The charger is basically a step-down DC-DC (buck) converter. It requires the input voltage to be higher than the output voltage with some headroom for normal operations.
- The maximum duty cycle specification is one of the factors determines the maximum output voltage at a fixed input voltage. Users should avoid maximum duty cycle operations in their applications by setting VINDPM and IINDPM thresholds correctly.
- Please refer to Extract maximum power from the supply when charging a battery ( https://www.ti.com/lit/an/slyt569/slyt569.pdf ) for the details.