I am trying to create a PCB containing a PIC18F66J60. I want to power the board using POE. For the POE i plan to use the TPS2375PW.

The two IC's have two quite different refferent schematics in their datassheets: PIC18: enter image description here

TPS2375PW: enter image description here

I plan on just using the center tap on the TW MCU side, and connect it as the PIC18 datasheet says I should.

However, the center taps of the are connected in two different ways, in the two schematics. As the resistors and capacitor connected on the PIC18 schematic, is just for EMC purpose (as per the datasheet), I would just have used the TPS2375PW schematic, but the PIC18 datasheet states "Power over Ethernet applications require capacitors in series with these resistors." refering to the 75 ohm resistors.

From this I get that the pic18 expects these resistors, also for POE applications.

How would i combine these two IC's for an POE application. Or is it not possible?

  • 1
    \$\begingroup\$ Microchip themselves have PoE front ends in their portfolio (the PoE parts came with SMSC and Micrel acquisitions, I think). Perhaps you can find more app notes and reference designs there. \$\endgroup\$ Sep 19, 2021 at 19:27
  • 1
    \$\begingroup\$ What magjack are you using? You require capacitors in series otherwise the 75Ohm resistors will draw POE current - you don’t want that. Besides, the PIC doesn’t require those resistors as they’re for earth bonding. Why are you using a PIC18 with ethernet in this day and age? There are better parts available. \$\endgroup\$
    – Kartman
    Sep 19, 2021 at 23:31

1 Answer 1


Of course it is possible.

The PIC schematics show how it would work in general with standard Ethernet, as it does not support POE at all.

The TPS2375 schematics show what changes are needed to add POE support. You still need to connect the PIC to the Ethernet lines as it only shows how to add the power part.

The 75 ohm resistors just need capacitors in series to allow for POE.They are not drawn in the TPS2375 schematics as it is simplified away, it focuses on getting power, and for that the Ethernet data is not relevant.


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