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

Randolph, I suggest any of the following four books would be helpful to y=
ou:

Signal Integrity Simplified, Bogatin
High Speed Signal Propagation, Johnson and Graham
Digital Techniques for High Speed Design, Granberg
Right the First Time Vol II, Ritchey

Lee Ritchey self publishes so if you want Right the First Time  you will =

need to go to www.speedingedge.com.  Your alternative is to rely on PHY=20
manufacturer guidelines.

The basic guide that I can offer you is this:

* Loosely coupled pairs are easier to manage than tightly coupled=20
pairs.  If you don't specifically need tight coupling for density=20
reasons, you will be less likely to go wrong with loosely coupled pairs. =


* The crude approximation for a loosely coupled pair is Zodd =3D 2*Zeven.=
 =20
Ie two loosely coupled 50 ohm traces will have about a 100ohm odd mode=20
impedance.=20

* Maintaining a uniform impedance and matched electrical length will do=20
much to get you were you need to go.  If you are a tiny bit sloppy, it=20
shouldn't matter for a student project.  Your project doesn't have to=20
pass FCC part B, and it is unlikely that you have to support maximal=20
length links.

Eric Bogatin's book has some impedance nomographs.  However, there are a =

number of free calculators around some better than others.  Google for=20
impedance calculator and take your pick.=20

Good luck.

Steve.



Randolph Voorhies wrote:
> Hi Everyone,
>    I'm brand new not just to this list, but to the world of PCB product=
ion in general.  I'm currently a masters student at USC in robotics and h=
ave been producing some relatively simple PCBs for the past few months us=
ing Eagle. I'm now working on a fairly complex project that involves crea=
ting a custom baseboard for an XTX module (xtx-standard.org).  My formal =
training is in digital electronics, computer architecture, and computer s=
cience, so when it comes to signal integrity I'm pretty much at a loss.  =
Does anyone know where to find specific routing guidlines for differentia=
l pair lines such as firewire and ethernet? I have read all sorts of conf=
licting advice (differential impedence is crucial vs. differential impede=
nce couldn't matter less, etc..), and have had a very difficult time find=
ing exact numbers for trace spacing/individual trace impedence and so on.=
 If anyone with experience has any advice that has worked for them it wou=
ld be very very very much appreciated.
>
> Thanks so much,
>   Rand Voorhies
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