A clock and data recovery circuit includes a sampling circuit, a phase detector, a first processing circuit, a second processing circuit and an oscillator circuit. The sampling circuit is configured to sample input data according to an output clock, and generate a sampling result. The phase detector is configured to generate a detection result according to the sampling result. The first processing circuit is configured to process the sampling result to generate a first digital code. The second processing circuit is configured to accumulate a portion of the first digital code to generate a second digital code. A rate of change of a code value of the second digital code is slower than a rate of change of a code value of the first digital code. The oscillator circuit is configured to generate the output clock according to the detection result, the first digital code and the second digital code.

The present invention discloses a clock data recovery method having quick locking and bandwidth stabilizing mechanism used in a clock data recovery circuit. A relative position relation between a serial data and a sampling clock is detected by a phase detection circuit in an adaptive control period to generate a tracking direction. The tracking direction of a first clock period is directly outputted as an adaptive tracking direction by an adaptive tracking circuit. For each of the clock periods behind the first clock period, a previous tracking direction is replaced by a current tracking direction only when the current tracking direction exists and is different from the previous tracking direction of a previous clock period such that an actual tracking direction is generated when the adaptive tracking direction changes. The phase of the sampling clock is adjusted according to the actual tracking direction by a clock control circuit.

The present invention discloses a clock data recovery method having quick locking and bandwidth stabilizing mechanism used in a clock data recovery circuit. A relative position relation between a serial data and a sampling clock is detected by a phase detection circuit in an adaptive control period to generate a tracking direction. The tracking direction of a first clock period is directly outputted as an adaptive tracking direction by an adaptive tracking circuit. For each of the clock periods behind the first clock period, a previous tracking direction is replaced by a current tracking direction only when the current tracking direction exists and is different from the previous tracking direction of a previous clock period such that an actual tracking direction is generated when the adaptive tracking direction changes. The phase of the sampling clock is adjusted according to the actual tracking direction by a clock control circuit.

A method for controlling a phase-locked loop circuit, can include: acquiring values of a voltage-controlled oscillator capacitor array control signal respectively corresponding to desired values of a frequency control word signal and acquiring values of a charge pump current control signal respectively corresponding to the desired values of the frequency control word signal in a calibration mode, where the frequency control word signal characterizes a ratio of a desired locked frequency to a frequency of a reference signal; and determining a target value of the voltage-controlled oscillator capacitor array control signal corresponding to a target value of the frequency control word signal and a target value of the charge pump current control signal corresponding to the target value of the frequency control word signal in a phase-locked mode, in order to control the phase-locked loop circuit to achieve phase lock.

A phase locked loop includes a pulse limiter between a phase frequency detector and a charge pump. The phase frequency detector generates and sends a clock pulse to the pulse limiter. The pulse limiter generates a first signal that indicates that the clock pulse is greater than a minimum pulse width of the phase frequency detector. The pulse limiter receives a pulse limiter buffer selection signal that selects one buffer of a plurality of buffers within the pulse limiter. The pulse limiter generates a second signal that indicates a truncated pulse width as the minimum pulse width of the phase frequency detector plus a delay period that is associated with the pulse limiter buffer selection signal. The pulse limiter truncates the clock pulse to the truncated pulse width and sends the truncated clock pulse to the charge pump.

A phased locked loop includes; a load circuit that generates an output signal in response to a driving voltage, a frequency calibration circuit that generates a calibration signal in response to an output frequency of the output signal and a target frequency, and a regulator that generates the driving voltage in response to the calibration signal.

A phase-locked loop (PLL) circuit generates an analog signal in phase-lock with a reference signal at a reference frequency. The PLL circuit includes a charge pump circuit, a loop filter circuit, a feedback divider, and a voltage controlled oscillator (VCO). The charge pump circuit charges a sample capacitor of the loop filter circuit to a sample voltage based on a phase difference between the generated analog signal and the reference signal. The loop filter circuit stores the sample voltage as a proportional control voltage in a hold capacitor to reduce or avoid ripple in the control voltage that causes jitter in the analog signal. The loop filter circuit also provides the sample voltage to an integral component circuit comprising a comparator and digital accumulator producing an integral control. The VCO generates the analog signal at a frequency based on the proportional control voltage and the integral control voltage.

A delay locked loop circuit includes a first delay locked loop and a second delay locked loop having different characteristics. The first delay locked loop performs a delay-locking operation on a reference clock signal to generate a delay locked clock signal. The second delay locked loop performs a delay-locking operation on the delay locked clock signal to generate an internal clock signal.

A delay locked loop circuit includes a first delay locked loop and a second delay locked loop having different characteristics. The first delay locked loop performs a delay-locking operation on a reference clock signal to generate a delay locked clock signal. The second delay locked loop performs a delay-locking operation on the delay locked clock signal to generate an internal clock signal.

A charge pump has a first branch that includes a first node connected between a first pull-up switch and a first pull-down switch and a second branch that includes a second node connected between a second pull-up switch and a second pull-down switch. The second branch is connected in parallel with the first branch. The charge pump has a voltage equalization circuit to equalize a first voltage at the first node and a second voltage at the second node. A third branch includes a third node that is connected between a third pull-up switch and a third pull-down switch. The third node is connected to the second node. The third pull-up switch and the first pull-up switch are controlled by a common pull-up signal. The third pull-down switch and the first pull-down switch are controlled by a common pull-down signal.