A disclosed device for generating a pulse-width modulated signal according to image data and based on a pixel clock signal includes a pixel clock generating unit configured to generate the pixel clock signal and a modulated data generating unit configured to generate the pulse-width modulated signal. The pixel clock generating unit includes a multi-phase clock signal generating unit, a comparing unit, a frequency calculation unit, a counting unit, and a pixel clock signal output unit. The modulated data generating unit includes a data converting unit, an edge time calculation unit, and a pulse-width modulated signal output unit.