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TPS92691: TPS92691 Output Current Ripple

Julian Chen
Expert 2550 points
Part Number: TPS92691

Dear E2E member,

Does ESR of output capacitor will affect the current ripple? 

Customer use the same capacitance but different ESR value then find the current ripple are diffrence.

If yes, may I know the formula?

  • 0
    TI__Mastermind 28655 points
    Hello,

    This is more complicated than a formula. The ESR of a capacitor changes with frequency, the ripple current also is not sinusoidal. You would have to get the information from the capacitor vendor to know what the ESR is at the frequencies that are relevant. Also, the LED string is part of the equation unless the ripple is very small. The LED stack resistance is also not constant, it changes with current. It would probably be easier to simulate it. The simulation would be the output current waveform going to a capacitor with ESR and the LED stack. Changing the ESR would show the change in ripple current/voltage.

    A rough calculation can be done but it will be complex math since the capacitor is R and C in series.

    Regards,