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WEBENCH® Tools/LM3409HV: LM3409HV different result from calculation & Webench

Yon Chet Chen
Prodigy 20 points
Part Number: LM3409HV
Other Parts Discussed in Thread: LM3409,

Tool/software: WEBENCH® Design Tools

Good Day,

I am doing a deign as following.

Input Voltage = 48V

Led Voltage = 3.3V

LED Current = 3.0A

LED in series = 10cs

When do own calculation, I found out the Inductor is 22uH, and hen i tried to use webench to simulate, the inductor value has become 180uH.

And Seem like WEBENCH not allow us to select the switching frequency to 525kHz. And only allowed to selected up to 149kHz.

Thanks.

YC

  • 0
    TI__Mastermind 25500 points

    Hello,

    That seems a bit odd about the webench, but sometimes there are odd things in webench I don't understand. They may just have a setting to limit the switching frequency at higher input voltages and power levels for thermal reasons and that results in a higher inductor value.

    In any case you should go with your calculations. It will likely need some adjusting on the bench either way and the LM3409 is a very robust and easy to use device. It doesn't have any stability issues to worry about like a current mode control device would.

    Regards,

    Clint

  • 0 in reply to Clinton Jensen
    Prodigy 20 points

    Good Day,

    Thanks for the reply. In fact even I use back the value shown inside the LM3409HV datasheet, the webbench given a totally different result from the value inside the datasheet. I think this is all related to the input voltage range.

    Cheers !

    YC