I have a schematic of Ethernet Transformer that supports POE, and 2.5GBT. I plan on using Ethernet with transformer on my PCB to connect to Network Switch.

Are pin VC12 13, VC36 14, VC45 15, VC78 16 DC signal? Where do this pins connect to ?

What about TRCT1, TRCT 2, TRCT, 3, TRCT 4? Where are they connected to?

Also, what is common mode filter that is displayed on the schematic. I have heard that ethernet with transformer are used for isolation. Can anyone explain what does the mean?

What else do I need to know before using the Ethernet with Transformer.

Any help is appreciated.

enter image description here


If you don't want to receive power from the switch -- leave this pins disconnected;

If you want to -- you need PoE-unit, which receives power from these pins, and converts PoE voltage level to 12V or so.

You heard right -- transformer used for isolation. So your PoE unit should have isolation too. It means that it will also have it's own transformer inside for that.

  • \$\begingroup\$ What about TRCT1, TRCT 2, TRCT, 3, TRCT 4? Where are they connected to? \$\endgroup\$ – Kasap23 Nov 21 '19 at 23:28
  • \$\begingroup\$ TRCTn depend on PHY you are using. They might be not connected, or they might be decoupled to GND with 0.1uF or so. \$\endgroup\$ – Alex Life Nov 21 '19 at 23:44
  • \$\begingroup\$ I just found out that I have a PHY less network switch. \$\endgroup\$ – Kasap23 Nov 22 '19 at 0:27
  • \$\begingroup\$ It doesn't matter what switch is consist of. I am talking about PHY in your design. \$\endgroup\$ – Alex Life Nov 22 '19 at 22:57

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