Patent ID: 8400212

Claim:
A charge pump system, comprising: a charge pump circuit, connected to receive a control signal and in response thereto, provide an output voltage at an output node; and regulation circuitry responsive a multi-bit digital value, including: a first comparator, having as output the control signal, a first input connected to receive a first reference voltage, and a second input connected to a first node; a first current branch connected between the output node and ground, comprising: a first variable resistance connected between the output node and the first node, the value of the first variable resistance is determined by a first set of bits of the digital value; a first fixed resistance connected between the first node and ground; a second current branch connected between the output node and ground in parallel with the first current branch, the second current branch comprising: a second variable resistance connected between the output node and ground, including a fixed portion and an adjustable portion having a value determined by a second set of bits of the digital value, the bits of the second set being of lesser significance than the bits of the first set of bits in the digital value; and a unity gain op-amp section, including: a first transistor connected between the output node and the second variable resistance; and a second comparator having an output connected to the control gate of the first transistor, a first input connected to receive a second reference voltage, and a second input connected to a node between the first transistor and the second variable resistance.