HYBRID PHASE-LOCKED LOOP
First Claim
Patent Images
1. A phase-locked loop (PLL), comprising:
- a phase detector configured to assert an up signal in response to a reference signal leading a feedback signal and to assert a down signal in response to the feedback signal leading the reference signal;
a time-to-digital converter configured to convert a phase difference between the assertion of the up signal and the assertion of the down signal into a digital code;
a digital filter configured to integrate the digital code into an integrated digital code;
a delta-sigma modulator configured to modulate the integrated digital code into a modulated digital code;
an integral digital-to-analog converter configured to convert the modulated digital code into an analog integral control signal;
a proportional digital-to-analog converter configured to convert the up signal and the down signal into an analog proportional control signal; and
an oscillator configured to produce a PLL output signal responsive to the analog proportional control signal and to the analog integral control signal.
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Abstract
A hybrid PLL is provided that includes an digital integral path and an analog proportional path.
17 Citations
20 Claims
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1. A phase-locked loop (PLL), comprising:
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a phase detector configured to assert an up signal in response to a reference signal leading a feedback signal and to assert a down signal in response to the feedback signal leading the reference signal; a time-to-digital converter configured to convert a phase difference between the assertion of the up signal and the assertion of the down signal into a digital code; a digital filter configured to integrate the digital code into an integrated digital code; a delta-sigma modulator configured to modulate the integrated digital code into a modulated digital code; an integral digital-to-analog converter configured to convert the modulated digital code into an analog integral control signal; a proportional digital-to-analog converter configured to convert the up signal and the down signal into an analog proportional control signal; and an oscillator configured to produce a PLL output signal responsive to the analog proportional control signal and to the analog integral control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of phase-locking an output signal to a reference signal, comprising;
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converting a phase difference between an up signal and a down signal into a digital code; integrating the digital code to produce an integrated digital code; delta-sigma modulating the integrated digital code to produce a modulated digital code; converting the modulated digital code into an analog integral control signal; converting the up signal and the down signal into an analog proportional control signal; controlling an oscillator responsive to the analog integral control signal and the analog proportional control signal to produce the output signal. - View Dependent Claims (15, 16, 17)
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18. A phase-locked loop (PLL), comprising:
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a phase detector configured to assert an up signal in response to a reference signal leading a feedback signal and to assert a down signal in response to the feedback signal leading the reference signal; a time-to-digital converter configured to convert a phase difference between the assertion of the up signal and the assertion of the down signal into a digital word and to offset the digital word by an offset to produce a digital code; means for integrating and converting the digital code to produce an analog integral control signal; a proportional digital-to-analog converter configured to convert the up signal and the down signal into an analog proportional control signal; a first current source configured to generate a first control current responsive to the analog integral control signal; a second current source configured to generate a second control current responsive to the analog proportional control signal; and a current-controlled oscillator configured to produce a PLL output signal responsive to the first control current and to the second control current. - View Dependent Claims (19, 20)
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Specification