Digital Phase Locked Loop and Method for Operating the Same
First Claim
1. A Digital Phase Locked Loop (DPLL) for phase locking an output signal to a reference clock signal, the DPLL comprising:
- a phase detector configured for detecting a phase error of a feedback signal with respect to the reference clock signal, wherein the feedback signal is the output signal of the DPPL fed back to an input of the phase detector, wherein the phase detector comprises;
an integer circuit configured for generating a first control signal representative of an integer phase error; and
a fractional circuit comprising a Time-to-Digital Converter (TDC) configured for processing the feedback signal and a delayed reference clock signal to generate a TDC output, wherein the fractional circuit is configured for generating from the TDC output a second control signal representative of a fractional phase error;
a digitally controlled oscillator (DCO) configured for generating the output signal based at least on a frequency control word and at least one control signal representative of the phase error detected by the phase detector; and
an unwrapping unit configured for unwrapping the TDC output.
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Abstract
The present disclosure relates to a Digital Phase Locked Loop (DPLL) for phase locking an output signal to a reference clock signal. The DPLL comprises a phase detector for detecting a phase error of a feedback signal with respect to the reference clock signal. The DPLL comprises a digitally controlled oscillator for generating the output signal based at least on a frequency control word and at least one control signal representative of the phase error. The phase detector comprises an integer circuit for generating a first control signal representative of an integer phase error. The phase detector comprises a fractional circuit comprising a Time-to-Digital Converter (TDC) for processing the feedback signal and a delayed reference clock signal. The fractional circuit is provided for generating from the TDC output a second control signal representative of a fractional phase error. The DPLL comprises an unwrapping unit for unwrapping the TDC output.
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Citations
18 Claims
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1. A Digital Phase Locked Loop (DPLL) for phase locking an output signal to a reference clock signal, the DPLL comprising:
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a phase detector configured for detecting a phase error of a feedback signal with respect to the reference clock signal, wherein the feedback signal is the output signal of the DPPL fed back to an input of the phase detector, wherein the phase detector comprises; an integer circuit configured for generating a first control signal representative of an integer phase error; and a fractional circuit comprising a Time-to-Digital Converter (TDC) configured for processing the feedback signal and a delayed reference clock signal to generate a TDC output, wherein the fractional circuit is configured for generating from the TDC output a second control signal representative of a fractional phase error; a digitally controlled oscillator (DCO) configured for generating the output signal based at least on a frequency control word and at least one control signal representative of the phase error detected by the phase detector; and an unwrapping unit configured for unwrapping the TDC output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for operating a Digital Phase Locked Loop (DPLL) for phase locking an output signal of the DPLL to a reference clock signal, the method comprising:
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supplying the reference clock signal to a first input of a phase detector of the DPLL; supplying the output signal of the DPLL as a feedback signal to a second input of the phase detector; generating, by an integer circuit of the phase detector, a first control signal representative of an integer phase error of the feedback signal with respect to the reference clock signal; processing, by a Time-to-Digital Converter (TDC) of a fractional circuit of the phase detector, the feedback signal and a delayed reference clock signal to generate a TDC output; generating from the TDC output a second control signal representative of a fractional phase error of the feedback signal with respect to the reference clock signal; unwrapping the TDC output using an unwrapping unit of the DPLL; regenerating the output signal of the DPLL using a digitally controlled oscillator (DCO) of the DPLL based at least on a frequency control word and at least one of the first control signal or the second control signal; obtaining initial phase locking of the output signal of the DPLL to the reference clock signal by repeating (a) the supplying of the output signal as the feedback signal to the phase detector, (b) the generating of the first control signal, (c) the processing by the TDC, (d) the generating of the second control signal, (e) the unwrapping of the TDC output, and (f) the regenerating of the output signal of the DPLL; deactivating the integer circuit of the phase detector after obtaining the initial phase locking; and tracking the phase locking of the output signal of the DPLL to the reference clock signal by repeating (a) the supplying of the output signal as the feedback signal to the phase detector, (b) the processing by the TDC, (c) the generating of the second control signal, (d) the unwrapping of the TDC output, and (e) the regenerating of the output signal of the DPLL. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification