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TLC59731: current regulation

Ricardo Medina1
Prodigy 10 points
Other Parts Discussed in Thread: TLC59731, TLC5973

Dear Sir/Madam

I am writing to ask for more information about TLC59731 because I have some doubts about current regulation.

Led driver provides grayscale function with PWM control through serial interface. Then we can select typical sink current value of each channel by external resistor. With temperature Vf of the leds will change, and I would like to know if TLC59731 can hold the current value or current will change as well.

Could you send more information about this?

Best wishes,

  • 0
    TI__Intellectual 955 points

    Dear Medina,

    TLC59731 output is not contrant current driver. So as you wrote, LED current is depend on LED Vf variation mainly.

    LED current can be calcurated by the following shown on page 12 of TLC59731 datasheet.

    IOUTn (mA) = VLED(V) - VF_TOTAL(V) - VOUTn(V) / RLn(ohm)

    If VLED=5.0V, VF=3.2V (@20mA and +25C), 3.0V (@20mA and+85C), 3.5V (@20mA and -20C) and VOUTn=0.29V (@20mA and +25C), 0.31V (@20mA and+85C), 0.27V (@20mA and -20C) and RLn=75ohm, then LED current (IOUTn) is about 20.1mA (@+25C), 22.5mA(@+85C), 16.4mA(@-20C). 

    If you need smaller current deviation, TLC5973 would be better.

    Best regards,

    Kazuya Nakai.