Method and apparatus for operating a mobile communication device coupled with an external power supply for charging a battery of the mobile communication device

A method of operating a mobile communication device while charging a battery of the mobile communication device, the battery having a battery voltage, comprising:

• connecting an external power source to the mobile communication device;
• charging the battery from the external power;
• while the battery voltage is below a first level, maintaining a digital subsystem and a radio frequency subsystem of the mobile communication device in an unenabled state;
• while the battery voltage is above the first level and below a second level, enabling the digital subsystem and maintaining the radio frequency subsystem in the unenabled state while charging the battery of the mobile communication device;
• and
• while the battery voltage is above the second level enabling both the digital and radio frequency subsystems while charging the battery of the mobile communication device;
• wherein the digital and radio frequency subsystems are both powered by the battery voltage.

A method of operating a mobile communication device having a battery, the battery having a battery voltage, an external power supply initially coupled to the mobile communication device for charging the battery, the method comprising:

• disconnecting the external power source from the mobile communication device;
• if the battery voltage is above an upper level, maintaining both a digital subsystem in a powered up state and a radio frequency subsystem in a powered up state;
• if the battery voltage falls below the upper level, maintaining the digital subsystem in the powered up state and disabling the radio frequency subsystem;
• if the battery voltage falls below a lower level, disabling both the digital subsystem and radio frequency subsystem;
• while the battery voltage is above upper level, applying an upper regulated voltage to an oscillator providing a clock signal to the digital and radio frequency subsystems;
• and
• while the battery voltage is below the upper level, applying a lower regulated voltage to the oscillator.