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BQ25570: VIN_DC capacitance selection

Claire Yang
Prodigy 50 points
Part Number: BQ25570

Hi TI team,

Here's an elaboration of choice of VIN_DC capacitance, and it says if the source impedance is dominated by capacitive behavior, VIN_DC capacitor should scale according to capacitance of output source.

In my application, the power source is high impedance (~MΩ) resulting from low capacitance (~pF). My questions are

1. Should I scale up or scale down the VIN_DC capacitor?

2. Any other points I should pay attention to in order to facilitate power absorbing from a capacitive-dominated power source?

Thank you!

Claire

  • 0
    TI__Genius 13235 points

    Hi Claire,

    The input capacitance is used to regulate the period between charging pulses. When input falls below the configured MPPT threshold charging stops until it has recovered above that voltage. By increasing input capacitance the period between charging pulses can increase and potentially have higher output ripple. The recommended 4.7 uF input capacitor would provide a good starting point but we don't have sufficient data for other C and L values at the input. 

    Best Regards,

    Juan Ospina