Patent ID: 7557641

Claim:
A charge pump comprising: a first input terminal configured to receive a first supply voltage; a second input terminal configured to receive a second supply voltage; an output terminal configured to provide an output voltage; a first capacitor; a second capacitor; and interconnection circuitry for wiring at least one of the first capacitor and the second capacitor to the input terminal in a first configuration which implements a first operational phase, a second configuration which implements a second operational phase, and a third configuration which implements a third operational phase, wherein the output voltage is less than the first supply voltage during the first, second and third operational phases, and wherein during the first operational phase, the first and second capacitors are coupled in series between the input terminal and the second input terminal, such that the first capacitor is charged to a first capacitor voltage and the second capacitor is charged to a second capacitor voltage, wherein during the second operational phase, the first capacitor is coupled between the first input terminal and the output terminal, such that the output voltage is equal to the first supply voltage minus the first capacitor voltage, and wherein during the third operational phase, the first and second capacitors are coupled in series between the input terminal and the output terminal, such that the output voltage is equal to the first supply voltage plus the first capacitor voltage minus the second capacitor voltage.