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Ethernet LAN PHY termination

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DesgEng

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hi,

i'm working on ethernet for first time and using a industrial M12 connector instead of RJ45. I'm also using a 75ohm termination resistor along with 2KV capacitor. Wanted to know if 0.5W 75ohm resistor is sufficient and also any calculations related to termination resistor calculation is required.

Thanks in advance
 

It's unclear, which termination your refering to. The signal pairs (RX/TX) have to be terminated at the PHY chip, after
passing the ethernet transformer. Or do you mean termination of unused cable pairs?
 

Hi,
Thanks for quick reply. I was referring to CM termination resistor (75ohm with a high voltage capacitors after the Magnetics.) Please refer the attached file Page 9.
Thanks
 

These are basically small signal components. I don't see a specification for termination resistors assembled to integrated
magnetics ethernet jacks, but I would rather expect 0.25 than 0.5 W. Of course, you are able to damage them, e.g. by
connecting a PoE hub or indirect lightning influences.
 

    DesgEng

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Thank you very much for the information provided.

Added after 5 hours 58 minutes:

Hi,

I've one more question related to Ethernet protection. I've a requirement of 16KV injected on M12 connector(used instead of RJ45) pins. and battery protection(Battery voltage: 16.2V to 72V).
Ist a good practice to use a PTC fuse and transil for transient protection. But the switching speed of PTC would be a concern i believe. I'm using LAN8700 PHY with H1102NL MAG.
My understanding is MAG will saturate under under high loads and protect the PHY. Please correct me.

Thanks.
 

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