I want to implement a PoE solution and I started to design the board based on W5500 reference designs:
[url]http://wizwiki.net/wiki/doku.php?id=products:w5500:refschematic[/url]
I am using the design with the external transformer.
My questions are:
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How to adapt the schematic to use 2 pairs for PoE and be compatible with both modes of PoE? In DFRobot’s Ethernet shield
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(see schematic at bottom of page), the pairs were filtered with an C-R-C network, but, correlating with W5500’s schematic, should these components support 2kV? Also, for me it is not clear if DFRobot’s design works in both modes of PoE. -
I’ve seen RJ45 jacks with integrated magnetics and WIZnet gives a separate reference design which uses this type of jack. Can that design be adjusted for PoE? How?
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I’ve found many types of jacks which integrates PoE magnetics such as:
MagJack SI-52008-F
[url]http://belfuse.com/pdfs/SI-52008-F.pdf[/url]
Wurth 7499210121A
[url]https://katalog.we-online.de/pbs/datasheet/7499210121A.pdf[/url]
Why do some jacks, like Wurth, integrate diode bridges when PoE is DC? Also, see Silvertel’s PoE 9600 module which integrates diode bridges.
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In the schematic from DFRobot, a PoE PD interface and regulator circuit is used. Can’t I just take the 48 V DC and use that voltage in a simple DC-DC converter? Why does such an interface is required?
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Would it be better to use a jack with metallic enclosure, than a plastic one?
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Would the PoE design work if I used a lower voltage, 5-12 V, instead of 48V?
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Relating to the WIZnet designs, why does the center tap on the TX transformer, on the chip side, needs to be connected to 3.3V?
Thank you!