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TPS22917: LED voltage adjusting with TPS22917DBVR

ERAY BAKLACI
Prodigy 20 points
Part Number: TPS22917

Hi,

I want to use TPS22917DBVR power switch IC to control the brigthness of an LED with pwm input. For a specific application, i need to adjsut the LED voltage between 0-3.3V DC with a pwm, so i want to use TPS22917DBVR IC for this aim. Is TPS22917DBVR suitable for this application ? Can you give advise, please?

Thanks.

  • 0
    TI__Mastermind 18370 points

    Hi Eray,

    Is my understanding correct that you are looking to toggle the VIN or ON pin with a PWM signal? What will the shortest high pulse width be?

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Prodigy 20 points

    Hi Patrick,

    Yes i will toggle th ON pin with PWM signal, (for example, if VCC is 3.3V and if the duty cycle is 50%, so the output will be 1.65V). The pwm signal frequency is 2kHz, but i can adjust it.

    Thanks.

  • +1 in reply to ERAY BAKLACI
    TI__Mastermind 18370 points

    Hi Eray,

    Ok, then TPS22917 would work, but it has a rather long Ton time (time from when ON goes high to the output is at 90% of the input), at 120us typical for your application about a quarter of the pulse would be occupied by the rise time. I would recommend a device with a fast Ton time (TPS22910A, 2us Ton time) to ensure that your duty cycle is reflected accurately at the output.

    Also, if you are trying to achieve a steady DC voltage at the output (i.e. 1.65V), you would need a rather large capacitor on the output of the load switch. I know a common way to achieve PWM dimming with LEDs is just by inputting a PWM signal at high frequency and the user's eye will average and perceive the duty cycle as brightness, so you may want to consider the tradeoffs of each method.

    Thanks,

    Patrick