Patent ID: 8222937

Claim:
A charge pump comprising: pull-up circuitry configured to generate pull-up current to increase voltage at a charge pump output, the pull-up circuitry comprising a current source and a controlled transistor having a gate adapted for connection to a first input signal for being controlled thereby, the pull-up circuitry connected between a positive voltage supply and a charge pump output node; pull-down circuitry configured to generate pull-down current to decrease voltage at the charge pump output, the pull-down circuitry comprising a current source and a controlled transistor having a gate adapted for connection to a second input signal for being controlled thereby, the pull-down circuitry connected between a ground voltage supply and the charge pump output node, and the first and second input signals being derived from up and down signals, respectively; an operation amplifier having two inputs and an output, the operational amplifier configured to reduce phase error, one of the inputs of the operational amplifier connected to the charge pump output node; and a reference current source having a plurality of select transistors and a plurality of mirror master transistors, the mirror master transistors coupled to slave transistors of either the pull-up circuitry or the pull-down circuitry to mirror variable current in the slave transistors.