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TPS2373: Questions about bulk cap

David Kim2
Genius 3305 points
Part Number: TPS2373

Hi

The contents below are in DATASHET P.23 of TPS2374.

When I tested the contents below, I'm not satisfied if I don't reduce the BUCK CAP(C9,C11,C41) capacity.


Can the output CAP satisfy the contents below with 300uF?
If there is a way, can you tell me how to do it

Thanks

  • 0
    TI__Mastermind 37101 points

    Hi David,

    Thanks for reaching out.

    Sorry that I am taking a sick leave and probably I can return in April 1st. I will get back to you after that. 

    Best regards,

    Diang

  • 0 in reply to Diang Xing
    Genius 3305 points

    Hi Diang

    This is a gentle remind.

    Thanks

  • 0 in reply to David Kim2
    TI__Mastermind 37101 points

    Hi David,

    Thanks for your patience.

    300 uF looks very high for PoE application thus during the PD inrush period. TPS2373-4 has 275 mA lowest inrush current. 57V * 300uF / 275mA = 62 ms which is longest inrush time needed.   

    According to the standard, PDs shall draw less than IInrush_PD and IInrush_PD-2P from TInrush_PD max until Tdelay min, when connected to a source that meets the requirements of 145.2.10.7. In this condition. 62 ms should be an ok value. 

    The recommended bulk cap value in PoE PD application is shown below:

    Power                  Bulk Cap

    13W                      10-22uF

    25W                      33-47uF

    50W                      68-100uF

    70W                      100uF-200uF

    Best regards,

    Diang