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TL4242 PWM SPEC

Kai Hsiao
Guru 12675 points
Other Parts Discussed in Thread: TL4242

Dear Sir 

Below is MIC4802’s Dimming SPEC 200Hz~500KHz ,How about TL4242??

Does TI  have any Duty vs LED current curve ??

Thanks

  • 0
    TI__Expert 3460 points
    Hi Kai,

    I believe I answered this for your counterpart, but I will copy most of the information here.

    TL4242 low end frequency: This can be as low as the engineer desires. The 200Hz is common because at that frequency the device is guaranteed to be switching fast enough to create a dimming effect. If you lower into a frequency like 150Hz, you would see blinking rather than dimming.

    TL4242 high end frequency: A typical device can be PWM as fast at 250kHz. I would caution that the goal shouldn’t just be to increase the PWM frequency. You want to optimize the frequency such that you achieve the lowest average current. An example I showed was how you could use PWM frequency to reduce the current to 1/3 of the steady state current(my test setup reduced the current from 112mA to 42mA!). As you continue to increase the frequency, the output may not pull down fully, and you can get an undesirable effect of increasing the average current from the lowest value.

    Finally, for my example I stuck with a 50% duty cycle. You also have the option to reduce the duty cycle for more substantial current reduction (over 10mA). I hope this information helps!