In a preferred embodiment, a battery charging system in the form of an integrated circuit (IC), incorporated in a consumer electronic device, has a charging controller, a charging current generator, a junction temperature sensor, and a device current monitor. The junction temperature sensor provides to the charging controller a measured junction temperature of the IC. The charging current generator utilizes fractional synthesis, which involves regulating the duty cycles of multiple current sources, to achieve increased current resolution. The charging controller regulates the charging current provided by the charging current generator based on the relation of the measured junction temperature to three or more threshold temperatures. The device current monitor provides to the charging controller information about the current utilization of the consumer electronic device, thus allowing the charging controller to determine the device non-charging current and give priority for available current to user applications running on the consumer electronic device.