WIZnet Developer Forum

W5500 And POE RJ45 without RCT and TCT

Hi, I have used W5500 with HR911105A RJ45 connector. this connector has both TCT and RCT pins so I used this schematic and it works perfect.

Now I would like to use an POE RJ45 but some of them do not have TCT and RCT pins! they just have CDT pin! (for example 7499410213) , I do not know how should I change the schematic for that. could you please guide me about it ?

and shall I use PoE POWERED DEVICE CONTROLLERS IC (for example TPS2375) for this RJ45 or not ?

Thanks in advance

could you please guide me about it ?

I am afraid you will need to find jack with separate TCT and TCR because W5500 is having one pulled up, and another not DC-biased. Or you may look at the W5100s (both not DC-biased) or W5100 (both DC-biased to 3.3V), its both RCT and TCT are pulled up, so using common CDT would be ok.

shall I use PoE POWERED DEVICE CONTROLLERS IC (for example TPS2375) for this RJ45 or not ?

Would it better asking this at TI forums?

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Thank you for guiding me. so I have to use an RJ45 with TCT and RCT because I should use W5500.

about the PoE POWERED DEVICE CONTROLLERS IC, I just want to know, is it necessary to use this kind of ICs or not ?

@Eugeny : No, that is not correct.
If TCT and RCT are internally connected inside the MagJack you can still use the W5500 !
Yes, you need to disconnect the CT signal from the centerpoint between the RX signals.
The problem with connected CT is the offset voltage.
But with the two 6n8 capacitors in the rx signal, this RX is AC coupled and the DC offcet is eliminated.

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@4jochen why then complicating things in the first place separating TCT and RCT in the main reference circuit diagram, and not connecting both of them to 3V3?

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