The invention provides a frequency
discriminator, a PAM4
clock data frequency locking method, a PAM4
clock data frequency
recovery method and a PAM4
clock data frequency locking circuit. The method comprises the following steps: respectively sampling data and edges of an input
signal by adopting a data and edge sampling clock; Obtaining a logic result of the speed of the sampling clock according to the sampling data of at least two adjacent clock periods and the sampling edge between the two sampling data; Determining the frequency of the sampling clock relative to the input
signal based on the logic results of at least three adjacent clock periods, and enabling the frequency of the sampling clock to be equal to that of the input
signal; based on the Bang-Bang logics, adjusting the phase of the sampling clock, so that the sampling edge of the sampling clock is respectively positioned in the data of the input signal and the middle area of the edge. The non-reference clock frequency locking and
phase locking technology is adopted, so that the frequency and the phase can be accurately locked; The requirement for the
frequency difference between the starting frequency of the
voltage-controlled oscillator and an input signal is low, the clock
data recovery function of the large-range input
data rate can be supported, the application range is wide, and the stability is high.