A technique to increase the efficiency of high-voltage charge pumps

A charge pump that utilizes a MOSFET body diode as a charge transfer switch is discussed. The body diode is characterized and a body diode model is developed for simulating the charge pump circuit. A 10% increase of voltage gain has been achieved in the proposed switching technique when compared with a traditional Dickson charge pump. The top plate and bottom plate switching technique have also been illustrated to improve the efficiency of the charge pump. A six-stage Dickson charge pump was designed to produce a 19 V output from a 3.3-V supply, using a 4 MHz, two-phase nonoverlapping clock signal driving the charge pump. The design was fabricated in a 0.35-mu m SOI CMOS process. An efficiency of 79% is achieved at a load current of approximately 19 mu A.