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LP5524 / LED current ramp up smoothly

S.Satoshi
Guru 21675 points

Hi,

I received following question from my customer. Your advice will be appreciated.

Requirement

  • My customer wan to ramp up LED current smoothly to turn on LED by gradation.

Question

  • Does LED current ramp up smoothly by adding capacitor on ISET pin to delay ramp up of ISET pin voltage? 

Best Regards,

Sonoki / Japan Disty

  • 0
    Guru 21675 points

    Hi team,

    I'm waiting for your comment. Your kind response will be appreciated.

    Best Regards,

    Sonoki / Japan Disty

  • 0 in reply to S.Satoshi
    TI__Prodigy 250 points

    Hi Sonoki,

    Adding a capacitor in parallel with ISET resistor does not make the LED current ramp up smoothly. LED current depends on the current flowing through the ISET pin. Adding a capacitor actually makes the LED current overshoot heavily until the capacitor is charged.

    Only way to ramp LED current smoothly would be to use PWM sweep to EN_x inputs.

    Best regards,

    Anssi Räisänen

    TI Finland development center