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Phase-locked loop for stably adjusting frequency-band of voltage-controlled oscillator and phase locking method

  • US 7,471,159 B2
  • Filed: 11/13/2006
  • Issued: 12/30/2008
  • Est. Priority Date: 11/25/2005
  • Status: Active Grant
First Claim
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1. A phase-locked loop comprising:

  • a basic phase-locked loop circuit comprising a voltage-controlled oscillator (VCO), the basic phase-locked loop circuit generating an output clock signal which is phase-locked with an input clock signal using the VCO which oscillates in response to an oscillation control signal and changes an oscillation frequency band depending on a frequency band selection digital value; and

    a frequency band controller which generates the frequency band selection digital value in response to the input clock signal and the oscillation control signal,wherein the frequency band controller comprises;

    a comparator which compares the oscillation control signal with a first reference voltage to generate an up-count signal, and compares the oscillation control signal with a second reference voltage to generate a down-count signal;

    a stabilization controller which generates an enable signal to update an operating frequency region of the VCO in response to the input clock signal and the oscillation control signal; and

    a counter which receives the up-count signal and the down-count signal from the comparator, selectively outputs the up-count signal in response to the enable signal so as to increment the frequency band selection digital value, and selectively outputs the down-count signal in response to the enable signal so as to decrement the frequency band selection digital value.

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