Variable delay circuit for controlling delay time and DLLDelay Locked Loop thereof

摘要

PURPOSE: A delay time control circuit for controlling a delay time of a variable delay circuit and a DLL(Delay Locked Loop) having the same are provided to control the delay time without an additional work after a package is completed. CONSTITUTION: A delay time control circuit includes a phase detector(110), a control portion(120), a fuse portion(130), and a selector(140). The phase detector compares a reference clock signal to a predetermined output clock signal and generates a predetermined code control signal. The control portion generates the first code signal of m bits in response to the first control signal and the code control signal. The fuse portion receives the first code signal and cuts the internal fuses in response to the second control signal if the first code signal is fixed to a predetermined value. In addition, the fuse portion generates the second code signals of m bits corresponding to logical values of the cut fuses. The selector selects one of the first code signal and the second code signal in response to the first control signal and outputs the selected signal in order to control a delay time of a variable delay circuit(150).