Apparatus and method for combining multiple charge pumps in phase locked loops
AssigneeBroadcom Corporation
InventorGregory Alyn Unruh
Life of this patent
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Abstract
A frequency synthesizer includes circuitry configured to generate two or more feedback clocks based on the oscillation signals output from a voltage-controlled oscillator. The circuitry also modulates the feedback clocks based on fractional offsets from a reference clock frequency for input into two or more phase and frequency detectors. Multiple charge pump circuits receive inputs from these phase and frequency detectors. The current from these charge pumps is summed and input to a low pass filter. The output of the filter represents an average of the time difference between the reference clock and the multiple feedback clocks.
Claims19
A frequency synthesizer comprising:
- circuitry configured to
- generate two or more feedback clocks based on oscillation signals output from a voltage-controlled oscillator;
- modulate the two or more feedback clocks based on fractional offsets from a reference clock frequency for input into a plurality of phase and frequency detectors (PFDs) driving a plurality of charge pumps;
- and
- select an output from one of the plurality of PFDs corresponding to an early feedback clock input that leads a reference clock or a late feedback clock input that lags the reference clock to drive each of the plurality of charge pumps,
- wherein the circuitry is further configured to randomize selections of the plurality of charge pumps associated with the early feedback clock and late feedback clock.
A frequency synthesizer comprising:
- circuitry configured to
- generate two or more feedback clocks based on oscillation signals output from a voltage-controlled oscillator;
- modulate the two or more feedback clocks based on fractional offsets from a reference clock frequency for input into a plurality of phase and frequency detectors (PFDs) driving a plurality of charge pumps;
- and
- toggle between an early feedback clock and a late feedback clock driving the plurality of charge pumps based on a feedback clock selector signal.
A frequency synthesizer comprising:
- circuitry configured to
- generate two or more feedback clocks based on oscillation signals output from a voltage-controlled oscillator;
- modulate the two or more feedback clocks based on fractional offsets from a reference clock frequency for input into a plurality of phase and frequency detectors (PFDs) driving a plurality of charge pumps;
- and
- modulate an early feedback clock and a late feedback clock at equal and opposite phase and frequency offsets from a center frequency.
Dependencies are inferred from the claim text.