Charge pump with low charge injection and low clock feed-through

A phase locked loop (PLL) comprising:

• a loop filter to generate an output voltage;
• a voltage controlled oscillator (VCO) coupled to an output of the loop filter, the voltage controlled oscillator to generate an output signal with a known relationship to an input reference signal, wherein the voltage controlled oscillator generates the output signal based on the output voltage from the loop filter;
• a detector coupled to an output of the voltage controlled oscillator, the detector to compare the output signal and the input reference signal and to generate at least one control signal to adjust the output signal generated by the voltage controlled oscillator;
• and
• a charge pump coupled between an output of the detector and an input of the loop filter, the charge pump to charge and discharge a load capacitor within the loop filter in response to the control signal from the detector, wherein the charge pump comprises:
• first and second current mirrors to serve as separate charge and discharge current sources, wherein each current mirror comprises a source MOS transistor and an output MOS transistor;
• and
• MOS tuners coupled to the first and second current mirrors, wherein each MOS tuner comprises a transistor with a source coupled to a source of the corresponding output MOS transistor, and a drain coupled to gates of the corresponding source and output MOS transistors.

A method for operating a charge pump of a phase locked loop (PLL), the method comprising:

• receiving a first tuning control signal;
• turning on a PMOS tuner in response to the first tuning control signal, wherein the PMOS tuner comprises a PMOS transistor with a source coupled to a source of an output PMOS transistor of a source-switched charging current mirror, and a drain coupled to a gate of the output PMOS transistor of the source-switched charging current mirror;
• receiving a charge control signal;
• and
• turning on a PMOS switch while the PMOS tuner is turned on, wherein the PMOS switch is coupled to the source of the PMOS tuner and to the source of the output PMOS transistor of the source-switched charging current mirror, wherein turning on the PMOS switch facilitates charging a load capacitor within a loop filter of the PLL.