| 摘要 |
<p>Disclosed is a phase-locked loop (PLL) circuit using a multi-curve voltage-controlled oscillator (VCO) having a plurality of operating curves, each operating curve corresponding to a different frequency range over a control voltage range. The PLL circuit includes a digital control circuit generating a curve selection signal using a closed loop curve search operation to select one of the operating curves in the multi-curve VCO, and the selected operating curve being used by the VCO generates an output signal with an output frequency being equal or close to a target frequency of the PLL. According to an embodiment, the digital control circuit implements a binary jump method, and an operating curve is selected when the operating curve has an output frequency meeting the target frequency with the control voltage being within a first voltage range that is a narrow central voltage range within the control voltage range.</p> |
