According to an example embodiment, a display driving integrated circuit (IC) includes a timing controller and a plurality of source drivers. The timing controller is configured to output a plurality of signals to the plurality of source drivers, and at least one of the timing controller and the plurality of source drivers operates in a power down mode in at least one of an initializing period, a data transmission period, and a vertical blank period. According to an example embodiment, a mode conversion method used in a display driving IC includes switching between a normal mode to a power down mode in response to a standby control signal. The power down mode is implemented on at least one of a timing controller and a plurality of source drivers included in the display driving IC in at least one of an initializing period, a data transmission period, and a vertical blank period.