Apparatus for supplying clock and method thereof

An apparatus for providing clock and a method thereof are provided. The provided apparatus includes a frequency generation unit and a control unit. The frequency generation unit decides amplitude of a clock signal to be a first amplitude or a second amplitude in response to a mode signal. The frequency generation unit converts an external oscillation signal into the clock signal. The control unit receives the clock signal, and outputs the mode signal in response to a system status signal. The control unit outputs the clock signal to external when determining that the clock signal has a stable oscillation. When the system status signal is a power on signal, the first amplitude is used as the amplitude of the clock signal, and when the system status signal is a power off signal, the second amplitude smaller than the first amplitude is used as the amplitude of the clock signal.