Patent ID: 7907022

Claim:
A phase-locked loop (PLL) system, comprising: a calibration circuit for generating a calibration current; a voltage-controlled oscillator (VCO), comprising: a voltage-to-current converter for converting a control voltage to a first current; and a current-controlled oscillator connected to the voltage-to-current converter and the calibration circuit, wherein the current-controlled oscillator generates an oscillator signal based on a sum of the first current and the calibration current; a phase detector, coupled to the VCO, for generating an error signal based on an input reference signal and at least one fraction of the oscillator signal; and a charge pump circuit, connected to the phase detector, the voltage-to-current converter and the calibration circuit, for receiving the error signal, wherein the charge pump circuit generates a charge pump current by summing a first fraction of the first current and a second fraction of the calibration current, wherein the charge pump current is used to generate the control voltage based on the error signal.