- VCO PLL PLL FREQUENCY SYNTHESIZER WITH MULTI-CURVE VCO IMPLEMENTING CLOSED LOOP CURVE SEARCHING USING CHARGE PUMP CURRENT MODULATION

摘要

the present invention is a multi having action curves of a set-curve voltage as the phase locked loop circuit using a controlled oscillator (VCO), each of the operating curve is different from the frequency range spanning the control voltage range corresponding to, it initiates the phase locked loop circuit. A phase locked loop circuit includes a phase and frequency detector and a multi-to drive the charge pump - including a digital control circuit configured to use a closed-loop curve search operation to select one of the operating curve at the curve VCO to generate a curve selection signal and , selected operating curve is used by the VCO to generate an output signal having an output frequency near the same as the target frequency of the phase-locked loop or thereby. In one embodiment, the digital control circuit to increase the charge pump current greatly than the nominal current value for the closed-loop search operation curve and the curve after the operation selected to set the charge pump current to the nominal current value.