A phase-locked loop (PLL) may include a phase-frequency detector (PFD), a phase interpolation (PI)-based sampler, a loop filter, a voltage-controlled oscillator (VCO), and a fractional frequency divider. The PFD output corresponds to a phase error between a reference clock signal and a feedback signal. The PI-based sampler produces a slope signal in response to the PFD output, and adjusts the slope signal in response to a quantization error correction indication. The PI-based sampler also samples the slope signal. The loop filter produces a VCO control signal in response to a sampled slope signal. The VCO control signal controls the VCO frequency. The fractional frequency divider circuit divides the frequency of the VCO output signal and also determines the quantization error correction corresponding to the quantization error introduced by fractional division of the frequency of the VCO output signal.

The present invention relates to data communication and electrical circuits. More specifically, embodiments of the present invention provide a clock and data recovery (CDR) architecture implementation for high data rate wireline communication links. In an embodiment, a CDR device includes a phase detector, a loop filter, and a fractional-N PLL. The fractional-N PLL generates output clock signal based on output of the loop filter. There are other embodiments as well.

A PLL circuit includes a fractional-N divider generating a feedback signal, a first phase-frequency detector that compares the feedback signal to a reference signal to generate first up/down control signals that control a charge pump to generate a charge pump output current. A noise cancelation circuit includes a synchronization circuit that generates first and second synchronized feedback signals from the PLL circuit output and the feedback signal, where the first and second synchronized feedback signals are offset by an integer number of cycles of the PLL circuit output. A second phase-frequency detector circuit compares the first and second synchronized feedback clock signals to generate second up/down control signals whose pulse widths differ by the integer number of PLL cycles. A current digital to analog converter circuit is controlled in response to the second up/down control signals to apply noise canceling sourcing and sinking currents to the charge pump output current.

An electronic device includes a phase locked loop configured to perform a two-point modulation operation on a data signal by using first and second modulation paths, and the phase locked loop is configured to generate, based on a differential value of a first phase error signal generated in the first modulation path, a gain for adjusting a frequency variation of the data signal through the second modulation path so as to match with the frequency variation of the data signal through the first modulation path.

A frequency synthesizer includes a clock multiplier unit configured to receive a first clock and output a second clock in accordance with a multiplication factor; a divide-by-three circuit configured to receive the second clock and output a third clock; a first divide-by-two circuit configured to receive the second clock and output a fourth clock; a second divide-by-two circuit configured to receive the fourth clock and output a fifth clock; a first multiplexer configured to receive the third clock and the fourth clock and output a seventh clock in accordance with a first selection signal; a second multiplexer configured to receive the third clock and the fifth clock and output an eighth clock in accordance with a second selection signal; and a mixer configured to receive the seventh clock and the eighth clock and output an output clock.

A method, providing an oscillator output signal to reference inputs of a PLL and an output clock circuit; providing a first divisor value to a control input of the PLL to regulate a closed loop that includes a physics cell, a receiver, and the PLL; providing a second divisor value to a control input of the output clock circuit to control an output frequency of an output clock signal; shifting the first divisor value in a first direction to cause a perturbation in the closed loop; shifting the second divisor value in an opposite second direction to counteract a response of the closed loop to the perturbation and to regulate the output frequency of the output clock signal; and based on the receiver output signal, analyzing the response of the closed loop to the perturbation.

Embodiments of the present invention synchronize multiple synthesizers, such as phase-locked loops (PLLs), in a manner that does not require communication or coordination between the synthesizers. Specifically, each synthesizer is part of a synthesizer circuit that includes a synthesizer (e.g., a PLL), a phase measurement circuit, and a synchronization circuit. A common reference signal (e.g., an alternating clock signal) is provided to the synthesizer circuits. In one exemplary embodiment, in each synthesizer circuit, the phase measurement circuit measures a phase difference between the reference signal and a corresponding output of the synthesizer, and the synchronization circuit adjusts the synthesizer operation based on the measured phase difference in such a way that all of the synthesizers operate in-phase with one another relative to the common reference signal, without having any communication or coordination between the two synthesizer circuits other than provision of the common reference signal.

A pulse signal generation circuit includes a clock frequency division component, a time delay component and a selection component. The clock frequency division component is configured to perform frequency division on a clock signal to generate a clock frequency division signal; the time delay component is configured to generate a time delay signal based on the clock frequency division signal; and the selection component is configured to receive the clock frequency division signal and the time delay signal at the same time, and select the clock frequency division signal and the time delay signal according to a preset condition to generate a pulse signal.

Systems and methods provide a fractional signal from a delta sigma modulator to a summer, a combination of an integer value and the fractional signal to a divider, and a divided clock signal from the divider in response to the combination and the input clock signal. The systems and methods also delay the divided clock signal in response to a truncation phase error and gain calibration factor from a calibration unit to provide an output clock signal having equal periods.

Clock circuits, components, systems and signal processing methods enabling digital communication are described. A phase locked loop device derives an output signal locked to a first reference clock signal in a feedback loop. A common phase detector is employed to obtain phase differences between a copy of the output signal and a second reference clock signal. The phase differences are employed in an integral phase control loop within the feedback loop to lock the phase locked loop device to the center frequency of the second reference signal. The phase differences are also employed in a proportional phase control loop within the feedback loop to reduce the effect of imperfect component operation. Cascading the integral and proportional phase control within the feedback loop enables an amount of phase error to be filtered out from the output signal.