A voltage generator includes a charge pump circuit including a first charge pump having a plurality of first pumping capacitors, and a second charge pump having a plurality of second pumping capacitors having a capacitance different from a capacitance of each of the plurality of first pumping capacitors. The charge pump circuit is configured to supply a power supply voltage to a power mesh. The voltage generator further includes a controller configured to output a control signal based on a target level of the power supply voltage, and an oscillator configured to output a clock signal to the charge pump circuit. The oscillator outputs the clock signal to one of the first charge pump and the second charge pump based on the control signal.