A digitally controlled voltage controlled oscillator comprising an Nbit digital to analogue convertor arranged to receive a frequency change demand signal as a digital Nbit word, and having an output provided via an integrator to a voltage controlled oscillator configured to provide a frequency output.

A hybrid numeric-analog clock synchronizer, for establishing a clock or carrier locked to a timing reference. The clock may include a framing component. The reference may have a low update rate. The synchronizer achieves high jitter rejection, low phase noise and wide frequency range. It can be integrated on chip. It may comprise a numeric time-locked loop (TLL) with an analog phase-locked loop (PLL). Moreover a high-performance number-controlled oscillator (NCO), for creating an event clock from a master clock according to a period control signal. It processes edge times rather than period values, allowing direct control of the spectrum and peak amplitude of the justification jitter. Moreover a combined clock-and-frame asynchrony detector, for measuring the phase or time offset between composite signals. It responds e.g. to event clocks and frame syncs, enabling frame locking with loop bandwidths greater than the frame rate.

Methods and systems for a digitally controlled oscillator may comprise, for example, an all-digital all digital phase locked loop (ADPLL) for generating an output clock signal from a reference clock signal, the ADPLL comprising a thermometer pulse coder comprising a plurality of frequency control word signal lines. the thermometer pulse coder may be configured to generate a frequency control word from a binary encoded frequency control word, where the frequency control word may comprise hermometer coded signals and a pulse modulated dither signal, and may select a frequency control word signal line over which to transmit the pulse modulated dither signal and may transmit the thermometer coded signals over another of frequency control word signal lines. A digitally controlled oscillator may be configured to receive a frequency control word and generate an output clock signal at a frequency determined using at least the frequency control word.

Aspects of the technology described herein relate to an ultrasound device that may has a phase-locked loop (PLL) that includes a digitally-controlled oscillator (DCO). The DCO includes a plurality of current source unit cells with respective drain switches a plurality of current source unit cells with respective source switches. The plurality of current source unit cells with respective drain switches and the plurality of current source unit cells may have different circuit topologies. Switching on one of the plurality of current source unit cells with respective drain switches may cause a voltage transition at an internal node proceeding in one voltage direction and switching on one of the plurality of current source unit cells with respective source switches may cause a voltage transition at an internal node proceeding in the opposite voltage direction.

In a phase locked loop composed of digital circuits, the circuit scale of a circuit that generates phase difference information is reduced. A multi-phase clock generation circuit generates a plurality of feedback clock signals having different phases. A feedback side frequency divider divides frequencies of the plurality of feedback clock signals and outputs the feedback clock signals as frequency-divided clock signals. A reference clock latch circuit holds the frequency-divided clock signals in synchronization with a reference clock signal and outputs a held value. A control circuit controls the frequencies of the plurality of feedback clock signals on the basis of the held value.

The present disclosure relates to systems and methods to maintain clock synchronization of multiple computers, or computer systems, through the exchange of communication messages that include clock and/or timing information.

A system includes a digital phase-locked loop (DPLL) having a loop filter and a digitally-controlled oscillator (DCO). The system also includes a clock generator coupled to an output of the DPLL, and a plurality of clock domains coupled to the clock generator. The DPLL is configured to transition between a low power mode and a normal mode, wherein the loop filter is configured to maintain its value when the DPLL transitions from the normal mode to the low power mode. The DCO is configured to output a DCO clock signal based on the maintained loop filter value when the DPLL transitions from the low power mode to the normal mode.

A digital transceiver is provided. The digital transceiver includes a clock generator configured to generate a first clock signal having a first frequency of a fixed value and a transmitter driven by the first clock signal of the first frequency to transmit data. Additionally, the digital transceiver includes an inverter coupled to the clock generator to generate an inverted first clock signal of the first frequency. Further, it includes a frequency detector configured to compare the first frequency with a second frequency of a feedback signal in a loop of feedback to determine a frequency control word F. Furthermore, it includes a digitally-controlled oscillator driven by the frequency control word F in the loop of feedback to output a second clock signal with a time-average frequency substantially synchronous to the first frequency with a boundary spread and a receiver driven by the second clock signal to receive the data.

An eye width monitor (EWM) for a clock and data recovery (CDR) circuit includes a delay circuit, a first multiplexer (MUX) and a calibration circuit. The delay circuit includes an input terminal and an output terminal. The first MUX, coupled to the delay circuit, includes a first input terminal, a second input terminal and an output terminal. The first input terminal of the first MUX is coupled to a clock input terminal of the EWM. The second input terminal of the first MUX is coupled to the output terminal of the delay circuit. The output terminal of the first MUX is coupled to the input terminal of the delay circuit. The calibration circuit, coupled to the delay circuit, is configured to receive an oscillation clock from the delay circuit and receive a reference clock, and calibrate the oscillation clock with the reference clock.

With respect to a phase locked loop (PLL) circuit that receives a first reference clock and generates an output clock, the PLL circuit includes a delay circuit that delays the first reference clock to generate a second reference clock, a feedback circuit that generates a control signal based on a phase difference between the second reference clock and a feedback clock, an oscillator that oscillates at a frequency determined based on the control signal to generate the output clock, and a divider that divides the output clock in the on state. The PLL circuit switches between a first mode and a second mode, the feedback clock in the first mode is a signal obtained by retiming an output of the divider with the output clock, and the feedback clock in the second mode is a signal obtained by retiming the first reference clock with the output clock.