Abstract: Circuitry for powering a load and charging of a battery from a power source by a smart power supply is provided. The smart power supply controls the maximum current for battery charging based in part upon variables such as the maximum rate of charge of the battery and maximum source current. The smart power supply is thus capable of providing the power requested by the load, and use the remaining power for battery charging.

Abstract: A power management circuit is arranged to apply power to and remove power from its own oscillator to conserve power. A power-on reset circuit provides a power-on-reset signal to a state machine. The state machine contains states that are programmed with information that is used to power up or down various subsystems within a device that includes the power management systems, including the oscillator of the state machine. The state machine assumes a known state and applies power to the oscillator in response to the power-on-reset signal. The state machine changes states in response to system events (e.g., a keypress). The state machine also maintains power to the oscillator during the period of time and which the state machine requires clock signal from the oscillator. The state machine can power down the oscillator to conserve power when the state machine does not require a clock signal from the oscillator.