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Phase-lock loop startup circuit and voltage controlled oscillator reference generator

  • US 7,764,129 B1
  • Filed: 12/18/2008
  • Issued: 07/27/2010
  • Est. Priority Date: 12/18/2008
  • Status: Active Grant
First Claim
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1. A method of startup for a phase-locked loop (PLL), the method comprising:

  • at initiation of the PLL, providing a reference voltage from a startup voltage source to an input of a voltage controlled oscillator (VCO) in the PLL, wherein the reference voltage is set to a predetermined minimum voltage;

    stepwise increasing the reference voltage from the predetermined minimum voltage;

    comparing a frequency of a reference signal input to the PLL with a frequency of a feedback signal originating from an output of the VCO of the PLL to determine a frequency differential as the reference voltage increases;

    determining whether a convergence criterion is met according to the frequency differential;

    while the convergence criterion is not met, increasing the reference voltage; and

    when the convergence criterion is met, replacing the reference voltage provided by the startup voltage source with an operational voltage generated by an operational voltage source.

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