Voltage controlled oscillator with reduced parasitic interference
AssigneeSTMicroelectronics S.r.l.
InventorPhilippe Sirito-Olivier
Life of this patent
Estimating the term…
Abstract
A phase locked loop for a voltage controlled oscillator includes a phase comparator receiving at its inputs a reference frequency signal and a frequency signal from the oscillator, and supplies logic values to command a charge pump. A charge re-injection circuit receives one of the inputs of the comparator and supplies a logic value to command the charge pump. The loop further includes a detector with a threshold value for a current representative of the current supplied by the charge pump. A logic output from the detector is applied to the charge re-injection circuit so that the duration of the charge re-injection is limited.
Claims31
A phase locked loop for a voltage controlled oscillator comprising:
- a charge pump;
- a phase comparator having a first input for receiving a reference frequency signal and a second input for receiving a frequency signal from the voltage controlled oscillator, and a first output for supplying a first logic pulse to command said charge pump;
- a charge re-injection circuit having an input connected to the second input of said phase comparator for receiving the frequency signal, and an output for supplying a second logic pulse to command said charge pump;
- and
- a current detector having a threshold representative of a current supplied by said charge pump, said current detector having an input connected to an output of said charge pump, and an output for applying a logic output pulse to said charge re-injection circuit for adjusting duration of the second logic pulse.
A phase locked loop comprising:
- a voltage controlled oscillator;
- a charge pump for providing a current to said voltage controlled oscillator;
- a phase comparator having a first input for receiving a reference frequency signal and a second input for receiving a frequency signal from said voltage controlled oscillator, and a first output for supplying a first logic pulse to command said charge pump;
- a charge re-injection circuit having an input connected to the second input of said phase comparator for receiving the frequency signal, and an output for supplying a second logic pulse to command said charge pump;
- a logic gate having a first input connected to the output of said charge re-injection circuit, a second input connected to the first output of said phase comparator, and an output connected to an input of said charge pump;
- and
- a current detector having a threshold representative of the current supplied by said charge pump, said current detector having an input connected to an output of said charge pump and an output for applying a logic output pulse to said charge re-injection circuit for adjusting duration of the second logic pulse.
A phase locked loop comprising:
- a voltage controlled oscillator;
- a first charge pump for providing a first current to said voltage controlled oscillator;
- a second charge pump for providing a second current;
- a phase comparator having a first input for receiving a reference frequency signal and a second input for receiving a frequency signal from said voltage controlled oscillator, and a first output for supplying a first logic pulse to command said first and second charge pumps;
- a charge re-injection circuit having an input connected to the second input of said phase comparator for receiving the frequency signal, and an output for supplying a second logic pulse to command said first and second charge pumps;
- a logic gate having a first input connected to the output of said charge re-injection circuit, a second input connected to the first output of said phase comparator, and an output connected to said first and second charge pumps;
- and
- a current detector having a threshold representative of the current supplied by said first and second charge pumps, said current detector having an input connected to an output of said second charge pump and an output for applying a logic output pulse to said charge re-injection circuit for adjusting duration of the second logic pulse.
A method of reducing parasitic interference supplied by a voltage controlled oscillator, the method comprising:
- comparing a phase between a reference frequency signal and a frequency signal from the voltage controlled oscillator;
- generating a first logic pulse to command a charge pump based upon comparing the phase;
- generating a second logic pulse to command the charge pump based upon the frequency signal from the voltage controlled oscillator;
- detecting a current supplied by the charge pump and comparing the detected current to a threshold for generating a logic output pulse;
- and
- adjusting duration of the second logic pulse based upon generation of the logic output pulse.
Dependencies are inferred from the claim text.