Patent ID: 7768150

Claim:
A power management unit for a battery-operated electronic device having a bus interface for the interconnection with another electronic device, the power management unit comprising: an electric energy storage element coupled between a battery of the battery-operated electronic device and a voltage supply line of the bus interface, the electric energy storage element being operable to charge/discharge electric energy; a drive circuitry arranged to control a charge/discharge of the electric energy storage element, wherein the drive circuitry is operable to: cause an electric power supplied by said another electronic device through the voltage supply line to re-charge the battery, as being reduced in voltage from a nominal voltage of about 5.0 volts to a nominal voltage of about 3.6 volts by a DC-DC voltage step-down converter having an inductor; or in case said another electronic device does not supply electric power, cause the battery to supply electric power to said another electronic device through said voltage supply line, as being increased in voltage from a nominal voltage of about 3.6 volts to a nominal voltage of about 5.0 volts by a DC-DC voltage step-up converter that utilizes the inductor of the DC-DC voltage step-down converter.