US Patent 11177812 Clock and data recovery circuit and frequency maintaining method

When digital input data disappear temporarily, within a counting period of the counter and pulse generator, an output voltage of the voltage generator rises, a threshold detector compares the output voltage of the voltage generator with a plurality of threshold values to generate a plurality of comparison results, and a logic gate unit generates a control signal according to the comparison results, to a charge pump, so that the charge pump controls the voltage-controlled oscillator to accelerate or decelerate.