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Ethernet shield connecting, where to put...

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mondoemme

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Dear all,

I am developing a board with ethernet "on-board" (PHY+transf).
Due to size constraint I cannot mount an RJ45 connector on the pcb but I have to
connect the TX+-, RX+- signal with four wires that go from the board and connect them with a twisted pair cable (shielded).

From above, one question arise: where and how can I connect the shield?
Is enough to connect the shield on the other side of the ling, for example a PC?
Any hints?

Thanks in advance.

M
 

You should connect the shield to a protective ground (e.g. metallic enclosure), possibly through a DC blocking capacitor.
 

Is it a requirement that you have shielded cable, emc etc. Normally this is used for connection between shielded sockets, ultimately grounded at the hub. Its balanced line, so possibly no reason for a shield, unless as above.
 

Hi to all,

so, if I well understand, it is right to connect the the 4 wires coming from the board without shield to a connector located in the metallic enclosure (about 3-4 inches of distance), and then connect the shielded cable (about 50 feet) that reach the connector from a shielded hub.
The connector above has a gnd pin and it is connected to the enclsoure.

Thanks a lot



PS.
The need for a shielded cable is a project contraint due to the extermely noise environment in which the board will run.
 

Do not think that that would be a problem. You could always wrap foil round the wires later if needed, then wrap a bare wire round it to connect to ground. Unlikely you would need to do this though. Differential signaling is quite resilient to noise, as there is no ground referenced signal. Even data networks using unscreened cat5 in electrically noisy factories, do not seem to have a problem. I would go ahead with what you propose.
 

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