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Original question:

WEBENCH® Tools: LM3409 FET dimmer

LM3409HV: Maximum design current

Rolf Mogster1
Prodigy 10 points
Part Number: LM3409HV
Other Parts Discussed in Thread: LM3409

I want to design an LED controller using the LM3409HV.  

The LED I plan to drive is rated for 5A.  

Do I design for 4A and set I_LEDpp to 1A to get to 5A, or do I design for 5A with I_LEDpp set to a lower value?

Looking for a best practice here.  Plus I do not want to blow any diodes.

  • 0
    TI__Mastermind 28655 points

    Hello,

    I would look at the design equations in the datasheet.  The LM3409 regulates peak current so if you designed for I_LEDpp at 1 Apkpk then you would set the current sense to 5.5A.  This way you get 5.5A - 1 Apkpk/2 = 5A average.  This is if you want 5A average.  Note this inductor current, if you have output capacitance the LED current ripple will be less.

    If you want lower average current design for lower.

    Best Regards,