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TPS22975: Regarding the Calculation Method for the Output Voltage Rise Slope of TPS22975

Boris liu
Prodigy 20 points
Part Number: TPS22975


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  • 0
    TI__Mastermind 34471 points

    Hi Boris,

    Sorry for the delay.

    1. Table-1 contains the measured values which are obtained on device under test. Equation gives you the approximate value of rise time. For 3.3V/1000pF, it's matching very closely.

    2. CL is not considered as inrush current is controlled by CT cap not the output capacitor.

    3. 10x input cap is in recommendation. However you can put CIN> COUT. 100uF at CIN should be fine.

    Thanks

    Amrit 

  • 0 in reply to Amrit Jit
    Prodigy 20 points

    HI Amrit

    Thank you for your response. Currently, I plan to use CL as 47μF and CIN as 220μF (the maximum current for LCD 3.3V is 280mA). Considering the timing requirement for the LCD power-off (0.2ms to 20ms), I selected a 47μF capacitor, setting the power-off fall time to 0.3ms. The charge Q = 0.28A * 0.0003s = 0.000084C, and C = Q/ΔU = 0.000084C / 3.3V = 25.45μF. However, the internal pull-down resistor of 230Ω in the TPS22975 was not taken into account. Is this design feasible?