Charge Pumps

Summary

Charge pumps are capacitive DC‐DC converters. They are also called voltage multipliers because the output voltage is usually higher than the input voltage. This chapter analyzes the three effects: Step‐wise ramp‐up, voltage droop, and output voltage ripple. It will lead to essential design guidelines for charge pumps. The switches in charge pumps can be implemented using diodes or transistors. While the diodes simplify the design, the charge pump performance suffers from the diode forward drop. The output voltage of charge pumps varies over corners depending on parasitics and the load current. Multiple charge pump stages can be cascaded if the output voltage level is insufficient. Conventional charge pumps utilize hard‐switching charge transfer from one capacitor to another. This results in inrush currents and high current spikes if the voltage difference between capacitors is large. Charge pumps are widely used in gate supply circuits.