Ahmed Emira, et al., "50V All-PMOS Charge Pumps Using Low-Voltage Capacitors" IEEE Transactions on Industrial Electronics 60, (10), 2013, 4683.
Abstract: In this paper, two high-voltage charge pumps (CPs) are introduced. In order to minimize the area of the pumping capacitors, which dominates the overall area of the CP, high-density capacitors have been utilized. Nonetheless, these high-density capacitors suffer from low breakdown voltage, which is not compatible with the targeted high-voltage application. To circumvent the breakdown limitation, a special clocking scheme is used to limit the maximum voltage across any pumping capacitor. The two CP circuits were fabricated in a 0.6- μm CMOS technology with poly0-poly1 capacitors. The output voltage of the two CPs reached 42.8 and 51 V, whereas the voltage across any capacitor did not exceed the value of the input voltage. Compared with other designs reported in the literature, the proposed CP provides the highest output voltage, which makes it more suitable for tuning MEMS devices.