Mobile communication device and integrated circuit thereof

An integrated circuit, adopted by a mobile communication device communicating with a fourth generation (4G) network and a second network, comprising:

• a transceiver, when exchanging an ongoing data transmission with the packet switched network, configured to transmit a first message to the packet switched network, which indicates the mobile communication device will be tuned away from the packet switched network, and perform a subsequent procedure for the second network;
• a first Phase-locked Loop (PLL) circuit, configured to provide a first clock to the transceiver;
• and
• a controller, configured to receive first and second received signals from the transceiver and transmit a first transmitted signal to the transceiver, and when the ongoing data transmission with the packet switched network is not completed, configured to control the first PLL circuit to switch the first clock from a first clock frequency to a second clock frequency after the transceiver transmits the first indication message;
• wherein the ongoing data transmission is suspended and the subsequent procedure is performed after the transceiver transmits the first indication message.