GENERAL DESCRIPTION The ACT3780 is a complete battery-charging and system power management solution for portable hand-held equipment using single-cell Lithiumbased batteries. The ACT3780 incorporates ActiveSemi‘s proprietary ActivePath architecture which automatically selects the best available input supply for the system. The ActivePath architecture performs three important functions： First， the battery is charged while powering with the system， minimizing current draw from the battery while ensuring that sufficient current is available to power the system. Second， if no input supply is available， system power is automatically switched to the battery. And finally， if the system load-requirement exceeds the capability of the input supply， ActivePath automatically supplements the input with the battery to satisfy the system’s power requirements. In addition to ActivePath， the ACT3780 charger features a complete， high-accuracy （±0.5%）， thermally regulated， stand-alone single cell linear Li+ charger with an integrated 12V power MOSFET. The ACT3780 is available in a thermally enhanced 4mm × 4mm Thin-QFN44-20.