Charge pump for phase locked loop with reduced leakage current

A phase locked loop comprising:

• a voltage-controlled oscillator configured to generate an oscillating signal output;
• a pre-scaler configured to scale the oscillating signal output as an output of the phase locked loop;
• a controller coupled to the output and configured to compare the output to a reference and to generate an up-control signal and a down control signal;
• and
• a charge pump configured to receive the up-control output and the down control output and to generate a control voltage in response thereto, the charge pump including:
• a main branch having two parallel lines of switches and a main branch output;
• a side branch coupled to the main branch having two parallel lines of switches and a side branch output;
• a charge pump output at which the main branch output and the side branch output are coupled together;
• and
• a variable resistor between the main branch and a ground and a side branch variable resistor between the side branch and ground,
• wherein the variable resistor and the side branch variable resistor are independently variable to adjust current flow to the charge pump output.

A method comprising:

• receiving a supply voltage at an input node of a charge pump;
• receiving an up-control signal at the charge pump;
• receiving a down control signal at the charge pump;
• activating a plurality of parallel up switches of a main branch of the charge pump in response to the up-control signal to charge a capacitor of an output filter;
• activating a plurality of parallel down switches of a main branch of the charge pump in response to the down control signal to discharge the capacitor;
• activating a plurality of parallel up switches of a side branch of the charge pump in response to the up-control signal to cancel leakage current from the main branch;
• and
• activating a plurality of parallel down switches of a side branch of the charge pump in response to the down control signal to cancel leakage current from the main branch.