A charge pump includes a first capacitor, a first switch with adjustable on-state resistance, a second switch, a third switch, a fourth switch, a feedback loop, and an oscillator. The first switch is coupled between a first electrode of the first capacitor and an output node. The second switch is coupled between a second electrode of the capacitor and ground. The third switch is coupled between an input node and the second electrode of the capacitor. The fourth switch with adjustable on-state resistance is coupled between the input node and the first electrode of the capacitor. The feedback loop monitors a regulated voltage of the output node and generates a control signal to regulate resistances of the first, fourth switches. The oscillator generates a first and second pulse signals to switch the open and close states of the first, third switches and the second, fourth switches, respectively.