• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 64 subscribers
  • Views 327 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.

TPS23730: Advanced Adapter ORing - Option 3, Adapter Priority, Synchronous Rectifiers Clarifications

Samer Musa
Prodigy 10 points
Part Number: TPS23730
Other Parts Discussed in Thread: TPS23753

Hello,

I am working on a new design and intend to use TPS23730 as my PoE PD chip. External power adapter is also used to provide power to the board in case of no Ethernet PoE is plugged in.

Priority is given to the power adapter in case both are available (adapter and Ethernet PoE).

I did go over your Application Report SLVA306A "Advanced Adapter ORing Solutions using the TPS23753" document, in particular for Section "3.5 Option 3, Adapter Priority" on page 13 I did not understand the part that talks about synchronous rectifiers problem, highlighted in the attachment below,

Can you please talk a little bit more about the problem and how to disable the rectifier?.

BTW, this comments is also mentioned in section 3.4 in the same document.

Thanks.

  • 0
    TI__Mastermind 21320 points

    Hello,

    The problem is described in section 3.4:

    A MOSFET can allow power to flow in the opposite direction, so you need to prevent this from happening with a diode or a output blocking MOSFET. 

    Alternatively, you can use a Power multiplexor and program the priority you want. That would be my suggestion for a synchronous output. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    Prodigy 10 points

    Hello,

    I did refer to section 3.4 in my question, but it is still not clear to me the turn off needs to happen.

    Could you please explain a little bit more in details with diagrams if possible, thank you.

  • +1 in reply to Samer Musa
    TI__Mastermind 21320 points

    You do not want your adapter backdriving your design -- sending power from the secondary side of the transformer to the primary side. That could cause damage and unpredictable behavior. 

    Because MOSFETs can be turned on and allow current to flow the other way, you need to be careful to ensure this does not happen. This does not happen with diodes since diodes always block reverse current and cannot be accidentally turned on in this architecture. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    Prodigy 10 points

    Thank you for your help