Abstract: A PLL includes a phase frequency detector (PFD), a charge pump, a capacitor coupled to the charge pump, an analog-to-digital convertor (ADC), a noise canceller, an accumulator, a loop filter, an oscillator, a digital block and a frequency divider. The PFD detects a phase difference between a reference signal and a divided signal. The charge pump generates a charge pump signal in response to the phase difference. The ADC converts the charge pump signal to a first digital signal, and quantizes it to a second digital signal. The noise canceller forms a shaped noise signal according to the first and second digital signals, and eliminates the shaped noise signal at the output of the noise canceller to generate a noise cancelled signal. The accumulator accumulates the noise cancelled signal. The loop filter filters the accumulated signal. The oscillator provides an output oscillating signal in response to the filtered signal.

Abstract: A PLL includes a phase frequency detector (PFD), a charge pump, a capacitor coupled to the charge pump, an analog-to-digital convertor (ADC), a noise canceller, an accumulator, a loop filter, an oscillator, a digital block and a frequency divider. The PFD detects a phase difference between a reference signal and a divided signal. The charge pump generates a charge pump signal in response to the phase difference. The ADC converts the charge pump signal to a first digital signal, and quantizes it to a second digital signal. The noise canceller forms a shaped noise signal according to the first and second digital signals, and eliminates the shaped noise signal at the output of the noise canceller to generate a noise cancelled signal. The accumulator accumulates the noise cancelled signal. The loop filter filters the accumulated signal. The oscillator provides an output oscillating signal in response to the filtered signal.