/individual trace impedence and so on."=0D=0A
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  And now I don't find in any of the suggestions (or in Mr.Voorhies=0D=0A
note) anything about copper weight, dielectric constant at what=0D=0A
frequency, trace width, distance above or between reference planes,=0D=0A
length matching, number of vias across how many layers, crosstalk=0D=0A
coupling factor and it's effect on even/odd mode impedance, pre-emphasis=0D=
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to compensate for longer lengths at higher frequencies, various "cute=0D=0A
tricks" to emulate differential signals (one I really like, nearly=0D=0A
eliminates most of the above), differential drivers or complementary=0D=0A
drivers or current steering drivers, differential to common mode=0D=0A
conversion factor, terminations, decoupling, and so on.  All the=0D=0A
books/sources referenced have all the conflicting information that Mr.=0D=
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Voorhies has already discovered.  =0D=0A
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For us, immersed in the culture (or lack of it on my part) the=0D=0A
references are like preaching to the choir, we nod our collective heads=0D=
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in agreement that those are indeed good sources and Mr. Voorhies says to=0D=
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himself, Hey I can catch lightning in a jar, but I still don't WTF they=0D=
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just said, thus the reason for his request.  Everyday we work with digit=0D=
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heads, okay, digital guys, who connect to the dots and then look to the=0D=
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SI and EMC guys to make the board work.  ps. we work well together cuz=0D=
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the only dots I connect are in my granddaughters coloring book.=0D=0A
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  So given the dearth of details here's one answer (of many) he can use;=0D=
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  50 ohm surface traces (no vias), spaced 5 times the distance to the=0D=0A
reference plane, no breaks in the plane below the traces, matched=0D=0A
lengths to within 1 mil. (my layout guys can do that in about 30 seconds=0D=
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all day, another "cute trick"), and all added parts are absolute mirrow=0D=
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symmetric (the parts might need vias).  =0D=0A
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