A method and apparatus for controlling a voltage generator of a memory device are provided. In one embodiment, a first clock signal and a second clock signal are provided. The voltage generator is selectively enabled in conjunction with the first clock signal when a period of the first clock signal is less than a period of the second clock signal and the voltage generator is selectively enabled in conjunction with the second clock signal when the period of the second clock signal is less than the period of the first clock signal.