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LM3424: LM3424

Chris Blanc
Prodigy 20 points
Part Number: LM3424

Hi,

I am using the AN-1969 LM3424 Boost Evaluation Board.

I would like to use it with a constant current of 500 mA and 18 leds in series.

When I do, it does not work and I don't see which component I should change to increase the Vout

Thanks for your help

Chris

  • 0
    TI__Mastermind 28655 points

    Hello Chris,

    So you're probably tripping OVP.  To raise that to approximately 65V change R11 to 9.76K, if you use a 10K it'll be a little lower (you can calculate that from the datasheet or EVM report.  Also, R9 will have to double from 0.1 ohm to 0.2 ohm to get 500 mA.  The output capacitors are rated for 50 volts 18 LEDs at 3V  will be 54V (I'm not sure which LEDs you are using) but you may want to change them.  You may have to look at the slope compensation depending on what input voltage you will be running at (lowest is the worst case).

    Regards,