Abstract:
In this thesis, the literature relating to charge pump dc-dc converters and
their uses is reviewed. Charge pumps are useful in many circuits, including low-voltage
circuits, dynamic random access memory circuits, switched-capacitor circuits,
EEPROM's and transceivers. The important issues relating to charge pump
design are power efficiency, output voltage ripple and area efficiency.
This thesis describes the operation of three types of charge pump circuits.
Power efficiency theory of charge pumps is discussed in detail. A method of estimating
the output ripple of a charge pump from the size of the capacitors used
is described. The optimal distribution of available capacitance for minimizing output
ripple or maximizing power efficiency is derived. The tradeoffs between output
ripple, power efficiency and total capacitance are discussed. The considerations involved
in the design of charge pump circuits are described. A new charge pump
circuit that uses two cascoded buffer transistors to improve the area efficiency is
proposed. An implementation consisting of one of each of the three types of charge
pumps was simulated for a 0.35-micron CMOS process. The simulation results verify
the improved area efficiency of the double cascode charge pump.
