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Original question:

TPS65911: Inductor and Rtrip of VDDctrl

TPS65911: VDDCtrl current limit by RTRIP Resistor

Dice-K
Mastermind 6440 points
Part Number: TPS65911

Hi support team,
Continuing from the "Original question" above.

Is the VDDCtrl current limit by RTRIP Resistor detected by the Low Side Valley current?

In that case, I think that "(IOUTmax - inductor-ripple-current/2)" is required for the calculation of equation (3), not "IOUTmax".
However, since there is no margin at all with this method, are you calculating with "IOUTmax" for convenience?

Regards,
Dice-K

  • 0
    TI__Genius 16525 points

    Hi Dice-K,

    I believe the IOUTmax is related to the equation I found in this application note: Know Your Limits

    From page 8:

    In general, the valley current and the IOUTmax are similar since the second term in this equation is usually small but It looks like IOUTmax already takes into account the valley current.

    Regards,

    James

  • 0 in reply to James Steenbock
    Mastermind 6440 points

    Hi James,
    Thank you for your reply.

    IVALLEY = IOUTmax - inductor-ripple-current/2
    The above equation is the same as the following equation (2).


    Since "inductor-ripple-current/2" is small,
    IOUTmax ≒ IVALLEY
    As such, does the equation (3) in the datasheet hold true?

    Best regards,
    Dice-K

  • +1 in reply to Dice-K
    TI__Genius 16525 points

    Hi Dice-K,

    Yes, I believe this is why IOUTmax was used is equation (3) in the datasheet. You should be able to use that equation for the RTRIP calculation without significant error since the terms aren't too far apart.

    Regards,

    James