Innovation of Switched-Capacitor Voltage Multiplier: Part 2: Fundamentals of the Charge Pump

Abstract

In Part 1 of this series [1], a brief history of switched-capacitor voltage multiplier was reviewed starting with Greinacher's voltage doubler in 1914 [2]. It was concluded that the Falke-Dickson [3], [4] parallel voltage multiplier or charge pump was best for integrated circuits where capacitors and switching devices had significant parasitic capacitance [5]. In this Part 2, the structure of integrated switching devices and capacitors is reviewed. An equivalent circuit and power efficiency of the charge pump is discussed in both the ideal and real cases in terms of threshold voltage of switching transistor and parasitic capacitance. Finally, several design optimizations are described.