Techniques for generating fractional periodic signals
First Claim
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1. A circuit comprising:
- a fractional phase-locked loop circuit comprising phase detection circuitry, an oscillator circuit that generates a first periodic signal, and a frequency divider circuit that divides a frequency of the first periodic signal by a frequency division value to generate a frequency of a second periodic signal, wherein the second periodic signal is provided to the phase detection circuitry; and
a delta sigma modulator circuit comprising a first accumulator that performs a first addition, first storage circuits that store signals based on the first addition received from the first accumulator, a first multiplexer that receives the signals based on the first addition from the first storage circuits and that provides one of the signals based on the first addition as a first selected signal, and a logic circuit that controls the frequency division value based on the first selected signal.
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Abstract
A demultiplexer circuit separates input data having different data rates into output data. A phase-locked loop circuit generates first clock signals having average frequencies that are based on a frequency of a second clock signal times a fractional, non-integer number. A serializer circuit serializes a set of the output data to generate serial data signals in response to one of the first clock signals generated by the phase-locked loop circuit.
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Citations
20 Claims
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1. A circuit comprising:
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a fractional phase-locked loop circuit comprising phase detection circuitry, an oscillator circuit that generates a first periodic signal, and a frequency divider circuit that divides a frequency of the first periodic signal by a frequency division value to generate a frequency of a second periodic signal, wherein the second periodic signal is provided to the phase detection circuitry; and a delta sigma modulator circuit comprising a first accumulator that performs a first addition, first storage circuits that store signals based on the first addition received from the first accumulator, a first multiplexer that receives the signals based on the first addition from the first storage circuits and that provides one of the signals based on the first addition as a first selected signal, and a logic circuit that controls the frequency division value based on the first selected signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method comprising:
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generating a first periodic signal using an oscillator circuit; dividing a frequency of the first periodic signal by a frequency division value to generate a frequency of a second periodic signal using a frequency divider circuit; providing the second periodic signal to phase detection circuitry, wherein the oscillator circuit, the frequency divider circuit, and the phase detection circuitry are part of a fractional phase-locked loop circuit; performing a first addition using a first accumulator; receiving signals that indicate a sum of the first addition at a first multiplexer and providing one of the signals that indicate the sum of the first addition as a first selected signal; controlling the frequency division value based on the first selected signal using a logic circuit, wherein the first accumulator, the first multiplexer, and the logic circuit are part of a delta sigma modulator circuit; and changing the one of the signals that indicate the sum of the first addition provided by the first multiplexer as the first selected signal to adjust a precision of an average frequency of the first periodic signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A circuit comprising:
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a fractional phase-locked loop circuit comprising phase detection circuitry, an oscillator circuit that generates a first periodic signal, and a frequency divider circuit that divides a frequency of the first periodic signal by a frequency division value to generate a frequency of a second periodic signal, wherein the second periodic signal is provided to the phase detection circuitry; and a delta sigma modulator circuit comprising a first accumulator that performs a first addition, a first multiplexer that receives signals based on the first addition and that provides one of the signals based on the first addition as a first selected signal, a second accumulator that performs a second addition, a second multiplexer that receives signals based on the second addition and that provides one of the signals based on the second addition as a second selected signal, and a logic circuit that generates the frequency division value by performing a mathematical function on values of the first and the second selected signals.
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Specification