Techniques for generating clock signals using counters
First Claim
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1. A circuit comprising:
- a phase detector that compares a phase of a first clock signal to a phase of a second clock signal;
a first counter that generates first count signals based on an output of the phase detector;
a second counter that generates second count signals;
a first comparator that generates a first comparison signal based on the first count signals and the second count signals, wherein the second clock signal is based on the first comparison signal;
a first oscillator that generates a first oscillator signal, wherein the second counter generates the second count signals based on the first oscillator signal;
a third counter that generates third count signals; and
a second comparator that generates a second comparison signal based on the first count signals and the third count signals, wherein the first oscillator generates oscillations in the first oscillator signal based on the second comparison signal.
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Abstract
The circuit, typically a delay-locked loop, comprises a phase detector, a first counter, a second counter, and a comparator. The phase detector compares a phase of a first clock signal with a phase of a second clock signal. The first counter generates first count signals and adjusts the first count signals when the phase detector indicates that the phases of the first and the second clock signals are out of alignment. The second counter generates second count signals. The first comparator generates a first comparison signal in response to a comparison between the first count signals and the second count signals. The second clock signal is generated in response to the first comparison signal.
22 Citations
24 Claims
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1. A circuit comprising:
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a phase detector that compares a phase of a first clock signal to a phase of a second clock signal; a first counter that generates first count signals based on an output of the phase detector; a second counter that generates second count signals; a first comparator that generates a first comparison signal based on the first count signals and the second count signals, wherein the second clock signal is based on the first comparison signal; a first oscillator that generates a first oscillator signal, wherein the second counter generates the second count signals based on the first oscillator signal; a third counter that generates third count signals; and a second comparator that generates a second comparison signal based on the first count signals and the third count signals, wherein the first oscillator generates oscillations in the first oscillator signal based on the second comparison signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A circuit comprising:
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a phase detector that compares a phase of a first clock signal to a phase of a second clock signal; a first counter that generates first count signals and that adjusts the first count signals when the phase detector indicates that the phases of the first and the second clock signals are out of alignment; a second counter that generates second count signals; a first comparator that generates a first comparison signal in response to a comparison between the first count signals and the second count signals, wherein the second clock signal is generated in response to the first comparison signal; a first oscillator that generates a first oscillator signal, wherein the second counter adjusts the second count signals in response to the first oscillator signal; a third counter that generates third count signals; a second oscillator that generates a second oscillator signal, wherein the third counter adjusts the third count signals in response to the second oscillator signal; and a second comparator that generates a second comparison signal in response to a comparison between at least a subset of the first count signals and the third count signals, wherein the first oscillator is enabled to generate oscillations in the first oscillator signal in response to the second comparison signal. - View Dependent Claims (9)
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10. A circuit comprising:
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a phase detector that compares a phase of a first clock signal to a phase of a second clock signal; a first counter that generates first count signals and that adjusts the first count signals when the phase detector indicates that the phases of the first and the second clock signals are out of alignment; a second counter that generates second count signals; a first comparator that generates a first comparison signal in response to a comparison between the first count signals and the second count signals, wherein the second clock signal is generated in response to the first comparison signal; and a third counter that generates a third clock signal by dividing a frequency of the first clock signal, wherein the first counter adjusts the first count signals in response to the third clock signal when the phases of the first and the second clock signals are out of alignment.
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11. A circuit comprising:
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a phase detector that compares a phase of a first clock signal with a phase of a second clock signal; a first counter that generates first count signals, wherein the first counter varies the first count signals to adjust the phase of the second clock signal and align the phases of the first and the second clock signals; a first oscillator that generates a first oscillator signal having a frequency that is independent of variations in a phase offset between the first and the second clock signals; a second counter that generates second count signals, wherein the second counter adjusts the second count signals in response to the first oscillator signal; and a first comparator that generates a first comparison signal in response to a comparison between the first count signals and the second count signals, wherein the second clock signal is generated in response to the first comparison signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for generating an output clock signal, the method comprising:
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comparing a phase of a first clock signal with a phase of a second clock signal; generating first count signals; varying the first count signals when the phases of the first and the second clock signals are out of alignment; generating second count signals; generating a first comparison signal in response a comparison between the first count signals and the second count signals; generating the second clock signal in response to the first comparison signal; generating a first oscillator signal; varying the second count signals in response to the first oscillator signal; generating third count signals; generating a second comparison signal based on a comparison between at least a subset of the first count signals and the third count signals; and enabling an oscillator to generate oscillations in the first oscillator signal based on the second comparison signal. - View Dependent Claims (22, 23)
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24. A method comprising:
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comparing a phase of a first clock signal with a phase of a second clock signal using a phase detector; varying first count signals generated by a first counter based on an output of the phase detector; generating a first oscillator signal; generating second count signals based on the first oscillator signal using a second counter; generating a first comparison signal based on the first count signals and the second count signals, wherein the second clock signal is generated in response to the first comparison signal; generating third count signals using a third counter; and generating a second comparison signal based on the first count signals and the third count signals, wherein generating a first oscillator signal comprises generating oscillations in the first oscillator signal based on the second comparison signal.
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Specification