• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 62 subscribers
  • Views 146 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TPS23751: Dual Input Redundant Type2 Power Application

Allan Fan
Expert 5430 points
Part Number: TPS23751
Other Parts Discussed in Thread: PMP20859, TPS23731

Hi team,

I know we have reference designs with two PD solutions for dual inputs redundant application but wondering if somehow it's feasible to use just one PD or what are the concerns/challenges? For example, customer plan to use one TPS23751 for dual input, redundant, type2 power application.   They do actually tried this condition with one TPS23751 and sometime it works but sometimes failed.  

Thanks,

Allan

  • 0
    TI__Mastermind 21320 points

    Hey Allan, 

    There are two main approaches to redundancy  and smooth transitions. The first is having two DCDC's, two PD's, and then an adapter on the secondary side. This is typically the easiest implementation since it is just combining two "normal" PoE designs at the output. If the design is a diode flyback then the outputs can simply be tied together. If not, then we can use a power MUX to provide that smooth transition of power. 

    The other approach is to use two PD's with one DCDC, and then an adapter on the input. This design requires more circuitry to achieve. We created a blog post, training video, and reference design on this topic. The key with this approach is a standalone PD is required --- so the TPS23751 would not work here. Additionally Auto-MPS is required for this, which the TPS23751 does not have.

    Now the PMP20859 approach can be used with one port instead of two, and still provide the smooth transition between Adapter and PoE. A part with Auto-MPS is still required, however. The direct replacement would be the TPS23731. 

    For a dual input, Type 2 application, I would recommend the TPS2372-3 and pair it with a Type 2 DCDC. Essentially following PMP20859 but changing schematic page 3 for a 25W DCDC. 

    Let me know if you have any questions!

    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
    TI__Expert 5430 points

    Hi Michael,

    Customer would like to know considerations if just using single one PD+ DCDC for dual inputs. I saw the training video that learnt one reason may fail using single PD+DCDC is because when second PSE is plugged in that it should wait 80 ms before providing power to the DCDC load. So if this is the case, the second PSE will crash. Is my understanding correct? Are there any other challenges so we can't use single PD+DCDC for dual inputs?

    Regards,

    Allan

  • 0 in reply to Allan Fan
    TI__Mastermind 21320 points

    Hey Allan, 

    Well once one of the PSE's powers up, the other PSE sees the 48V and will not power up the device. So we need two separate PD's to negotiate power if we want redundancy. 

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

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments