A delay-locked-loop (DLL) circuit having a DLL that operates when an external clock signal has a low frequency and a DLL that operates when an external clock signal has a high frequency is disclosed. The DLL circuit includes a first DLL and second DLL. The first DLL adjusts a delay time of an external clock signal to generate a first internal clock signal synchronized with the external clock signal when the external clock signal has a low frequency. The second DLL adjusts the delay time of the external clock signal to generate a second internal clock signal synchronized with the external clock signal when the external clock signal has a high frequency.