Patent ID: 7880517

Claim:
A DLL with power-saving function, the DLL comprising: a VCDL, comprising: a first input end for receiving a first clock signal; a second input end for receiving a controlling voltage; and an output end for outputting a second clock signal by delaying the first clock signal, according to the controlling voltage; and a voltage controlling module coupled to the second input end of the VCDL, the voltage controlling module comprising: a capacitor coupled between the second input end of the VCDL and a ground end, for sustaining the controlling voltage; a phase detector for generating a first controlling signal and a second controlling signal, according to phase difference between the first clock signal and the second clock signal; and a voltage controller, comprising: a current controller, comprising: a first controlling end, for receiving the first controlling signal; a second controlling end, for receiving the second controlling signal; a third controlling end, for receiving a turn-off signal; a first output end for outputting a current controlling signal according to the first controlling signal and the second controlling signal; and a second output end for outputting a boot signal; wherein when the current controller receives the turn-off signal, the current controller outputs the boot signal when a period difference between the first controlling signal and the second controlling signal is larger than a predetermined value to enable the charge pump; and the current controller stops outputting the boot signal when the period difference between the first controlling signal and the second controlling signal is smaller than the predetermined value to disable the charge pump; a charge pump, comprising: a first controlling end coupled to the first output end of the current controller, for receiving the current controlling signal; a second controlling end coupled to the second output end of the current controller for receiving the boot signal; and an output end coupled to the capacitor; wherein when the charge pump receives the boot signal, the charge pump sources or sinks a current with a predetermined magnitude, according to the current controlling signal.