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Lock detector for phase lock loop

  • US 9,906,358 B1
  • Filed: 08/31/2016
  • Issued: 02/27/2018
  • Est. Priority Date: 08/31/2016
  • Status: Active Grant
First Claim
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1. An apparatus comprising:

  • a voltage-controlled oscillator (VCO) configured to provide a plurality of phases of a local clock signal;

    a phase comparator configured to receive a phase of the local clock signal and a reference clock signal, and configured to detect a phase error between the phase of the local clock signal and the reference clock and to responsively output a phase-error signal;

    a frequency-lock assist (FLA) circuit configured to receive two or more phases of the local clock signal and the reference clock signal, and configured to generate an FLA signal by detecting a number of phases of the two or more phases of the local clock signal having transitions of latched values, the FLA signal indicative of a magnitude of a frequency error between the reference clock signal and the local clock signal; and

    an error accumulator circuit configured to receive the phase-error signal and the FLA signal, and to responsively provide to the VCO a VCO control signal to lock the local clock signal to the reference clock signal.

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