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LM5069: Only required when using dv/dt start-up on the datasheet

Hirotaka Matsumoto
Guru 27525 points
Part Number: LM5069

Hi all

Would you mind if we ask LM5069?

<Question1>
There is the description "only required when using dv/dt start-up" on the datasheet P1.
Do you have any document to design it?
Especially, about R=1kohm, could you let us know how to calculate? 

<Question2>
In relation to <Question1>, what is Q1(PNP transistor) used for?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Expert 5940 points

    Hirotaka,

    1) The design calculator tool will help you with the Ccv_dt capacitor selection.  The 1k, D2 , Q2 part numbers are also listed in the BoM summary of the calculator tool.  The 1k is for base bias.  You should stay with 1k in your design.

    2) The pnp (Q2) is a fast discharge for Cdv_dt when the GATE pin goes low and keeps the high current off the internal pull down FET avoiding any damage that might otherwise occur.

    Brian