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LM25037: How can I determine the required soft-start time?

Istvan Adam
Prodigy 90 points
Part Number: LM25037

Tool/software:

Hi,

I’m designing a 12 V to 360 V push-pull converter with an LM25037. The maximum output current is 1.2 A. The output inductance is 3.6 mH and the output capacitance is 68 µF.
My question is: how can I determine the soft-start time I need?

  • +1
    TI__Guru 73725 points

    Hi,

    The soft start time is to reduce power on surge current. You need to find how much surge / inrush current at input is allowed to help to calculate the soft time. The other factor is do you have power on time requirement, for example, the Vout needs to reach 90% of its regulation in 10ms, or 50ms, or what? This is another way to help calculate the soft start time.

    After you find these, you can calculate the soft start time capacitor value for initial use - then you can bench tune up. Or if you want, you can use simulation to make tune up for your design before the bench work.