Serial data transfer uses ever increasing transmission rates. The data transfer rate of a clock-and-data recovery (CDR) deserializer can be increased by using multiple independent sampler blocks that process serial input data in parallel. For this purpose, the clock output signals from the various independent blocks are first mutually aligned in proper order using a lower speed clock, and subsequently offset from one another such that sampling instances of the various sampler blocks are interleaved. Digitized data words corresponding to common input data and outputted by the various sampler blocks are compared after alignment of the clock output signals to correct additional timing misalignment between the multiple sampler blocks. The digitized data words need only be aligned once or at most infrequently after the clock output signals are aligned, since the additional timing misalignment is caused mainly path delays that are substantially invariant over time.

A phase interpolator includes a control circuit configured to generate a selection control signal that corresponds to a selected coarse phase interval, and generate a weight setting signal for generating a phase interpolation clock signal with an interpolated phase within the coarse phase interval; a phase selector configured to receive a plurality of inversion delay clock signal pairs, select at least two inversion delay clock signal pairs from the plurality of inversion delay clock signal pairs based on the selection control signal, select and output a selection delay clock signal pair corresponding to the coarse phase interval from the selected at least two inversion delay clock signal pairs; and a phase mixer configured to receive the selection delay clock signal pair from the phase selector and generate the phase interpolation clock signal based on the weight setting signal.

A circuit for performing clock recovery according to a received digital signal. The circuit includes at least an edge sampler and a data sampler for sampling the digital signal, and a clock signal supply circuit. The clock signal supply circuit provides edge clock and data clock signals offset in phase from one another to the respective clock inputs of the edge sampler and the data sampler. A digital phase detector determines if the data clock is early, late or synchronized with respect to data value transitions in the digital signal, and based on that determination provides a phase adjustment signal to the clock signal supply circuit, which is operable to vary phases of the data and edge clock signals accordingly.

A serial transmitter that outputs one symbol every unit interval (UI) from a data source is presented. The serial transmitter includes a serial output port that outputs one symbol every unit interval (UI) from a data source. The serial transmitter also includes a plurality of driver segments that jointly drive the serial output port. Each driver segment is configured to use one of N phases of a sampling clock to serialize and transmit data from the data source. Different sets of the driver segments are configured to use different phases of the sampling clock for serializing and transmitting data, the sampling clock being a half-rate clock having a period of two UI.

A clock and data recovery (CDR) circuit includes a phase detector, a frequency accumulator, and a sequencer circuit. The phase detector generates a phase detect result signal in response to phase detection of a plurality of samples, which are generated by sampling a first data signal from a receiver using a sampling clock. The frequency accumulator accumulates, using a frequency register, frequency offset information from the phase detect result signal to generate an accumulated total. The frequency offset information is associated with a frequency difference between a first reference clock of the receiver and a second reference clock associated with the first data signal. The accumulated total is stored in the frequency register and provided from the frequency register for updating the sampling clock. The sequencer circuit is configured to perform a reset operation to reset the accumulated total in the frequency register based on a sequence of sequence elements.

A circuit for demodulating an input signal is described. The circuit may be configured to demodulate signals modulated with amplitude-based modulation schemes, such as amplitude shift keying (ASK). The demodulator may comprise a clock extractor configured to generate a clock signal in response to receiving an amplitude-modulated input signal, a phase shifter configured to generate a sampling signal by phase-shifting the clock signal by approximately /2, and a sampler configured to sample the input signal in correspondence to one or more edges (such as one or more falling edges) of the sampling signal. In this way, the amplitude-modulated input signal may be sampled at its peak, or at least near its peak, thus ensuring high signal fidelity.

A phase interpolator includes a control circuit configured to generate a selection control signal that corresponds to a selected coarse phase interval, and generate a weight setting signal for generating a phase interpolation clock signal with an interpolated phase within the coarse phase interval; a phase selector configured to receive a plurality of inversion delay clock signal pairs, select at least two inversion delay clock signal pairs from the plurality of inversion delay clock signal pairs based on the selection control signal, select and output a selection delay clock signal pair corresponding to the coarse phase interval from the selected at least two inversion delay clock signal pairs; and a phase mixer configured to receive the selection delay clock signal pair from the phase selector and generate the phase interpolation clock signal based on the weight setting signal.

Apparatus and methods are provide for frame synchronization and clock and data recovery. In an example, a method can include receiving initial data of a stream of information, sampling the stream of information a plurality of times per unit interval to provide a plurality of sample intervals, integrating transition information for each sample interval, and selecting a sampling phase to sample each symbol of the stream of data using the integrated transition information.

A clock recovery circuit includes: a multi-phase clock generating circuit configured to generate multi-phase clocks having different phases; a plurality of switch elements configured to control coupling between each of the multi-phase clocks and an output node; and a switch control circuit configured to compare phases of the multi-phase clocks and input data and control, to an on-state, at least two switch elements of the plurality of switch elements corresponding to at least two clocks whose phase difference falls within a given range, wherein the at least two clocks selected through the at least two switch elements controlled to the on-state are subjected to phase interpolation to recover an output clock.

A clock recovery circuit includes a delay line circuit configured to output a plurality of first clocks having different phases obtained by delaying an input data signal, a register circuit configured to determine and write received data in the input data signal based on the first clocks, and a control circuit configured to control the writing of the data in the register circuit based on transitions of the input data signal.