Back to results
US 6,046,646 AGranted
Modulation of a phase locked loop for spreading the spectrum of an output clock signal
OwnerPedro W. Lo, Gregory J. Richmondinventors
Life of this patent
Estimating the term…
Abstract
Apparatus and methods for controlling the frequency spectrum of a clock signal, for example, to reduce EMI emissions. A PLL circuit receives a reference signal and generates an output clock signal. A modulating circuit is coupled to the PLL and generates a modulating signal. The PLL receives the modulating signal and accordingly varies the frequency spectrum of the output clock signal.
Claims24
An apparatus for spreading a frequency spectrum of a reference signal comprising:
- a phase-locked loop circuit configured to receive the reference signal and to generate an output signal;
- and
- a modulating circuit coupled to the phase-locked loop, configured to receive the reference signal and to generate a modulating signal based on the reference signal, the phase-locked loop configured to vary the frequency spectrum of the output signal in accordance with a value of the modulating signal,
- wherein the phase-locked loop includes a potential storage device configured to receive the modulating signal, the modulating circuit configured to charge and discharge the potential storage device in accordance with the modulating signal.
1 more element
An apparatus for spreading a frequency spectrum of a reference signal comprising:
- a phase-locked loop circuit configured to receive the reference signal and to generate an output signal;
- and
- a modulating circuit coupled to the phase-locked loop, configured to receive the reference signal and to generate a modulating signal based on the reference signal, the phase-locked loop configured to vary the frequency spectrum of the output signal in accordance with a value of the modulating signal, wherein the modulating circuit includes:
- a modulator configured to receive the reference signal and to generate a modulation control signal;
- and
- a modulation charge pump coupled to the modulator and configured to receive the modulation control signal, the charge pump generating the modulating signal.
3 more elements
An apparatus for spreading a frequency spectrum of a reference signal comprising:
- a phase-locked loop circuit configured to receive the reference signal and to generate an output signal;
- a modulating circuit coupled to the phase-locked loop, configured to receive the reference signal and to generate a modulating signal based on the reference signal, the phase-locked loop configured to vary the frequency spectrum of the output signal in accordance with a value of the modulating signal;
- a signal divider coupled to the phase-locked loop and the modulating circuit, the signal divider configured to receive the output signal and a start signal generated by the modulating circuit, the modulating circuit start signal indicating when the signal divider should begin counting pulses present in the output signal, the signal divider generating an output indicative of an average value of a frequency of the output signal;
- and
- a signal detector coupled to the modulating circuit and the signal divider, the signal detector configured to generate a control signal based on comparing the signal divider output signal and a modulation frequency signal from the modulating circuit, the phase-locked loop configured to adjust the modulating signal in accordance with the signal detector control signal.
2 more elements
An circuit for spreading a frequency spectrum of a reference signal comprising:
- a phase-locked loop circuit configured to receive the reference signal and to generate an output signal;
- a modulator configured to receive the reference signal and to generate a modulation control signal;
- a modulation charge pump coupled to the modulator and configured to receive the modulation control signal, the charge pump generating a modulating signal;
- a first potential storage device coupled to the modulation charge pump, configured to receive the modulating signal, the charge pump configured to charge and discharge the first potential storage device in accordance with the modulating signal;
- a signal divider coupled to the phase-locked loop and the modulator, the signal divider configured to receive the output signal and a start signal generated by the modulator, the modulator start signal indicating when the signal divider should begin counting pulses present in the output signal, the signal divider generating an output indicative of an average value of a frequency of the output signal;
- a signal detector coupled to the modulator and the signal divider, the signal detector configured to generate a control signal based on comparing the signal divider output signal and a modulation frequency signal from the modulator;
- a control charge pump coupled to the modulation charge pump and the signal detector, configured to receive the signal detector control signal and to supply a pump signal to the modulation charge pump;
- and
- a second potential storage device coupled to the modulation charge pump and the control charge pump, configured to receive the pump signal, the control charge pump configured to charge and discharge the second potential storage device in accordance with the pump signal, the modulation charge pump configured to adjust the modulating signal in accordance with a value of potential stored in the second potential storage device.
6 more elements
A method for spreading a frequency spectrum of a reference signal comprising:
- receiving the reference signal;
- deriving an output signal from the reference signal by locking onto a characteristic of the reference signal, wherein the reference signal characteristic is selected from a group comprising signal phase and signal frequency;
- deriving a modulating signal from the reference signal;
- controlling a frequency spectrum of the output signal in accordance with the modulating signal;
- generating a count pulse for a count signal whenever a selected number of cycles of the output signal is reached during a first period;
- deriving a modulation frequency signal from the reference signal;
- generating a detector control signal based on a comparison of the count signal and the modulation frequency signal;
- and
- controlling the modulating signal based on the detector control signal.
6 more elements
Dependencies are inferred from the claim text.