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WEBENCH® Tools/LM5165: Efficiency chart differences

Part Number: LM5165

Tool/software: WEBENCH® Design Tools

Hello,

I am interested in the step-down converter LM5165.
That's why I used the Excel Tool "LM5165 Wide Vin Low Iq Buck Converter Quickstart Design Tool.xlsm" and the Online WEBENCH Designer.
But the efficiency charts are quite different (with (nearly) the same parameters and component values).

Why are there such big differences (e.g. Iout = 80mA> 78% and 87%, 10mA> 56% and 85%)?
Am I doing something wrong ?


with best regards

Markus

  • Hi Markus,

    Could you please share the exact conditions for which you are observing these results?

    You can share your design using the "Share Design tab " to this mail id atul_k@ti.com

    Thanks and Regards,

    Atul.

  • Hi Markus,

    Given the output power is so low and the various component dependencies (core loss, effective output cap, etc.), we recommend you to perform an experimental measurement to validate the achievable efficiency.

    Since the switching frequency is higher in this design (350kHz) – this shortens the PWM on-time and thus the energy per pulse delivered to the load, leading to lower efficiency. In general, lower L and higher Cout will increase light-load efficiency.

    Thanks and Regards,
    Atul