BQ24157: what's the function of Cap connected in PMID pin of BQ24157 ?

Hi Fandy,

The PMID cap is the input capacitor for the buck dc/dc converter. It is placed after the reverse blocking FET between VBUS and the high side FET of the buck converter.  Placement of this capacitor as close to the IC PMID pin and GND pin is critical for best buck converter performance.