The wireless device described herein uses a single crystal oscillator to generate the high and low frequency clock signals required by the wireless device during both active and inactive radio communications. An exemplary multi-mode clock unit comprises a single crystal oscillator operable in a normal power mode and a reduced power mode, and a control unit that selectively switches the crystal oscillator between the first and second power modes based on a current clock signal quality requirement. The control unit may selectively switch between the first and second power modes by selectively varying a capacitive load of the crystal oscillator and/or by varying a drive signal of the crystal oscillator. For example, the control unit may select the normal power mode when a cellular transceiver is active, and a reduced power mode when the cellular transceiver is inactive to reduce power consumption during the inactive state.