| CPC H03L 7/095 (2013.01) [H03L 7/0812 (2013.01); H03L 7/0891 (2013.01); H03L 7/091 (2013.01)] | 20 Claims | 

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               1. A circuit comprising: 
            a phase detector configured to produce a first up signal and a first down signal based on a difference between a reference clock and a feedback clock; 
                a harmonic detector coupled to the phase detector, the harmonic detector configured to produce a second up signal based on the first up signal and whether the harmonic detector detects a harmonic lock between the reference clock and the feedback clock based on a first clock phase and a second clock phase; and 
                a false lock detector coupled to the phase detector and to the harmonic detector, the false lock detector configured to produce a second down signal based on the first down signal and whether the false lock detector detects a false lock between the reference clock and the feedback clock based on a third clock phase and a fourth clock phase. 
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