The NCP1851 is a fully programmable single cell Lithium-ion switching battery charger optimized for charging from a USB compliant input supply and AC adaptor power source. The device integrates a synchronous PWM controller, power MOSFETs, and the entire charge cycle monitoring including safety features under software supervision. An optional battery FET can be placed between the system and the battery in order to isolate and supply the system. The NCP1851 junction temperature and battery temperature are monitored during charge cycle, and both current and voltage can be modified accordingly through I2C setting. The charger activity and status are reported through a dedicated pin to the system. The input pin is protected against overvoltages.