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Phase-locked loop start up circuit

  • US 9,112,507 B2
  • Filed: 03/09/2010
  • Issued: 08/18/2015
  • Est. Priority Date: 03/09/2010
  • Status: Active Grant
First Claim
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1. A phase-locked loop (PLL) circuit, comprising:

  • a voltage-controlled oscillator (VCO) having a VCO input for receiving a control voltage and a VCO output;

    a feedback loop between the VCO input and the VCO output; and

    a start-up circuit having a start-up circuit input and a start-up circuit output, wherein the start-up circuit output is coupled to the VCO input and wherein the start-up circuit input is coupled to the VCO output,wherein the start-up circuit provides a voltage at its start-up circuit output during a start-up phase, which terminates after a predetermined number of feedback pulses are detected by the start-up circuit.

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