A duty cycle correction circuit includes a first duty cycle detecting circuit configured to detect a duty cycle of a clock signal with a first resolution; a reference clock generating circuit configured to generate a reference clock signal by adjusting a phase of the clock signal; a second duty cycle detecting circuit configured to detect a duty cycle of the clock signal with a second resolution according to the reference clock signal and the clock signal, the second resolution being finer than the first resolution; a first duty cycle adjusting circuit configured to adjust the duty cycle of the clock signal according to one or more first control signals output from the first duty cycle detecting circuit; and a second duty cycle adjusting circuit configured to adjust the duty cycle of the clock signal according to one or more second control signals output from the second duty cycle detecting circuit.

A clock generator circuit includes: first to N.sup.th nodes, where N is an even number equal to or greater than 2; and a parallel-to-serial conversion circuit suitable for parallel-to-serial converting signals of the first to N.sup.th nodes to output a clock through an output node, wherein, in an activation section of the clock, the signals of even-numbered nodes among the first to N.sup.th nodes have a first level, and the signals of odd-numbered nodes among the first to N.sup.th nodes have a second level which is different from the first level, and wherein, in a deactivation section of the clock, the signals of the first to N.sup.th nodes have the same level.

The embodiments of the present invention provide an apparatus of an efficient digital duty cycle adjuster and the method of operation thereof. The method includes: providing an input clock having an input clock duty cycle; inserting at least one programmable delay of a programmable delay line to the input clock, the input clock has a first delay inserted for a delayed rise edge, and a second delay inserted for a delayed fall edge, wherein the first delay, the second delay, or the combination thereof, includes the programmable delay; and adjusting an output clock duty cycle of an output clock by configuring the programmable delay, the output clock is generated by a selecting circuit, the selecting circuit includes a select signal, and the select signal is determined in accordance with the first delay and the second delay.

An example pulse generation circuit includes a parallel-to-serial circuit configured to convert parallel data to serial data according to parallel clock signal and a serial clock signal, the serial data comprises a sequence of pulses; a clock generator configured to generate a clock signal; and a phase controller configured to generate the serial clock signal from the clock signal based on a phase control signal.

Described is an apparatus which comprises: a comparator to be clocked by a clock signal to be provided by a clocking circuit, wherein the clocking circuit includes: a voltage controlled delay line having two or more delay cells; a multiplexer coupled to the voltage controlled delay line and operable to configure the clocking circuit as a ring oscillator with the voltage controlled delay line forming at least one delay section of the ring oscillator; and select logic coupled to the multiplexer, the select logic is to receive a signal indicating arrival of an input clock, and is to control the multiplexer according to the indication. Described is also an apparatus which comprises: a data path to receive input data; and a clock path to receive an input clock and to provide a preconditioned clock to the data path when the input clock is absent.

Provided is a phase locked loop (PLL) that generates an output clock signal corresponding to a reference clock signal, the PLL including a first phase interpolator configured to generate a first interpolator clock signal that has a first time delay from the output clock signal and a second phase interpolator configured to generate a second interpolator clock signal that has a second time delay from the output clock signal. The PLL controls a frequency of the output clock signal based on a multiplexing the first interpolator clock signal and the second interpolator clock signal.

A fractional sampling-rate converter includes a first-in first-out (FIFO) buffer, a write logic, a read logic and a fractional interpolator. The write logic is designed to write input data samples into the FIFO at a first rate. The fractional interpolator is coupled to receive the input data samples from the FIFO and is designed to generate corresponding interpolated data samples as an output of the fractional sampling-rate converter at a second rate. The read logic is designed to cause input data samples in the FIFO buffer to be transferred to the fractional interpolator. A ratio of the second rate and the first rate is a fractional number greater than one.

A multi-tap Differential Feedforward Equalizer (DFFE) configuration with both precursor and postcursor taps is provided. The DFFE has reduced noise and/or crosstalk characteristics when compared to a Feedforward Equalizer (FFE) since DFFE uses decision outputs of slicers as inputs to a finite impulse response (FIR) unlike FFE which uses actual analog signal inputs. The digital outputs of the tentative decision slicers are multiplied with tap coefficients to reduce noise. Further, since digital outputs are used as the multiplier inputs, the multipliers effectively work as adders which are less complex to implement. The decisions at the outputs of the tentative decision slicers are tentative and are used in a FIR filter to equalize the signal; the equalized signal may be provided as input to the next stage slicers. The bit-error-rate (BER) of the final stage decisions are lower or better than the BER of the previous stage tentative decisions.

A duty cycle correction circuit includes a first duty cycle detecting circuit configured to detect a duty cycle of a clock signal with a first resolution; a reference clock generating circuit configured to generate a reference clock signal by adjusting a phase of the clock signal; a second duty cycle detecting circuit configured to detect a duty cycle of the clock signal with a second resolution according to the reference clock signal and the clock signal, the second resolution being finer than the first resolution; a first duty cycle adjusting circuit configured to adjust the duty cycle of the clock signal according to one or more first control signals output from the first duty cycle detecting circuit; and a second duty cycle adjusting circuit configured to adjust the duty cycle of the clock signal according to one or more second control signals output from the second duty cycle detecting circuit.

There is provided an interpolation circuit of an optical encoder including a phase shifter circuit, two multiplexers, two digital circuits and four comparators. The phase shifter circuit receives signals sequentially have a 90 degrees phase shift and outputs multiple phase shifted signals. Each of the two multiplexers receives a half of the multiple phase shifted signals and outputs two pairs of phase shifted signals, each pair having 180 degrees phase difference, respectively to two comparators connected thereto. Each of the two digital circuits controls the corresponding multiplexer to select the two pairs of phase shifted signals from the half of the multiple phase shifted signals.