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LM5069: dV/dt Start-up

Brian Wang0928
Genius 12890 points
Part Number: LM5069

In the application circuit as below red color, there is a dV/dt startup circuitry. Could you guide me when it should be used and how to select the capacitor value for good startup during operation? Is there any calculation formula? Thanks. 

Regards

Brian

  • 0
    TI__Guru** 104466 points

    Hi Brian,

    The dVdt circuit is needed to control inrush current while starting a large capacitive loads. It should be selected based on the target inrush current and Cout value.

    Iinrush = Cout * dVout /dt

    The dVdt capacitor sets the dVout /dt rate as follows

    Igate = Cdv/dt * dVout /dt      ==>        Igate = Cdv/dt * Iinrush / Cout 

    I suggest to use design calculator http://www.ti.com/product/LM5069/toolssoftware to calculate Cdv/dt value.

    Best Regards, Rakesh