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 ?
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