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LM73605-Q1: soft start with 3.3nF Css

user4979989
Intellectual 2800 points
Part Number: LM73605-Q1

Hi team,

I would like to know if there is any limitation in soft-start time or capacitance, such as minimum soft-start time/minimum capacitance (Css).

My customer placed 3.3nF, the typical soft-start time is 1.65ms, but the result is quite different. (~4ms with 3.3nF Css)

The result is as below:

Could you help to check? My customer's requirement on soft start time is < 2ms, is it doable?

Thanks.

Regards,

Allen

  • 0
    TI__Expert 4555 points

    Hello Allen,

    VOUT tracking also provides the option of ramping up faster than the internal start-up ramp. The FB voltage always follows the lower potential of the internal voltage ramp and the voltage on the SS/TRK pin. If the tracking ramp is delayed after the internal ramp is completed, VFB follows the tracking ramp even if it is faster than the internal ramp. Faster start-up time may result in large inductor current during start-up. Please refer to page 18 & 19 of the datasheet. Let me know if you have more questions. 

    And please close the thread if you think my response answered your question.

    Best Regards,

    Ankit Gupta

    Application Engineer