PoE ethernet magnetics.

Should be designed to handle the DC common mode current without affecting data transmission. Note that, while some data transformers are symmetrical, with interchangeable pri and sec, POE transformers usually have non-interchangeable pri/sec. Sometimes, it's not easy to determine which way to use them, and some app notes get this wrong. Paul Mathews

Do they employ some kind of capacitive coupling to eliminate DC? I thought the difference was in the capability handle large currents uA vs mA. Would it be a serious problem to use non-PoE magnetics in a PoE application ..?

Many shops includeing digikey seems not to stock. And pulseeng seems to got just about anything I want in magnetics..

magnetics..?

In USA, POE xfrmrs are readily available from Pulse, Datatronics, and Xfmrs, Inc. I don't know what the situation is elsewhere, but the parts are made in China, in any case. It's not capacitive coupling at all...just core and winding design. Paul Mathews

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Problem is Digikey doesn't stock them. PulseEng etc.. will only send samples. If you order from them you must do so in 1k+ quantities.

How could PoE magnetics be better than normal magnetics in handleing common mode current..?

The magnetics might tolerate more flux before they saturate, thus allowing data transmission to take place through the magnetics while the DC current is being supplied.

-- Mike --

This is interesting, POE generally does not use the TX and RX pairs in the Cat 5x. It uses the un-used pairs. But I suspect the DC biasing may be a key point, or just marketing hype.

Cheers

PoE as per IEEE 802.3af in 10Base-T/100Base-TX may use mode A 12 + 36 or mode B 45+78 as decided by the Power Sourceing Equipment. And for 802.3af with 1000Base-T it must use the same pairs. So PoE capable magnetics is a neccesity to be standards complient. Not just a marketing hype. However it might be that margins on ordinary magnetics for flux saturation is ok, who knows ;)

mA.

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See earlier post. Pulse isn't the only source. I suggest contacting Xfmrs, Inc next. Various techniques are used to improve tolerance for DC, including larger cores, air gaps, different materials. The magnetics designers might be willing to discuss it, if you really must know.