A phase-locked loop (PLL) performs hitless switching from a first reference clock (ref1) to a second reference clock (ref2) by entering holdover mode (418), and aligning the feedback clock (fbclk) to the second reference clock while in holdover mode. The alignment is performed by adjusting a divisor input (D) for the multi-mode divider (128) that divides the output clock frequency (PLLout) to generate the feedback clock. Other features are also provided.

A phase-locked loop (PLL) performs hitless switching from a first reference clock (ref1) to a second reference clock (ref2) by entering holdover mode (418), and aligning the feedback clock (fbclk) to the second reference clock while in holdover mode. The alignment is performed by adjusting a divisor input (D) for the multi-mode divider (128) that divides the output clock frequency (PLLout) to generate the feedback clock. Other features are also provided.

A clock and data recovery circuit is disclosed. The clock and data recovery circuit includes a phase detection circuit, a first voting circuit, a low-pass filtering circuit and a phase interpolation circuit. The phase detection circuit is configured to receive a first signal and a clock signal and generate a phase signal. The first voting circuit is configured to charge at least one capacitance component according to the phase signal and generate a first voting signal according to a charging result. The low-pass filtering circuit is configured to generate a phase control signal according to the first voting signal. The phase interpolation circuit is configured to generate the clock signal according to the phase control signal.

A clock and data recovery circuit is disclosed. The clock and data recovery circuit includes a phase detection circuit, a first voting circuit, a low-pass filtering circuit and a phase interpolation circuit. The phase detection circuit is configured to receive a first signal and a clock signal and generate a phase signal. The first voting circuit is configured to charge at least one capacitance component according to the phase signal and generate a first voting signal according to a charging result. The low-pass filtering circuit is configured to generate a phase control signal according to the first voting signal. The phase interpolation circuit is configured to generate the clock signal according to the phase control signal.

A chirp linearity detector, integrated circuit, and method are provided. The chirp linearity detector comprises a phase-locked loop (PLL) frequency sampling circuit and a frequency sweep linearity measuring circuit. The PLL frequency sampling circuit comprises a frequency divider circuit for receiving a PLL output signal from a PLL and for providing a frequency divided output signal, a first low pass filter circuit for receiving the frequency divided output signal, for reducing harmonic mixing, and for providing a mixer input signal, a mixer circuit for receiving the mixer input signal, for mixing the mixer input signal with a local oscillator signal, and for providing a mixer output signal, a second low pass filter circuit for performing anti-aliasing filtering and for providing an analog-to-digital converter (ADC) input signal, and an ADC circuit for digitizing the ADC input signal and for providing a digital output signal.

An all-digital phase locked loop (ADPLL) is provided. The ADPLL comprises a pattern generator adapted to generate a frequency control word (FCW) based on a predefined setting and a system clock. In addition, the ADPLL comprises a phase accumulator adapted to translate the FCW into a phase trajectory. The ADPLL further comprises a phase comparator adapted to generate a phase error signal representing a difference between the phase trajectory and the phase of an output oscillation frequency. Moreover, the ADPLL comprises a controller adapted to control a phase of the output oscillation frequency with respect to the phase trajectory.

Apparatus and methods for timing offset compensation of frequency synthesizers are provided herein. In certain embodiments, an electronic system includes a frequency synthesizer, such as a fractional-N phase-locked loop (PLL), which generates an output clock signal based on timing of a reference clock signal. Additionally, the electronic system includes an integer PLL configured to compensate for a timing offset, such as a phase offset and/or frequency offset, of the frequency synthesizer based on timing of the output clock signal.

A quantizer generates a thermometer coded signal from an analog voltage signal. Data weighted averaging (DWA) of the thermometer coded signal is accomplished by controlling the operation of a crossbar switch controlled by a switch control signal to generate an output DWA signal. The output DWA signal is latched to generate a latched output DWA signal which is processed along with bits of the thermometer coded input signal in feedback loop to generate the switch control signal. The latching of the output DWA signal is performed in an input register of a digital-to-analog converter which operates to convert the latched output DWA signal to a feedback analog voltage from which the analog voltage signal is generated. The switch control signal specifies a bit location for a beginning logic transition of the output DWA signal cycle based on detection of an ending logic transition of the latched DWA signal.

A phase-locked loop is disclosed. The phase-locked loop includes a phase error detector, an event detector, a loop filter, and an oscillator. The phase error detector is configured to receive an input signal and a feedback signal and output a phase error signal. The event detector is configured to detect a loss of lock condition based on the phase error signal. The loop filter is configured to filter the phase error signal to generate a filtered control signal based on a first set of filter parameter values, and in response to the loss of lock condition, filter the phase error signal to generate the filtered control signal based on a second set of filter parameter values different from the first set of filter parameter values. The oscillator is configured to output an output signal having a phase that is based on the filtered control signal.

A phase-locked loop circuit calibration method for a memory storage device including a rewritable non-volatile memory module is provided according to an exemplary embodiment of the disclosure. The method includes: receiving a first signal from a host system; generating a jitter signal by the memory storage device; generating a second signal according to the first signal and the jitter signal; performing a phase-lock operation on the second signal to generate a third signal by a phase-locked loop circuit; and calibrating an electrical parameter of the phase-locked loop circuit according to a variation of a time difference between the first signal and the third signal.