A display driver generates a respective charge pumping signal and respective driving signals synchronized to a respective same clock signal for each of the CPU and video interface modes. Because such respective signals are synchronized to a respective same clock signal, the noise superimposed on the driving signals applied on a display panel is regular and uniform across the whole display panel, for each of the CPU and video interface modes. Accordingly, affects of such regular noise are advantageously not noticeable to the human eye, for both the video and CPU interface modes of operation.