A data driver according to an exemplary embodiment includes a plurality of first output channels, a plurality of second output channels, a data controller and a data driving integrated circuit IC. The plurality of first output channels are connected to a plurality of data lines. The data controller receives an image data signal and a data control signal. The data controller generates an image data of one frame unit according to the image data signal and the data control signal. The data controller generates an output channel on/off data based on channel selection data. The data driving IC generates a plurality of data signals and a plurality of dummy signals according to the image data of one frame unit. The data driving IC switches a plurality of first switches transmitting the plurality of data signals to the plurality of first output channels and a plurality of second switches transmitting the plurality of dummy signals to the plurality of second output channels. The image data signal includes the channel selection data, the plurality of first output channels and the plurality of second output channels.