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AN-2083 LM3444 A19 Edison Retrofit Evaluation Board

Ruwan Subasinghe
Prodigy 110 points

I'm looking at the A19 Edison evaluation board and it says that it's configured to drive 5-13 series LEDs. What is the forward voltage of these LEDs? Or alternately, what is the maximum LED string forward voltage of this reference design? This information is provided on other evaluation boards, but not this one, unless I'm missing something.

  • 0
    TI__Mastermind 25500 points
    3.5V LEDs were used during testing so the EVM as-is is limited by the 50V output capacitor. The app note states you can use up to 18 LEDs if you change the output capacitor. That is about the practical limit for best operation and circuit size. You can increase it further with the proper output capacitor but at that point the regulator is running in dropout so much of the time (the input voltage is lower than the output wants to be) that the output ripple will increase drastically without a very large output capacitor.
  • 0 in reply to Clinton Jensen
    Prodigy 110 points
    Thanks Clinton for the quick reply. This is exactly what I needed to know.