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LM3435: About ILEDmin

Junya Kato
Expert 1635 points
Part Number: LM3435

Hello Team,

In equation (14) of the datasheet, L=2.18uH is calculated when ILEDmin=600mA. Under this condition, if the LED current is always less than 600mA by I2C setting, will it operate without problems? Is there a lower limit of ILEDmin used to calculate L in equation (12) of the datasheet?  Is the value of the inductor too large to cause problems?

My customer uses an inductor of 330uH calculated with ILEDmin=50mA.In that case the motion is unstable. Therefore, L is calculated at 600mA similarly to EVM, and the LED current is reduced by I2C setting to investigate whether it can be used.

Best regards,
Kato

  • 0
    TI__Mastermind 25500 points

    Hello Kato,

    I'm sorry for the slow response. I have notified the right person to answer your question but I believe he may be travelling so thank you for your patience. Hopefully  you will get a reply soon.

    Regards,

    Clint

  • 0
    TI__Expert 3920 points
    Hi Kato-san,

    Really sorry for my late reply due to my business travel and schedule!

    The projected on time scheme employed by LM3435 requires the converter running in Continuous Conduction Mode (CCM).

    As the datasheet has listed, it is suggested to have ripple current of at least 300 mA peak-to-peak, meaning that the average LED current should not be lower than 150 mA for the fly-back converter having proper CCM operations. (Refer to P. 18, Inductor Selection section of the datasheet)

    Any current that is less than 150 mA nominal could be obtained by programming through I2C.

    Having an inductor of 330 uH does not help as the flyback converter does not have the required inductor ripple current for proper operations.

    I hope the above helps your customer solving the issues!

    Thank you!