Patent ID: 8552774

Claim:
A circuit comprising: a voltage controlled oscillator to generate an output clock signal of variable frequency in response to a direct current control voltage; a frequency divider coupled to the voltage controlled oscillator, the frequency divider configured to divide down a frequency of the output clock signal to generate a frequency divided output signal; a phase frequency detector coupled to the frequency divider and configured to compare a phase and frequency of a reference clock signal with a phase and frequency of the frequency divided output signal to generate frequency control signals; and a charge pump configured to generate an output control voltage based on the frequency control signals, the charge pump having a first auxiliary switching transistor and a second auxiliary switching transistor that are coupled in series between a first intermediate node of a plurality of series coupled transistors and a second intermediate node of the plurality of series coupled transistors, the first auxiliary switching transistor and the second auxiliary switching transistor to switch on to provide an equalization path between the first intermediate node and the second intermediate node to reduce noise in the output of the charge pump, wherein the charge pump further includes: a biased transistor having a terminal coupled to the first intermediate nodes; a gate terminal coupled to an output of an operational amplifier; a first main switching transistor having a first terminal coupled to a positive power supply and a second terminal coupled to the first intermediate node; a second main switching transistor coupled to ground; and a second biased transistor coupled between a charge pump output terminal of the charge pump and the second main switching transistor, wherein a second terminal of the biased transistor is coupled to the charge pump output terminal of the charge pump, and wherein the first main switching transistor and the second main switching transistor are configured to charge the charge pump output terminal of the charge pump.