Patent ID: 8067988

Claim:
A frequency synthesizer, comprising: a detector, for generating a detection signal based on a logic level difference between an input signal and a feedback signal; a charge pump, connected to the detector, for generating a control signal based on the detection signal; a low pass filter connected to the charge pump, for generating a tuning signal based on the control signal; a bias circuit connected to the low pass filter, for generating a first bias signal and a second bias signal based on the tuning signal; a controllable oscillator, connected to the bias circuit, for generating a differential output signal based on the first and the second bias signals, the controllable oscillator including an oscillator comprised of a plurality of delay cells, and a capacitance bank controller for controlling the delay cells to generate the differential output signal for further selecting a specific frequency thereby dynamically providing load capacitance to the plurality of delay cells and filtering out phase errors of the controllable oscillator; a differential-to-single-ended converter, connected to the controllable oscillator, for converting the differential output signal into an output signal; and a programmable frequency divider, connected to the differential-to-single-ended converter, for generating the feedback signal based on the output signal, wherein the LPF comprises a first capacitor, a second capacitor and a first resistor, the second capacitor has a first end connected through a terminal to the charge pump and a first end of the first resistor and a second end connected to a low voltage, the first resistor has a second end connected to a first end of the first capacitor, and the first capacitor has a second end connected to the low voltage.