PLL frequency synthesizer

A PLL frequency synthesizer comprising:

• reference oscillator means for generating a signal having a reference frequency;
• VCO means for generating an oscillation of a frequency varying in response to a control voltage;
• phase comparator means for comparing the output phases of said reference oscillator means and said VCO means and generating an output corresponding to a phase difference between these output phases;
• charge pump means provided with power supply and responsive to the output of said phase comparator means to provide a pumping voltage;
• filter means for filtering said pumping voltage and supplying the resultant to said VCO means as said control voltage;
• and
• booster means for boosting the output of said reference oscillator and supplying the boosted output to said charge pump means.

A method for use in a PLL frequency synthesizer, for controlling the oscillation frequency of a VCO, comprising the following steps of:

• generating from said VCO a first signal having a frequency corresponding to a control voltage;
• generating a reference signal having a prescribed frequency;
• comparing said first signal and said reference signal, and outputting a second signal according to a phase difference therebetween;
• boosting the voltage of said reference signal to provide a boosted D.C. voltage;
• charging and discharging a first capacitor with said boosted D.C. voltage in response to said second signal;
• and
• supplying the terminal voltage of said first capacitor to said VCO as said control voltage.

A method for use in a PLL frequency synthesizer, for controlling the oscillation frequency of a VCO, comprising the following steps of:

• generating a first signal having a frequency corresponding to a control voltage;
• dividing the frequency of said first signal in a ratio according to a control signal;
• generating a reference signal having a prescribed frequency;
• dividing the frequency of said reference signal in a fixed ratio;
• comparing the phases of signals resulting from frequency divisions in said ratio according to said control signal and in said fixed ratio, and outputting a control pulse corresponding to a phase difference between these signals;
• generating a charge/discharge voltage according to said control pulse;
• charging or discharging a first capacitor with said charge/discharge voltage and generating a voltage across said first capacitor as said control voltage;
• and
• boosting the voltage of said signal frequency-divided in said fixed ratio, and using the boosted voltage as said charge/discharge voltage.