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TPS2663: About the current limit function of TPS26631

watanabe.seiji
Prodigy 40 points
Part Number: TPS2663

Dear TI support team,

I have a question about the current limint during the start up of TPS26631.
I know that PGOOD will be Low until VIN = VOUT and IOUT will be limited IOL during start up. But I saw that the inrush current(I_IN) exceeded IOL at the startup start point and it took a little time to be limited to IOL. (IOUT may exceed IOL during start up in our system if there is no limit.)
I want to know that maximum current at start up point, and how long will IOUT take for being limited to IOL. Could you tell me those?

Thanks

Best regards,

Watanbe

  • 0
    TI__Guru** 105361 points

    Hi Watanbe,

    The typical response time of current limit loop is 30us. 

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Prodigy 40 points

    Hi, Rakesh

    Thank you for your replay.

    What is the maximum response time of current limit loop?

    According to our measurements(R_ILIM=7.5kΩ), it looks longer than 30us.

    Also, does the maximum value of the current flowing during that time depend on the system?

    Best regards,

    Watanbe

  • 0 in reply to watanabe.seiji
    TI__Guru** 105361 points

    Hi Watanbe,

    30us is a typ design spec. 

    The current limit has +/-7% variation. As long as it is with in +/-7% of your set current limit value, it should not matter much.

    may we understand why it is important. ?

    Best Regards,

    Rakesh

  • +1 in reply to Rakesh
    Prodigy 40 points

    Thanks Rakesh.

    may we understand why it is important.?

    → Because we want to determine the maximum value of the inrush current of the system.

    Please let me know the following two questions.

    (1) Do you know the max spec of the response time of the current limit loop?

    (2) Does that mean that the instantaneous current value before the response time of the current limit loop (the red part of the waveform above) is also within ±7% of the current limit value?

    Best regards, Watanabe

  • 0 in reply to watanabe.seiji
    TI__Guru** 105361 points

    Hi Watanbe,

    Inrush current can be controlled by Cdvdt cap on  dVdT pin.

    We don't characterize the response time of the current limit loop. so, we don't have the max spec

    The current can exceed +/-7% of the current limit value before the current limit loop starts acting. I am just pointing to your test waveform 

    Best Regards,

    Rakesh