Patent ID: 6985708

Claim:
A fractional-N synthesizer comprises: phase and frequency detection module operably coupled to produce a charge up signal, a charge down signal, or an off signal based on at least one of a phase difference and a frequency difference between a reference oscillation and a feedback oscillation; charge pump circuit produces a positive current in response to the charge up signal, a negative current in response to the charge down signal, and zero current in response to the off signal; gated current offset module operably coupled to cyclically provide a gated offset current based on the reference oscillation wherein the gated current offset module includes: current source operably coupled to cyclically source current to the loop filter; switch operable to couple the current source to the loop filter in accordance with a gate control signal; and control module operably coupled to generate the gate control signal based on the reference oscillation and predetermined duty cycle such that the gated offset current is aligned with the negative current; loop filter operably coupled to filter at least some of: the positive current, the negative current, the zero current, and the gated offset current to produce a control voltage; voltage controlled oscillator to produce an output oscillation based on the control voltage; and fractional-N divider module operably coupled to divided the output oscillation by a fractional N value to produce the feedback oscillation.