A driver integrated circuit (IC) is arranged to selectively operate in a display mode and a touch-sensing mode when the driver IC is coupled to a touch display panel. When the driver IC operates in the display mode, the driver IC controls a plurality of common voltage lines of the touch display panel to have a common voltage. When the driver IC operates in the touch-sensing mode, the driver IC controls a first source line of the touch display panel which corresponds to a specific common voltage line, or controls a neighboring common voltage line of the specific common voltage line, to have a first signal pattern the same as the first signal pattern on the specific voltage line or to be floating, wherein the specific common voltage line is arranged to detect touch currently.