Patent ID: 6054903
Filing Date: 2000-04-25
Classification: H03L

Abstract:
A phase-locked loop fabricated on an integrated circuit, the phase-locked loop comprising:a phase/frequency detector, a charge pump, and a voltage-controlled oscillator (VCO) which are coupled together in series to form a feedback loop, wherein the VCO has first and second frequency control inputs and a VCO output, wherein the first frequency control input is coupled to the charge pump and the VCO output is coupled to the phase/frequency detector, the VCO has a first voltage-to-frequency gain from the first frequency control input to the VCO output and a second voltage-to-frequency gain from the second frequency control input to the VCO output, and the phase/frequency detector comprises a reference input for receiving a reference signal having a reference frequency and a feedback input for receiving a feedback signal from the VCO output having a feedback frequency;an on-chip loop filter coupled between the charge pump and the second frequency control input and having an incrementable time constant; andtime constant control means coupled between the phase/frequency detector and the on-chip loop filter for detecting oscillation of the feedback frequency about the reference frequency, initializing the time constant to a preselected value and then incrementing the time constant as a function of the detected oscillation until the phase-locked loop is stable.