A frequency synthesizer includes an oscillator for providing an RF clock, a phase shifter coupled to said oscillator for providing a shifted RF clock by changing phase of said RF clock, and a time-to-digital converter (TDC) coupled to said phase shifter for quantizing a time difference between a frequency reference clock and said shifted RF clock, wherein a range of said TDC covers significantly less than a full range of said RF clock period. An associated method is also provided.