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.

Methods and apparatus for synchronizing data transfers across clock domains for using heads-up indications. An integrated circuit includes a first-in first-out buffer (FIFO); a memory controller configured to operate in a first clock domain and coupled to the FIFO, the first clock domain associated with a first clock signal; a data fabric configured to operate in a second clock domain and coupled to the FIFO, the second clock domain associated with a second clock signal, a second frequency of the second clock signal being different from a first frequency of the first clock signal; and a controller coupled to the FIFO. In some instances, the controller determines a phase relationship between the first clock signal and the second clock signal; monitors one or more first clock edges of the first clock signal and one or more second clock edges of the second clock signal; and sends a first heads-up signal to the memory controller.

Methods and apparatus for synchronizing data transfers across clock domains for using heads-up indications. An integrated circuit includes a first-in first-out buffer (FIFO); a memory controller configured to operate in a first clock domain and coupled to the FIFO, the first clock domain associated with a first clock signal; a data fabric configured to operate in a second clock domain and coupled to the FIFO, the second clock domain associated with a second clock signal, a second frequency of the second clock signal being different from a first frequency of the first clock signal; and a controller coupled to the FIFO. In some instances, the controller determines a phase relationship between the first clock signal and the second clock signal; monitors one or more first clock edges of the first clock signal and one or more second clock edges of the second clock signal; and sends a first heads-up signal to the memory controller.

An electronic device may include wireless circuitry clocked using an electro-optical phase-locked loop (OPLL) having primary and secondary lasers. A frequency-locked loop (FLL) path and a phase-locked loop (PLL) path may couple an output of the secondary laser to its input. A photodiode may generate a photodiode signal based on the laser output. A digital-to-time converter (DTC) may generate a reference signal. The FLL path may coarsely tune the secondary laser based on the photodiode signal until the secondary laser is frequency locked. Then, the PLL path may finely tune the secondary laser based on the reference signal and the photodiode signal until the phase of the secondary laser is locked to the primary laser. The photodiode signal may be subsampled on the PLL path. This may allow the OPLL to generate optical local oscillator signals with minimal jitter and phase noise.

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.

A circuit includes a voltage-controlled oscillator (VCO) and a frequency divider. The frequency divider input is coupled to the VCO output. The circuit further includes a phase-frequency detector (PFD). A control output of the PFD is coupled to the VCO. A first PFD input is coupled to a first frequency divider output, and a second PFD input is coupled to a second frequency divider output. The first frequency divider output is configured to provide a first frequency divider signal and the second frequency divider output is configured to provide a second frequency divider signal 90 degrees out of phase with respect to the first frequency divider signal. The PFD is configured to detect an occurrence of at least two edges of a signal on the data input while the second frequency divider signal is continuously logic high across the at least two edges.

A clock recovery circuit includes a clock detector configured to receive a serial data stream from a remote device over a reverse channel, wherein the serial data stream includes clock reference data, reverse channel data, or a combination of the clock reference data and the reverse channel data, and the clock detector configured to output a clock detect signal in response to detecting the clock reference data in the serial data stream; a phase lock loop including a first detector configured to receive the serial data stream and to detect phase and frequency; and a controller configured to receive the clock detect signal and to selectively enable the first detector based on the clock detect signal.

A clock recovery circuit includes a clock detector configured to receive a serial data stream from a remote device over a reverse channel, wherein the serial data stream includes clock reference data, reverse channel data, or a combination of the clock reference data and the reverse channel data, and the clock detector configured to output a clock detect signal in response to detecting the clock reference data in the serial data stream; a phase lock loop including a first detector configured to receive the serial data stream and to detect phase and frequency; and a controller configured to receive the clock detect signal and to selectively enable the first detector based on the clock detect signal.

An accurate replica oscillator-based frequency tracking loop (FTL) is provided. The replica oscillator used in the FTL can be at a lower frequency and therefore can consume much lower power compared to a main oscillator, such as an injection locked oscillator (ILO). The proposed FTL accurately sets the free running frequency of an ILO across process, voltage and temperature (PVT). Techniques are also provided to compensate the gain and offset error between the replica oscillator and the ILO.

A phase-locked loop circuit includes a voltage controlled oscillator (VCO) that generates a VCO clock in response to a voltage control signal, a divider that divides the VCO clock to output a division clock, a phase-frequency error detector that receives a reference clock and outputs a first error compensation signal, a sampler that receives the reference clock and oversamples the reference clock at a rising edge or a falling edge to output a sampling clock, a window phase error detector that receives the reference clock and outputs a second error compensation signal, a residue phase error detector that outputs a third error compensation signal, an adder that accumulates the first error compensation signal, the second error compensation signal, and the third error compensation signal to output a final error compensation signal, and a loop filter that converts and output the final error compensation signal into the voltage control signal.