Serializer-deserializer clock and data recovery gain adjustment

A method of adjustment of a voltage-controlled oscillator voltage-controlled oscillator based clock and data recovery circuit, the method comprising the steps of:

• detecting a phase difference signal between an input signal and a feedback signal by a phase detector;
• combining the phase difference signal with gear shifting control signals produced by a gear shifting control module to provide a first control signal for a voltage-controlled oscillator;
• integrating the phase difference signal to a second control signal by an integrator for the voltage-controlled oscillator;
• dividing an output of the voltage-controlled oscillator to multiple phase signals, wherein one of the multiple phase signals is coupled to a frequency calibration module as a calibrated reference frequency, another one of the multiple phase signals is sent back to the phase detector as the feedback signal, wherein the calibrating reference frequency is compared to a reference clock frequency from a reference clock to the frequency calibration module over a period of time;
• preforming a coarse calibration to the calibrated reference frequency of the voltage-controlled oscillator with the frequency calibration module;
• performing a fine calibration to the calibrated reference frequency of the voltage-controlled oscillator with the frequency calibration module;
• creating a look-up table with fine calibration values generated by the frequency calibration module;
• adjusting the gain of the circuit by adjusting gear shifting up or down by calculating gear shifting gains of the gear shifting control signals employing the fine calibration values stored in the look-up table.

A non-transitory machine-readable storage medium, having encoded thereon program code, wherein, when the program code is executed by a machine, the machine implements a method for adjustment of a voltage-controlled oscillator based clock and data recovery circuit, comprising the steps of:

• detecting a phase difference signal between an input signal and a feedback signal by a phase detector;
• combining the phase difference signal with gear shifting control signal produced by a gear shifting control module to provide a first control signal for a voltage-controlled oscillator;
• integrating the phase difference signal with gear shifting control signal produced by a gear shifting control module to a second control signal by an integrator for the voltage-controlled oscillator;
• dividing an output of the voltage-controlled oscillator to multiple phase signals, wherein one of the multiple phase signals is coupled to a frequency calibration module as a calibrated reference frequency, another one of the multiple phase signals is sent back to the phase detector as the feedback signal, wherein the calibrating reference frequency is compared to a reference clock frequency from a reference clock to the frequency calibration module over a period of time;
• preforming a coarse calibration to the calibrated reference frequency of the voltage-controlled oscillator with the frequency calibration module;
• performing a fine calibration to the calibrated reference frequency of the voltage-controlled oscillator with the frequency calibration module;
• creating a look-up table with fine calibration values generated by the frequency calibration module;
• adjusting the gain of the circuit by adjusting gear shifting up or down by calculating gear shifting gains of the gear shifting control signals employing the fine calibration values stored in the look-up table.