Example embodiments include display driver systems having a host with an external image signal receiving unit configured to receive an external image signal and a graphic control unit configured to transmit input control signals. The systems further include a display driver integrated circuit configured to receive the input control signals, generate a screen display sync signal by using a main clock signal when the external image signal includes a moving image, and generate a screen display sync signal by using an internal clock signal when the external image signal includes a still image, the display driver integrated circuit including. Such circuits have a display driver integrated circuit control unit configured to generate a data control signal, a gradation voltage generating unit configured to generate a gradation voltage and transmit the gradation voltage, and a data driver configured to receive the gradation voltage from the gradation voltage generating unit and apply the gradation voltage to data display signal lines of an LCD panel.