A semiconductor integrated circuit includes a DLL controlling block configured to enable or disable an update enable signal by detecting a change in a voltage level of a phase detecting signal during a predetermined time when an operation enable signal and a threshold phase difference detecting signal are enabled, and a delay locked loop (DLL) circuit configured to generate an output clock signal by delaying and driving the reference clock signal and to control a frequency of a change in the delay amount of the reference clock signal in response to the update enable signal.