Phase-locked loop and method

A method of operating a phase-locked loop, the method comprising:

• receiving, by a phase frequency detector, a reference frequency and a feedback frequency;
• controlling, by an output of the phase frequency detector, a charge pump;
• receiving, by a low-pass analog filter, an output of the charge pump;
• delivering, by the low-pass analog filter, an analog control signal;
• delivering, by a controllable oscillator, an output frequency of the phase-locked loop;
• receiving, by a frequency divider, the output frequency;
• delivering, by the frequency divider, the feedback frequency;
• receiving, by a digital circuit, the reference frequency and the feedback frequency;
• delivering, by the digital circuit, a digital control signal;
• and
• determining, by the controllable oscillator, the output frequency at least partly by an analog frequency modulation signal, the analog control signal, and the digital control signal;
• wherein an open-loop gain of a digital loop is smaller than or equal to 1 for low frequencies lower than a unity frequency for which an open-loop gain of an analog loop is equal to 1, the digital loop comprising the frequency divider and the digital circuit, and the analog loop comprising the frequency divider, the phase frequency detector, the charge pump, and an analog filter.