Phase-lock loop with independent phase and frequency adjustments
First Claim
1. A system for generating an internal clock signal in response to an external clock signal, comprising:
- a phase adjustment circuit responsive to said external clock signal and said internal clock signal for producing a phase adjustment signal representing a difference between the phase of said external clock signal and the phase of said internal clock signal;
a frequency adjustment circuit responsive to said external clock signal and said internal clock signal for producing a frequency adjustment signal representing a difference between the frequency of said external clock signal and the frequency of said internal clock signal;
a control value calculator responsive to said phase adjustment signal and said frequency adjustment signal for producing a resulting control signal; and
a signal-controlled oscillator responsive to said resulting control signal for producing said internal clock signal at an internal clock frequency deviating in response to said resulting control signal;
wherein said frequency adjustment circuit comprises a frequency detector responsive to said external clock signal and said internal clock signal for producing an instantaneous value of a frequency error signal indicating a difference between instantaneous frequencies of the internal clock signal and the external clock signal, and an accumulator coupled to said frequency detector for accumulating instantaneous values of the frequency error signal over a preset time period to produce an accumulated signal indicating an average value of the frequency difference for the preset time period.
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Accused Products
Abstract
A PLL is provided with separate phase and frequency adjustment circuits to adjust the frequency of a produced internal clock independently from adjusting its phase. The phase adjustment circuit determines a phase error between the internal clock and an external clock, and averages the phase error over a predetermined time period to produce the corresponding control current. The frequency adjustment circuit detects the difference between the frequency of the internal clock and the frequency of the external clock to determine a frequency error. An accumulator accumulates the frequency error during the predetermined time period to produce the corresponding control current. Based on values of the control currents produced by the phase and frequency adjustment circuits, a current calculator calculates a resulting value of the control current to be applied to a CCO to modify its frequency so as reduce the frequency and phase differences.
67 Citations
45 Claims
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1. A system for generating an internal clock signal in response to an external clock signal, comprising:
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a phase adjustment circuit responsive to said external clock signal and said internal clock signal for producing a phase adjustment signal representing a difference between the phase of said external clock signal and the phase of said internal clock signal;
a frequency adjustment circuit responsive to said external clock signal and said internal clock signal for producing a frequency adjustment signal representing a difference between the frequency of said external clock signal and the frequency of said internal clock signal;
a control value calculator responsive to said phase adjustment signal and said frequency adjustment signal for producing a resulting control signal; and
a signal-controlled oscillator responsive to said resulting control signal for producing said internal clock signal at an internal clock frequency deviating in response to said resulting control signal;
wherein said frequency adjustment circuit comprises a frequency detector responsive to said external clock signal and said internal clock signal for producing an instantaneous value of a frequency error signal indicating a difference between instantaneous frequencies of the internal clock signal and the external clock signal, and an accumulator coupled to said frequency detector for accumulating instantaneous values of the frequency error signal over a preset time period to produce an accumulated signal indicating an average value of the frequency difference for the preset time period. - View Dependent Claims (2)
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3. A system for generating an internal clock signal in response to an external clock signal, comprising:
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a phase adjustment circuit responsive to said external clock signal and said internal clock signal for producing a phase adjustment signal representing a difference between the phase of said external clock signal and the phase of said internal clock signal;
a frequency adjustment circuit responsive to said external clock signal and said internal clock signal for producing a frequency adjustment signal representing a difference between the frequency of said external clock signal and the frequency of said internal clock signal;
a control value calculator responsive to said phase adjustment signal and said frequency adjustment signal for producing a resulting control signal; and
a signal-controlled oscillator responsive to said resulting control signal for producing said internal clock signal at an internal clock frequency deviating in response to said resulting control signal, wherein said frequency adjustment circuit comprises a first counter responsive to said external clock signal and said internal clock signal for counting the number of cycles of the external clock signal during a half cycle of the internal clock signal in which the internal clock signal is at a first logic level. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A system for generating an internal clock signal in response to an external clock signal, comprising:
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a phase adjustment circuit responsive to said external clock signal and said internal clock signal for producing a phase adjustment signal representing a difference between the phase of said external clock signal and the phase of said internal clock signal;
a frequency adjustment circuit responsive to said external clock signal and said internal clock signal for producing a frequency adjustment signal representing the difference between a frequency of said external clock signal and the frequency of said internal clock signal;
a control value calculator responsive to said phase adjustment signal and said frequency adjustment signal for producing a resulting control signal; and
a signal-controlled oscillator responsive to said resulting control signal for producing said internal clock signal at an internal clock frequency deviating in response to said resulting control signal, wherein said frequency adjustment circuit comprises a first frequency divider supplied with said internal clock signal for producing a divided internal clock signal at a frequency equal to the frequency of the internal clock signal divided by a preset number, a second frequency divider supplied with said external clock signal for producing a divided external clock signal at a frequency equal to the frequency of the external clock signal divided by the preset number, and a first counter coupled to said first frequency divider and supplied with said external clock signal for counting the number of cycles of the external clock signal in a half cycle of the divided internal clock signal. - View Dependent Claims (14, 15, 16, 17)
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18. A system for generating an internal clock signal in response to an external clock signal, comprising:
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a phase adjustment circuit responsive to said external clock signal and said internal clock signal for producing a phase adjustment signal representing a difference between the phase of said external clock signal and the phase of said internal clock signal;
a frequency adjustment circuit responsive to said external clock signal and said internal clock signal for producing a rough frequency adjustment signal representing a difference between the frequency of said external clock signal and the frequency of said internal clock signal;
a control value calculator responsive to said phase adjustment signal and said rough frequency adjustment signal for producing a resulting control signal;
a signal-controlled oscillator responsive to said resulting control signal for producing said internal clock signal at an internal clock frequency deviating in response to said resulting control signal; and
a fine adjustment circuit supplied with said external clock signal for providing a fine frequency tuning signal to said control value calculator, in addition to the rough frequency adjustment signal provided by said frequency adjustment circuit, and the phase adjustment signal provided by said phase adjustment circuit. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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40. A method of producing an internal clock signal in synchronization with an external clock signal, comprising the steps of:
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comparing the phase of said internal clock signal with the phase of said external clock signal to produce a phase adjustment signal representing differences in phase and frequency between said internal clock signal and said external clock signal, comparing the frequency of said internal clock signal with the frequency of said external clock signal independently from said step of phase comparing, to produce a frequency adjustment signal representing the difference between the frequency of said internal clock signal and the frequency of said external clock signal;
producing a control signal representing said phase adjustment signal and said frequency adjustment signal;
controlling a signal-controlled oscillator by said control signal to produce said internal clock signal synchronized with said external clock signal, wherein said steps of phase comparing and frequency comparing are carried out by separate circuits; and
furtherfine tuning said signal-controlled oscillator when the frequency of said internal clock signal is close to the frequency of said external clock signal, wherein said step of fine tuning comprises a step of delaying the external clock signal by a delay time corresponding to a period of said internal clock signal. - View Dependent Claims (41, 42)
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43. A system for generating an internal clock signal in response to a reference clock signal, comprising:
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a phase adjustment circuit responsive to said reference clock signal and said internal clock signal for producing a phase adjustment signal representing a difference between the phase of said reference clock signal and the phase of said internal clock signal;
a frequency adjustment circuit responsive to said reference clock signal and said internal clock signal for producing a frequency adjustment signal representing a difference between the frequency of said reference clock signal and the frequency of said internal clock signal;
a control value calculator responsive to said phase adjustment signal and said frequency adjustment signal for producing a resulting control signal; and
a signal-controlled oscillator responsive to said resulting control signal for producing said internal clock signal at an internal clock frequency deviating in response to said resulting control signal, said frequency adjustment circuit including counter circuitry responsive to said reference clock signal and said internal clock signal for counting the number of cycles of said reference clock signal and said internal clock signal whichever is greater in frequency in a predetermined number of cycle(s) of said reference clock signal and said internal clock signal whichever is smaller in frequency, even when a relation in magnitude of frequency between the reference clock signal and the internal clock signal is changed. - View Dependent Claims (44)
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45. A system for generating an internal clock signal in response to a reference clock signal, comprising:
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a phase adjustment circuit responsive to said reference clock signal and said internal clock signal for producing a phase adjustment signal representing a difference between the phase of said reference clock signal and the phase of said internal clock signal;
a frequency adjustment circuit responsive to said reference clock signal and said internal clock signal for producing a frequency adjustment signal representing a difference between the frequency of said reference clock signal and the frequency of said internal clock signal;
a control value calculator responsive to said phase adjustment signal and said frequency adjustment signal for producing a resulting control signal; and
a signal-controlled oscillator responsive to said resulting control signal for producing said internal clock signal at an internal clock frequency deviating in response to said resulting control signal, said frequency adjustment circuit including counter circuitry responsive to said reference clock signal and said internal clock signal for counting the number of cycles of said reference clock signal in a predetermined window period, regardless of which of the reference clock signal and the internal clock signal is greater in frequency, said predetermined window period being N time(s) the cycle period of said internal clock signal even when a relation in frequency magnitude between the reference clock signal and the internal clock signal is changed, with N being an integer.
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Specification