A system for generating secondary clock signals from a primary clock signal includes a dithered clock divider which has a first input adapted to receive the primary clock signal and a second input adapted to receive a random division ratio. The dithered clock divider provides a dithered clock signal. The system includes a multi-phase clock generator which has a first input adapted to receive the primary clock signal, a second input adapted to receive the dithered clock signal, and a third input adapted to receive a pseudo-random pattern. The multi-phase clock generator provides the secondary clock signals from multiple phases of the dithered clock signal. The system includes a pseudo-random pattern generator which provides the pseudo-random pattern.

A system for generating secondary clock signals from a primary clock signal includes a dithered clock divider which has a first input adapted to receive the primary clock signal and a second input adapted to receive a random division ratio. The dithered clock divider provides a dithered clock signal. The system includes a multi-phase clock generator which has a first input adapted to receive the primary clock signal, a second input adapted to receive the dithered clock signal, and a third input adapted to receive a pseudo-random pattern. The multi-phase clock generator provides the secondary clock signals from multiple phases of the dithered clock signal. The system includes a pseuodo-random pattern generator which provides the pseudo-random pattern.

An analog PLL comprising: a VCO configured to provide a PLL output signal; a phase detector (PD) configured to receive a feedback signal from the VCO and a reference signal and wherein the PD provides a PD signal to a low pass filter (LPF), the LPF configured to filter of the PD signal and provide the filtered signal as a tuning voltage for the VCO; and a tracking loop configured to receive the tuning voltage and comprising at least a tracking loop comparator configured to provide a comparator output voltage based on a difference between the tuning voltage and a target voltage, wherein an output of the tracking loop provides a tracking voltage based on the comparator output voltage and wherein the frequency of the PLL output voltage is based on the tuning voltage and the tracking voltage.

A reference frequency signal generator comprises a plurality of ovenized reference crystal oscillators (OCXOs) having different turn-over-temperatures, a selector logic circuit coupled to outputs of the OCXOs, a temperature sensor, and a controller coupled to an output of the temperature sensor. The selector logic circuit outputs one of the outputs of the OCXOs based on a control signal from the controller. The controller also generates control signals for the OCXOs. In some implementations, the reference frequency signal generator includes a phase-locked loop or a fractional output divider coupled to the output of the selector logic circuit and configured to receive a calibration signal from the controller.

A system and method for a frequency detector circuit includes: a transition detector configured to receive a data input and provide a first edge output based on transitions in the data input; a first circuit configured to generate a second edge output; a second circuit configured to generate a third edge output; and a combinational logic configured to output an UP output when at least two of the first edge output, the second edge output, and the third edge output are high and configured to output a DOWN output when the first edge output, the second edge output, and the third edge output are all low.

A digital PLL circuitry, according to the present embodiment, includes: a phase difference arithmetic circuitry configured to arithmetically operate and output a phase difference between an input clock signal and an output clock signal; a first control code generation circuitry configured to generate a first control code for controlling an oscillation frequency based on the phase difference and a frequency control input being a control target frequency relating to the output clock signal, and output the first control code; a second control code generation circuitry configured to generate and output a second control code for controlling the oscillation frequency according to a sequence; a selection circuitry configured to select and output one of the first control code and the second control code as a selection control code; and a digitally controlled oscillator configured to output the output clock signal of the oscillation frequency according to the selection control code.

A PLL has a tunable resonator including an inductance and variable capacitance coupled between first and second nodes, and capacitances coupleable between the nodes. A control node is coupled to the variable capacitance and receives a control signal for tuning the resonator. A biasing circuit biases the resonator to generate an output. A PFD circuit senses timing offset of the output with respect to a reference and asserts first or second digital signals dependent on the sign of the timing offset. A charge pump generates the control signal based on the first and second digital signals. A timer asserts a timing signal in response to a pulse sensed in a reset signal and de-asserts the timing signal after a time interval. A calibrator couples selected capacitances between the first and second nodes as a function of the second digital signal, in response to assertion of the timing signal.

A computer system may periodically calibrate an oscillator subsystem, which includes a voltage-controlled oscillator circuit configured to generate an oscillator signal using code signal. In response to activation of a calibration mode, an iterative calibration operation may be performed on the voltage-controlled oscillator circuit. In some cases, performing a given iteration of the calibration operation includes determining a value of the code signal using a number of pulses in the oscillator signal sampled during a particular time period, along with previous values of the code signal and a slope of an error function associated with the difference between a desired frequency and a current frequency of the oscillator signal. In other cases, iterations may employ variable sampling times with error handling, in order to decrease the duration of the calibration operation while maintaining a target accuracy.

An equalizer control device includes a first circuit configured to, upon receipt of a data signal that has been equalized by a continuous time linear equalizer (CTLE) circuit, output a first signal related to a first number of times a waveform of the data signal crosses a threshold value or differential signals of the data signal cross each other. A second circuit is configured to count the first number during a particular time period based on the output first signal, and select one of equalization parameters to be set to the CTLE circuit based on the counted first number.

A computer system may periodically calibrate an oscillator subsystem, which includes a voltage-controlled oscillator circuit configured to generate an oscillator signal using code signal. In response to activation of a calibration mode, an iterative calibration operation may be performed on the voltage-controlled oscillator circuit. In some cases, performing a given iteration of the calibration operation includes determining a value of the code signal using a number of pulses in the oscillator signal sampled during a particular time period, along with previous values of the code signal and a slope of an error function associated with the difference between a desired frequency and a current frequency of the oscillator signal. In other cases, iterations may employ variable sampling times with error handling, in order to decrease the duration of the calibration operation while maintaining a target accuracy.