Patent ID: 7142039

Claim:
A charge pump comprising: a resistor divider connected between an output voltage node and ground; a comparator inputting a reference voltage at one input, and a divided voltage from the resistor divider at another input; a digital control circuit enabled by the comparator, the digital control circuit comprising: a first shift register and a second shift register; a first plurality of parallel transistors and a second plurality of parallel transistors in series between an input voltage node and the ground, each of the first and second plurality of transistors is controlled by the digital control circuit; and a pump capacitor connected to the output voltage node and between the first and second plurality of parallel transistors, the pump capacitor is charged by the first and second plurality of transistors being switched on and off using the first and second shift registers, respectively, wherein gates of the first and second plurality of transistors are coupled to corresponding outputs of the first and second shift register, respectively.