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LM3509 light load Question

Masazumi Ishii
Genius 3945 points
Other Parts Discussed in Thread: LM3509

Hello.

There is a Light mode and a frequency changes to LM3509.
How many is the current value with which a frequency changes?
Is there an arithmetic expression which takes a frequency out of the load electric current?
the　load electric current　vs　Sw　 frequency　　　　　　　
Is there a chart ?

  • 0
    TI__Intellectual 1040 points
    The light load mode is determined by the inductor current in the power switch, so it is not easily translated to a specific load current since the output referred threshold depends on VOUT, VIN, IOUT. Typically the light load mode will start around 1mA (total output current). Once light load is entered, the light load switching frequency will decrease with falling load current. Above the light load threshold the switching frequency is constant at 1.27MHz.

    Thanks
    Travis
  • 0 in reply to Travis Eichhorn
    Genius 3945 points

    Hello.

    Thank you very much for your answer.

    Question
    ①At 1mA, I enter low load mode.
    When output of a pressure boost converter will be 1mA, this will be low load mode.
    Is this understanding OK?

    ②light load mode：How many is lowest frequency?

    ③Separate sheet.

    Thank you.

    LM3509.pdf