3. Design of DC-DC Dickson Charge Pump

This chapter expands upon circuit theory of DC-DC Dickson charge pump and discusses how the charge pump voltage multiplier is optimally designed. Design equations and equivalent circuit models are derived for the charge pump. Power efficiency of the charge pump is described as a function of device and design parameters. Using the model, optimizations are discussed to minimize the circuit area under various conditions that the output current, the ramp time, and the power dissipation are given theoretically. Guideline for comprehensive optimum design is also described.

This chapter is composed of the following. Section 3.1 describes a dynamic behavior of charge pump and the equivalent circuit under the condition that the operation frequency is low enough. Section 3.2 expands upon circuit equations at a moderate to high operation frequency where the switching device is a diode, MOSFET in saturation region, and MOSFET in triode region, respectively. Section 3.3 shows how power efficiency of charge pumps is determined taking the dependence of the output voltage, the threshold voltage of switching device, and parasitic capacitance into consideration. Section 3.4 discusses several optimizations of the circuit with respect to circuit area, rise time, and power, as well as guideline for comprehensive optimum design. Section 3.5 summarizes key design equations.