A multi-phase clock circuit includes a first delay circuit, a second delay circuit, a third delay circuit, a first clock mixer circuit, and a second clock mixer circuit. The first, second, and third delay circuits are coupled in series. The first clock mixer circuit includes a first input and a second input. The first input is coupled to an output of the first delay circuit. The second input is coupled to an output of the second delay circuit. The second clock mixer circuit also includes a first input and a second input. The first input of the second clock mixer circuit is coupled to an output of the second delay circuit. The second input of the second clock mixer circuit is coupled to an output of the third delay circuit.

A method and apparatus of generating precision phase skews is disclosed. In some embodiments, a phase skew generator includes: a charge pump having a first mode of operation and a second mode of operation, wherein the first mode of operation provides a first current path during a first time period, and the second mode of operation provides a second current path during a second time period following the first time period; a sample and hold circuit, coupled to a capacitor, and configured to sample a voltage level of the capacitor at predetermined times and provide an output voltage during a third time period following the second time period; and a voltage controlled delay line, coupled to the sample and hold circuit, and having M delay line stages each configured to output a signal having a phase skew offset with respect to preceding or succeeding signal.

A sub-ranging time-to-digital converter (TDC) is disclosed that includes two ring oscillators for determining a time difference between two clock edges.

A locked loop circuit is disclosed. The locked loop circuit includes phase detection circuitry to generate a first error output based on a phase difference between a first reference input and a locked-loop output. Summing circuitry receives the first error output and a second error signal. The second error signal is based on one from a selection of error values. Oscillator/delay circuitry generates the locked-loop output. For a first mode of operation, the second error signal is based on a first selected error value. For a second mode of operation, the second error signal is based on a second selected error value different than the first selected error value.

Methods and systems are described for receiving N phases of a local clock signal and M phases of a reference signal, wherein M is an integer greater than or equal to 1 and N is an integer greater than or equal to 2, generating a plurality of partial phase error signals, each partial phase error signal formed at least in part by comparing (i) a respective phase of the M phases of the reference signal to (ii) a respective phase of the N phases of the local clock signal, and generating a composite phase error signal by summing the plurality of partial phase error signals, and responsively adjusting a fixed phase of a local oscillator using the composite phase error signal.

A subranging time-to-digital converter (TDC) is disclosed that includes two ring oscillators for determining a time difference between two clock edges.

A frequency multiplier comprises a phase generator configured to receive an oscillation signal and to provide at phase generator outputs versions of the oscillation signal, which are phase-shifted with respect to each other. An injection-locked ring oscillator comprises a plurality of stages, wherein each of the phase generator outputs is coupled to a different stage of the plurality of stages for multi-point injection. A combiner combines output signals of the plurality of stages of the injection-locked ring oscillator into a signal having a frequency which is a multiple of a frequency of the oscillation signal.

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.

A circuit and corresponding method control cycle time of an output clock used to clock at least one other circuit. The circuit comprises an agile ring oscillator (ARO) and ARO controller. The ARO includes at least one instance of a first ring oscillator (RO) and second RO that generate high and low phases, respectively, of cycles of the output clock. The ARO controller controls durations of the high and low phases, independently, via first and second control words output to the ARO, respectively. In a present cycle of the output clock, the ARO controller effects a change to the high or low phase, or a combination thereof, in a next cycle of the output clock by updating the first or second control word, or a combination thereof, based on an indication of expected usage of the at least one other circuit in the next cycle. The change improves a performance-to-power ratio of the at least one other circuit.

Methods and systems are described for receiving N phases of a local clock signal and M phases of a reference signal, wherein M is an integer greater than or equal to 1 and N is an integer greater than or equal to 2, generating a plurality of partial phase error signals, each partial phase error signal formed at least in part by comparing (i) a respective phase of the M phases of the reference signal to (ii) a respective phase of the N phases of the local clock signal, and generating a composite phase error signal by summing the plurality of partial phase error signals, and responsively adjusting a fixed phase of a local oscillator using the composite phase error signal.