[SI-LIST] Re: RJ-45 Connector
- From: Zhangkun <zhang_kun@xxxxxxxxxx>
- To: joel@xxxxxxxxxx, leeritchey@xxxxxxxxxxxxx
- Date: Sun, 11 Jun 2006 11:04:19 +0800
Dear Joel
As to my experience, whether cutting the plane under RJ45 or not depends on the
frequency and the system. The purpose of this action is to avoid EMI. I
remember that there was some useful comment in "Noise Reduction Techniques".
Best Regards
Zhangkun
2006.6.11
----- Original Message -----
From: "Joel Brown" <joel@xxxxxxxxxx>
To: <leeritchey@xxxxxxxxxxxxx>
Cc: "Curt McNamara" <CurtM@xxxxxxxxxxx>; "Chandupcb" <chandupcb@xxxxxxxxx>;
<si-list@xxxxxxxxxxxxx>
Sent: Saturday, June 10, 2006 12:45 AM
Subject: [SI-LIST] Re: RJ-45 Connector
> My understanding from a question I previously posted was that the board
> ground should not go past the Ethernet magnetics for fear that common mode
> noise would couple from the board ground to the RJ45 side of the magnetics
> and radiate out on the Ethernet cable.
> It was suggested that the area under the RJ45 should be connected to chassis
> ground with a split between chassis ground and board ground. This was
> recommended in an Intel app note, but our EMI consultant said it was wrong
> and recommended we run the board ground under the RJ45 with no plane split
> and also to connect the RJ45 shield to chassis ground.
> Joel
>
> Lee Ritchey wrote: Curt, The creepage distance is on the surface, not
> internally. The internal spec is 1700 VDC withstanding and that is achieved
> with only 2 mils of FR-4. So, there is no need to clear planes that are
> internal to the PCB. Why do engineers globally apply specs, when they don't
> apply? Yes, there is one regulator person in Australia who does not
> understand this and insists that planes need to be cleared. He is out to
> lunch! We solved the problem by just not shipping to Australia! The whole
> market in Australia is less than half of Californina, so it wasn't much of a
> sacrifice. [Original Message] From: Curt McNamara <CurtM@xxxxxxxxxxx>[1] To:
> <leeritchey@xxxxxxxxxxxxx>[2]; Chandupcb <chandupcb@xxxxxxxxx>[3];
> <si-list@xxxxxxxxxxxxx>[4] Date: 6/9/2006 9:10:42 AM Subject: [SI-LIST] Re:
> RJ-45 Connector From a safety standpoint the "line side" of the RJ45 can be
> TNV (tele-communications network voltages). These wires can go through
> wiringcabinets where a single fault could short them to AC (Ethernet), or
> could go on poles outside the building (DSL or modem). As a result approval
> bodies require a transformer for isolation between TNV and SELV. To ensure
> the isolation, you need to keep minimum distances (called creepage and
> clearance) between these line side signals and anything on the SELV (safety
> extra low voltage) side. In practice this requires there be no planes under
> the output side, since the distance between the planes and the output traces
> or pins would violate the standard. You should check with your approvals
> bodyto ensure that the correct standard is being applied. Curt Curt
> McNamara.P.E.=20 Senior Electrical Engineer=20 Logic Product Development=20
> 411 Washington Ave. N Suite 101=20 Minneapolis, MN 55401=20 Tel
> 612-436-5178=20 Fax 612-672-0443=20 curtm@xxxxxxxxxxx=20[5]
> www.logicpd.com=20[6] This message (including any attachments) contains
> confidential information intended for a specific individual and purpose, and
> is protected by law. If you are not the intended recipient, you should
> deletethis message and are hereby notified that any disclosure, copying, or
> distribution of this message, or the taking of any action based on it, is
> strictly prohibited. -----Original Message----- From:
> si-list-bounce@xxxxxxxxxxxxx[7] [mailto:si-list-bounce@xxxxxxxxxxxxx[8]] On
> Behalf Of Lee Ritchey Sent: Friday, June 09, 2006 11:00 AM To: Chandupcb;
> si-list@xxxxxxxxxxxxx[9] Subject: [SI-LIST] Re: RJ-45 Connector Chandu,
> Thereis no valid reason to do this. Rules like this are often called
> elephantrepellant. [Original Message] From: Chandupcb
> <chandupcb@xxxxxxxxx>[10]To: <si-list@xxxxxxxxxxxxx>[11] Date: 6/9/2006
> 3:46:00 AM Subject: [SI-LIST] RJ-45 Connector Hi Gurus, May I know why will
> we remove the Plane under the RJ-45=20 connector.Some times only chasis gnd
> is Allowed under the connector. Why? Regards Chandu
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