Patent ID: 8860480

Claim:
A charge pump comprising: a capacitor coupled to an output node; a first input to connect to a first power supply; a second input to connect to a second power supply having a voltage lower than the first power supply; a first bias input to connect to a first bias voltage; a second bias input to connect to a second bias voltage, wherein the first bias voltage is positive relative to the output node, and wherein the second bias voltage is negative relative to the output node; a pump up current path defined by: a first transistor connected between the first input and a first intermediate node and comprising a first gate to connect to a first output of a phase detector, and a second transistor directly connected between the first intermediate node and the capacitor and comprising a second gate connected to the first bias input; a pump down current path defined by: a third transistor connected between the second input and a second intermediate node and comprising a third gate to connect to a second output of the phase detector, and a fourth transistor connected between the second intermediate node and the capacitor and comprising a fourth gate connected to the second bias input; a first alternate current path between the first intermediate node and the second input and configured to conduct current for a brief period of time when the first transistor is switched to an off state; and a second alternate current path between the second intermediate node and the first input and configured to conduct current for a brief period of time when the third transistor is switched to an off state.