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Original question:

TPS40211: How to set output voltage for LED driver.

TPS40211: About external soft-start capacitor

Tsukui Yusuke
Guru 21930 points
Part Number: TPS40211

Hi,

Customers want the soft start time to be as long as possible.
However, there is no information about the maximum value in the data sheet.



Could you tell me the recommended maximum value of the soft-start capacitor?
And Please tell me the precautions when the soft start time is made extremely long.

Regards,
Yusuke




  • 0
    TI__Guru 61325 points

    Hello Tsukui,

    Why does the customer want to extend the softstart time to an extreme? Is there possibly a better way to solve the problem the customer wants to solve?

    In general we do not recommend to use extreme values for the SS cap, as then the startup can get extremely noise sensitive. At the moment I do not have an exact number for the SS cap.

  • 0 in reply to Brigitte
    Guru 21930 points

    Hi Brigitte,

    Thank you for your response.
    It is undecided how much capacity will be added.
    Customers want to increase Css capacity as a countermeasure against inrush current.

    They planning to select Css by cut and try.
    However, They would like to know the recommended capacity that TI expects.

    Best regards,
    Brigitte

  • 0 in reply to Tsukui Yusuke
    TI__Guru 61325 points

    Hello Tsukui,

    I would try to stay below 1uF.