Lock detector for phase lock loop
First Claim
1. A method comprising:
- obtaining a plurality of phases of a local clock signal from a voltage-controlled oscillator (VCO) comprising a plurality of sequentially-connected logic elements, each phase obtained via an output of a respective logic element;
generating a frequency-lock assist (FLA) signal by detecting transitions in each phase of the plurality of phases of the local clock signal in adjacent sampling instants determined by a reference clock signal, the FLA signal indicative of a magnitude of a frequency error between the local clock signal and the reference clock signal; and
applying the FLA signal to an error accumulation circuit, the error accumulation circuit generating a VCO control signal for setting the VCO in a frequency-locked condition based at least on the FLA signal.
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Accused Products
Abstract
Methods and systems are described for generating, using a voltage-controlled oscillator (VCO), a plurality of phases of a local clock signal, generating a phase-error signal using a phase comparator receive a phase of the local clock signal and a reference clock signal, and configured to output the phase-error signal, generating a frequency-lock assist (FLA) signal using a FLA circuit receiving one or more phases of the local clock signal and the reference clock signal, the FLA signal indicative of a magnitude of a frequency error between the reference clock signal and the local clock signal, and generating a VCO control signal using an error accumulator circuit receiving the phase-error signal and the FLA signal, and responsively providing the VCO control signal to the VCO to lock the local clock signal to the reference clock signal.
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Citations
20 Claims
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1. A method comprising:
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obtaining a plurality of phases of a local clock signal from a voltage-controlled oscillator (VCO) comprising a plurality of sequentially-connected logic elements, each phase obtained via an output of a respective logic element; generating a frequency-lock assist (FLA) signal by detecting transitions in each phase of the plurality of phases of the local clock signal in adjacent sampling instants determined by a reference clock signal, the FLA signal indicative of a magnitude of a frequency error between the local clock signal and the reference clock signal; and applying the FLA signal to an error accumulation circuit, the error accumulation circuit generating a VCO control signal for setting the VCO in a frequency-locked condition based at least on the FLA signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus comprising:
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a voltage-controlled oscillator (VCO) comprising a plurality of sequentially-connected logic elements, the VCO configured to provide a plurality of phases of a local clock signal, each phase provided via an output of a respective logic element of the plurality of sequentially-connected logic elements; a frequency-lock assist (FLA) circuit configured to generate an FLA signal by detecting transitions in each phase of the plurality of phases of the local clock signal in adjacent sampling instants determined by a reference clock signal, the FLA signal indicative of a magnitude of a frequency error between the local clock signal and the reference clock signal; and an error accumulation circuit configured to receive the FLA, the error accumulation circuit configured to generate a VCO control signal to set the VCO in a frequency-locked condition based at least on the received FLA signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification