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 ?
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 ?
@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.
@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?