High gain low power phase detector and loop filter for phase lock loop (PLL)

An apparatus, comprising:

• a phase lock loop (PLL), comprising:
• a phase detector and loop pass filter (PD/LF), comprising:
• a phase/frequency detector including a first input configured to receive a reference signal, and a second input configured to receive a feedback signal, and an output configured to produce an output signal based on the reference and feedback signals;
• a first capacitor;
• and
• a charge pump, comprising:
• a charging path configured to generate a charging current to charge the first capacitor based on the output signal, the charging path comprises a current source and a first switching device coupled in series between an upper voltage rail and a first node, wherein an on/off state of the first switching device is controlled by the output signal of the phase/frequency detector, and wherein the first capacitor is coupled between the first node and the lower voltage rail;
• and
• a discharging path including a first resistor configured to discharge the first capacitor, the discharging path comprises the first resistor and a second switching device coupled in series between the first node and a lower voltage rail.

A method of generating a frequency control signal for a voltage controlled oscillator (VCO), comprising:

• generating a phase difference signal based on a reference signal and a feedback signal, wherein the feedback signal is based on a VCO signal generated by the VCO;
• partially discharging a first capacitor from a first voltage to a second voltage above ground potential during a discharging phase;
• charging the first capacitor from the second voltage to a third voltage based on the phase difference signal during a charging phase, wherein the frequency control signal is based on the third voltage;
• and
• distributing a charge on the first capacitor with a second capacitor when the first capacitor is charged to the third voltage, to form a fourth voltage across the first and second capacitors, wherein the frequency control signal is based on the fourth voltage.

An apparatus of generating a frequency control signal for a voltage controlled oscillator (VCO), comprising:

• means for generating a phase difference signal based on a reference signal and a feedback signal, wherein the feedback signal is based on a VCO signal generated by the VCO;
• means for partially discharging a first capacitor from a first voltage to a second voltage above ground potential during a discharging phase;
• means for charging the first capacitor from the second voltage to a third voltage based on the phase difference signal during a charging phase, wherein the frequency control signal is based on the third voltage;
• and
• means for distributing a charge on the first capacitor with a second capacitor when the first capacitor is charged to the third voltage, to form a fourth voltage across the first and second capacitors, wherein the frequency control signal is based on the fourth voltage.