[SI-LIST] Re: gigabit ethernet trace length

The 2KV isolation goal is easy to meet.  Just route the signals on layer 2
or below and you have it.  All common dielectrics used in PCBs have a
voltage rating of at least 1KV per mil of thickness.  Rarely is a laminate
layer between signal and plane less than 4 mils.  You can even meet this
goal on the surface by making sure that neighboring circuits on the outer
layers are at least 2 mm away.


> [Original Message]
> From: Thompson, Gary D \(Gary\) <Gary@xxxxxxxxx>
> To: Peterson, James F \(FL51\) <james.f.peterson@xxxxxxxxxxxxx>;
<si-list@xxxxxxxxxxxxx>
> Date: 5/30/2006 3:38:47 PM
> Subject: [SI-LIST] Re: gigabit ethernet trace length
>
> Just keep in mind that part of the Ethernet spec includes 2KV isolation
> (one of the reasons for the transformer, after all). If you can keep the
> isolation region in tact for 6-8", there's no reason it won't work.
>
>
>
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>
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> =3D=3D=3D=3D=3D=3D=3D=3D
> Gary Thompson                        Phone: (512) 821-6521
> Systems/Applications Engineering       FAX: (512) 821-6810
> Agere Systems                       Mobile: (512) 751-8115
> Multi-Service Networking Division    Email: gary@xxxxxxxxx
>
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>
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> =3D=3D=3D=3D=3D=3D=3D=3D
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Lee Ritchey
> Sent: Tuesday, May 30, 2006 2:49 PM
> To: Peterson, James F (FL51); si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: gigabit ethernet trace length
>
>
> Not a problem, works just fine.  Don't know what might be behind the
> restriction someone put on you.
>
>
> > [Original Message]
> > From: Peterson, James F \(FL51\) <james.f.peterson@xxxxxxxxxxxxx>
> > To: <si-list@xxxxxxxxxxxxx>
> > Date: 5/30/2006 11:59:01 AM
> > Subject: [SI-LIST] gigabit ethernet trace length
> >
> > greetings,
> >
> > In a 1000BaseT Ethernet circuit, I would like to extend the distance=20
> > between the magnetics and the RJ-45 connector to about 6 to 8 inches=20
> > (including good SI practice : ref planes, controlled Z, matched=20
> > lengths, etc.). Everything I read says that you can't do that, that it
>
> > must be less than an inch, but I don't understand why. Can someone=20
> > explain?
> >
> > thanks -
> > Jim Peterson
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