Abstract: A voltage control circuit that utilizes a level-shifter circuit and a switch circuit to isolate a charge pump output terminal from a system voltage source when a charge pump is enabled, and to couple the charge pump output terminal to the system voltage source when the charge pump is disabled. The level-shifter circuit receives the charge pump output voltage as its high voltage supply and the charge pump enable signal as its input signal, and transmits the charge pump output voltage from its output terminal when the charge pump is enabled, and zero volts when the charge pump is disabled. The switch circuit includes a PMOS transistor constructed such that its bulk and source are connected to the charge pump output terminal, and its drain is connected to the system voltage source. The switch circuit also includes a guard ring structure surrounding the PMOS transistor.