AUTOMATIC DETECTION OF CHANGE IN PLL LOCKING TREND
First Claim
1. A phase lock loop (PLL), comprising:
- a phase frequency detector (PFD) configured to compare a first frequency of a first time-varying signal and a second frequency of a second time-varying signal to provide a frequency error component of an error signal in a first mode of operation and in a second mode of operation;
a time-to-digital converter (TDC) configured to compare a first phase of the first time-varying signal and a second phase of the second time-varying signal to provide a phase error component of the error signal in the second mode of operation;
a digital controlled oscillator (DCO) configured to adjust the second frequency and the second phase based upon the error signal; and
a controller configured to;
compare a trend of the error signal to a previous trend of the error signal to detect for a change in the trend of the error signal, andinitiate a change in a mode of operation of the PLL from the first mode of operation to the second mode of operation or from the second mode of operation to the first mode of operation upon detecting the change in the trend of the error signal.
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Accused Products
Abstract
A phase lock loop (PLL), such as an all digital phase lock loop (ADPLL) to provide an example, of the present disclosure operates in a frequency tracking mode to adjust a frequency of the output signal to be proportional to a frequency of a reference input signal, or, in a phase tracking mode to adjust a phase of the output signal to match any variations in the reference input signal. The ADPLL includes a phase and/or frequency detector that provides an error signal representing a difference, in frequency and/or phase, between the output signal and the reference input signal. The ADPLL monitors a trend of the error signal, such as a positive trend, a negative trend, or a flat trend to provide some examples, and switches among the frequency tracking mode and the phase tracking mode upon detecting a change in the trend of the error signal.
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Citations
20 Claims
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1. A phase lock loop (PLL), comprising:
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a phase frequency detector (PFD) configured to compare a first frequency of a first time-varying signal and a second frequency of a second time-varying signal to provide a frequency error component of an error signal in a first mode of operation and in a second mode of operation; a time-to-digital converter (TDC) configured to compare a first phase of the first time-varying signal and a second phase of the second time-varying signal to provide a phase error component of the error signal in the second mode of operation; a digital controlled oscillator (DCO) configured to adjust the second frequency and the second phase based upon the error signal; and a controller configured to; compare a trend of the error signal to a previous trend of the error signal to detect for a change in the trend of the error signal, and initiate a change in a mode of operation of the PLL from the first mode of operation to the second mode of operation or from the second mode of operation to the first mode of operation upon detecting the change in the trend of the error signal. - View Dependent Claims (2, 3, 4, 5)
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6. A method for operating phase lock loop (PLL), the method comprising:
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comparing, in a first mode of operation, a first frequency of a first time-varying signal and a second frequency of a second time-varying signal to provide a frequency error component of an error signal; comparing, in a second mode of operation, the first frequency of the first time-varying signal and the second frequency of the second time-varying signal to provide the frequency error component of the error signal and a first phase of the first time-varying signal and a second phase of the second time-varying signal to provide a phase error component of the error signal in the second mode of operation; adjusting the second frequency and the second phase based upon the error signal; comparing a trend of an error signal to a previous trend of the error signal to detect for a change in the trend of the error signal; and initiating a change in a mode of operation of the PLL from the first mode of operation to the second mode of operation or from the second mode of operation to the first mode of operation upon detecting the change in the trend of the error signal. - View Dependent Claims (7, 8, 9, 10)
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11. A controller for controlling a phase lock loop (PLL), the controller comprising:
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means for generating a clock signal based on an error signal, the error signal representing a difference between a frequency or a phase of a reference input signal of the PLL and a frequency or a phase of an output signal of the PLL; means for sampling the error signal in accordance with the clock signal; means for determining a trend of the sampled error signal; means for comparing the trend of the sampled error signal to a previous trend of the sampled error signal to detect for a change in the trend of the sampled error signal; and means for initiating a change in a mode of operation of the PLL upon detecting the change in the trend of the sampled error signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification