A backlight driving circuit for a display apparatus includes a receiver, a signal modulation detector and a driver. The receiver receives a clock signal and a brightness data signal by a serial transmission and in response to an enable signal. The brightness data signal is synchronized with the clock signal and includes brightness information. The signal modulation detector detects a modulation of the brightness data signal, based on at least one of the clock signal and the enable signal, and outputs a control signal based on a detected result thereof. The driver receives the brightness data signal, in synchronization with the clock signal, selects one of the brightness data signal and a predetermined reference brightness data signal in response to the control signal, generates a driving voltage using the selected brightness data signal, and provides the driving voltage to the backlight unit to control the brightness of the backlight unit.