• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 474 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS2375: Designed 13 Watt PoE using TPS2375 - But I Need Isolation, As In Isolation Transformer? Not Very Clear From Datasheet

Matt Roybal
Intellectual 345 points
Part Number: TPS2375

Hello, I am needing to create a 13 watt PoE power source, which eventually provides a 12VDC power rail to the PCB. I attached the schematic I currently implemented (see below).

The problem with this is that I need isolation, since the device will have some connectors/plugs accessable to the end user. I am under the impression that the transformer/magnetics inside the RJ45 is not enough, and that I am supposed to put an isolation transformer in the mix, such as part number "POE13P-12" from coilcraft. The datasheet doesn't mention how to connect up a transformer. I don't think it matters if its flyback or forward transformer, I just simply need the isolation is all, but I can't find any information on this. I don't really know what I need to do here. Any help or advice is greatly appreciated.

And for reference, this is the RJ45 port I am using just in case that is needed: "HR873173A" from HanRun. It has magnetics built into the port.

  • 0
    TI__Mastermind 37071 points

    Hi Matt,

    Thanks for reaching out!

    I would assume the transformer you mentioned "inside the RJ45" is the data transformer as shown below. It won't isolate the power.

    If you want a galvanic isolation for the power, you can build a flyback converter after the TPS2375's VDD and RTN. Also please use TPS2375's "PG" pin to enable this flyback circuit. Let me know if you have any further questions. 

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    Intellectual 345 points

    Hi Diang, thank you for the response! Yes that was exactly what I was referring to - the data transformer. Ok so yes I definately need the galvanic isolation solution.

    I thought the appropriate transformer that I needed was "POE13P-12" from coil-craft. But I don't see any reference documentation on how to build the flyback converter. The datasheet for TPS2375 does not have any information on this. Is there another reference I can use to connect up an isolation transformer to this, and like you said use the PG pin to enable it? I am reading that it gets complicated, needs impedance matching, etc. otherwise the transformer will be noisy, so I figured there would be a reference somewhere that I can build?

  • 0 in reply to Matt Roybal
    TI__Mastermind 37071 points

    Hi Matt,

    Got it! Sorry that I did not find a TPS2375 reference design with isolated converter.

    Here is two flyback boards you can refer: 

    13-W rated flyabck, TPS23753A based. You can refer the power MOSFET / flyback transformer selection. Besides, you can also use TPS23753A which is AF PD controller + PWM controller; TPS2375 is AF PD controller only.

    https://www.ti.com/tool/PMP8803

    25.5-W rated flyabck, TPS2376H based. You can refer the PG pin connection and the DC/DC controller IC

    https://www.ti.com/lit/ug/slvu197b/slvu197b.pdf

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    TI__Mastermind 37071 points

    Hi Matt,

    I will close this thread for now. Please reply or open a new thread if you have further questions.

    Best regards,

    Diang