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LM3409: 250:1 dimming limited by what?

Brian Angiel
Expert 4090 points
Part Number: LM3409

Hi team,

I am using the LM3409 in a number of designs. This device has a listed dimming range of 250:1. If I am using the Iadj pin to raise and lower current on an LED string, what limits the range to 250:1? Is the internal of the Iadj a complete analog circuit or is there some type of digital conversion going on with discrete steps?

Thanks,

Brian Angiel

  • 0
    TI__Mastermind 28655 points
    Hello Brian,

    It is not limited however there is a limit how low it can go because of the minimum on-time. After on off-time cycle the minimum on-time must happen. Also, accuracy drops as the dim ratio grows. There is no digital conversion in the part for dimming.

    Best Regards,