TPS23861+TPS279 for 60w design

Hi William,

I believe you are referring to some high power Phihong PSE's. When using a 12.5k detection resistor, it will power up to high power regardless of class.

For the TPS23861, you can do two things for 60W (at the PSE) application. One is forced UPOE which is described in the app note below using two TPS2378.  This only requires using two ports of the TPS23861 is automode. You can use the TPS23861EVM. It contains two RJ45 connectors for 4 pair high power solutions.

http://www.ti.com/general/docs/lit/getliterature.tsp?baseLiteratureNumber=slva625&fileType=pdf

Or you can operate the GUI to manually turn on ports and change current limits as necessary to provide 4 pair high power.

We can work offline to discuss this.

Hello William and Darwin,

I am afraid I am facing a similar issue. I designed a PSE based on TPS23861 kit (but discarded all 2 pairs ports and kept only one 4 pairs port), and tested it connected to TPS2379 kit. My intention is to use Ultra PoE standard, feeding PD through all 4 pairs.

I succeeded in feeding TPS2379 through 2 pairs, setting commands in PI Commander s/w, but not in all 4 pairs simultaneously.

First I reached class 5 state for both ports 1 and 2 (I used ports 1 and 2 of TPS23861, and discarded remaning ports in my design) in semiauto mode, but in the next step, when I set Power Enable (PWON) in PI Commander for both ports 1 and 2 simultaneously, only one out of the two ports powers up, and the other port goes to detection with invalid PD state waveform. The port powered up is not always the same, it seems to be a random choice.

I wonder if I must check hardware again, or follow a different setting sequence.

Could you help me?

Best wishes,

Hi Newton,

Typically for this application, one port is turn on at a time. The first to turn and startup the load (micro). Then the communication between the PD and PSE through the data line occurs in which the PD and PSE interact to turn on the second port and raise the current limit.

Hello Darwin,

I tried to activate port 2 after port 1 turned on, but PD turned off.

After port 1 turns on and goes to class 5, completing classification, I set manual mode and try to set PWON on port 2. But ports 1 and 2 go to unknown state, TPS2379 kit turns off and 2 flags change:

Power Good Status Change
Power Enable Status Change

Is there another sequence to use, or maybe some alarm is activating due to hardware issue?

Best wishes,

Hi Newton,

Is there load on the output? There should be some load (at least 10mA) to keep the first port on.
Also, is the "poe plus" boxes checked in the GUI?

Hi Darwin,

Thank you very much for the tip, it worked fine.

Best wishes,