| 主权项 |
1. A phase lock loop having a lock detector, comprising:
a phase frequency detector, arranged for generating a first control signal and a second control signal according to a phase difference based on a reference signal and an output signal; a first charge pump, coupled to the phase frequency detector, arranged for providing a first output according to the phase difference; a loop filter, coupled to the first charge pump, arranged for generating a filtered signal according to the first output of the first charge pump; and an oscillator, coupled to the loop filter, arranged for generating the output signal according to the filtered signal; and a lock detector, comprising:
a second charge pump, arranged for providing a second output according to the phase difference;a filter, coupled to the second charge pump, arranged for filtering the second output of the second charge pump to generate a filtered output voltage; anda comparing circuit, coupled to the filter, arranged for comparing the filtered output voltage with a threshold setting to generate a lock indication signal to indicate whether the phase lock loop is in a lock condition,wherein the threshold setting comprises a first threshold and a second threshold, and the comparing circuit is a window comparator arranged for comparing the filtered output voltage with the first threshold and the second threshold and the lock indication signal changes to indicate that the output signal is locked to the reference signal whenever the filtered output voltage enters a region between the first threshold and the second threshold and changes to indicate that the output signal is not locked to the reference signal whenever the filtered output voltage exits the region between the first threshold and the second threshold. |
