Abstract: A mobile communication device 100 has a digital subsystem (110) and a radio frequency subsystem (108), and is powered by a battery (102) which is charged via a charge control circuit (106) using an external power supply (104) connected to the mobile communication device in a single path configuration. The mobile communication device permits limited operation of the mobile communication device by a user while the battery voltage is sufficient to power the digital subsystem but not yet sufficient to power the radio frequency subsystem. The delay in operation is minimized, however, because once charging commences, the battery voltage rises sufficiently fast that, typically, by the time the digital subsystem is initialized, enabled, and powered up, the battery voltage will be sufficient to enable the radio frequency subsystem.

Abstract: Supply voltages within a data processing system may be controlled by a voltage control module which can provide digital signals to a power management unit to cause changes in supply voltages without software intervention. For example, in one embodiment, a voltage control signal and a standby signal may be provided to control the supply voltages output by a voltage regulator within the power management unit. In one embodiment having multiple processors, a voltage control signal and a standby signal corresponding to each processor may be provided to the power management unit which has a voltage regulator supplying an independently controlled supply voltage to each processor. Alternatively, a voltage regulator, a voltage control signal, and a standby signal may be shared by multiple processors, where the voltage control module may ensure that the supply voltage is changed only when the change is appropriate for all processors sharing the same voltage regulator.