[SI-LIST] Re: Gigabit ethernet placing and routing related question
- From: "Stefan Milnor" <stefan.milnor@xxxxxxxxxxxxxx>
- To: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>, "Peter zhu" <yonghui.sky@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>, <jhasson@xxxxxxxxxxxxxxxxxxx>
- Date: Sun, 31 Oct 2010 12:04:24 -0700
Chassis GND: the potential that your chassis is at
________________________________
From: si-list-bounce@xxxxxxxxxxxxx on behalf of Lee Ritchey
Sent: Sun 10/31/2010 9:52 AM
To: Peter zhu; si-list@xxxxxxxxxxxxx; jhasson@xxxxxxxxxxxxxxxxxxx
Subject: [SI-LIST] Re: Gigabit ethernet placing and routing related question
There is not such thing as "chassis ground". What is really meant by this
statement?
> [Original Message]
> From: Peter zhu <yonghui.sky@xxxxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>; <jhasson@xxxxxxxxxxxxxxxxxxx>
> Date: 10/30/2010 2:11:00 AM
> Subject: [SI-LIST] Re: Gigabit ethernet placing and routing related
question
>
> PHY output is analog signals, so keep them as short as possible.
> The trace between PHY and transformer refers to signal GND, and the trace
between PHY and connector is chassis GND or Earth. So you have to cut the
ground plane.
> Now there are so many RJ45 integrated transformer, this will keep
transformer and connector very close. Why not use such RJ45?
> I have not seen separate CM choke, it is always the part of transformer.
> Another is keeping center tap power very clean, otherwise it will have
Ethernet emission issue.
> Peter zhu
>
>
>
>
>
> --------------------------------------------------
> From: <jhasson@xxxxxxxxxxxxxxxxxxx>
> Sent: Thursday, October 28, 2010 4:57 AM
> To: <si-list@xxxxxxxxxxxxx>
> Subject: [SI-LIST] Gigabit ethernet placing and routing related question
>
> > Hi,
> > I am currently working on a project involving routing of gigabit
ethernet
> > signals between a PHY and the outside world. Basically, after going
> > through the routing recommendations, it is most of the time recommended
to
> > have the PHY close to the magnetics close to the RJ45 connector. The
> > closer the better.
> > I went though the si-list about this subject and I found some advice
like
> > the transformer should be close to the phy but the CM choke should be
> > close to the connector. The idea of having an EMI protection device
close
> > to the connector seems to make sense but I do not understand the reason
> > why the transformer should be close to the PHY : what is the advantage
> > versus having both the magnetics and the CM choke near the connector
and
> > therefore a "long" distance between the PHY and the magnetics ?
> > Although having the CM choke near the connector seems to make sense I
have
> > also read about the fact that it it was ok to have quite a distance
> > between the transformer/choke and the connector but no mention there
about
> > some restrictions concerning the PHY to transformer distance.
> > Could someone, give (again ?) some insights into the pros and cons of
each
> > topology ?
> >
> > Best regards,
> >
> > JF Hasson
> >
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