A charge pump and a differential phase locked loop incorporating the charge pump. The charge pump includes a differential charge pump and an auxiliary charge pump. The differential charge pump has differential inputs and primary and mirror outputs. The differential charge pump is responsive to a down signal at the differential inputs to provide a negative current at the primary output and a positive current at the mirror output, and further responsive to an up signal at the differential inputs to provide a positive current at the primary output and a negative current at the mirror output. The auxiliary charge pump has differential inputs and an auxiliary output coupled to the mirror output of the differential charge pump. The differential charge pump is responsive to the down signal at the differential inputs to provide a negative current at the auxiliary output, and responsive to the up signal at the differential inputs to provide a positive current at the auxiliary output.

A communication device includes an AFE configured to track and hold a first driving signal to produce a plurality of sample signals, a shift and hold module configured to store the plurality of sample signals, and an ADC configured to respectively convert the plurality of sample signals to a plurality of digitized sample signals, the ADC including a plurality of ADC slices. A DSP is configured to calibrate the AFE based on the plurality of ADC slices corresponding to the plurality of digitized sample signals and generate an output data stream comprising the plurality of digitized samples. A skew management module is configured to detect a skew of the plurality of digitized sample signals in the output data stream generated by the DSP module, generate a programmable skew offset based on the detected skew, and correct the skew in the output data stream based on the programmable skew offset.

A type I phase locked loop (PLL) includes an oscillator and a feedback path to a phase detector. A first frequency and first relative phase of a first output signal are locked to a frequency and a phase of a first input signal. A second frequency and second relative phase of a second output signal are locked to a frequency and a phase of a second input signal. A correction to the PLL is applied to perform one of: adjusting the second relative phase to equal the first relative phase and adjusting the oscillator frequency.

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 PLL includes an input comparison circuit comparing a reference signal to a divided feedback signal to thereby control a charge pump that generates a charge pump output signal. A filter receives the charge pump output signal when a switch is closed, and produces an oscillator control signal causing an oscillator to generate an output signal. Divider circuitry divides the output signal by a divisor to produce the divided feedback signal. Divisor generation circuitry changes the divisor over time so the output signal ramps from a start frequency to an end frequency. Modification circuitry stores a first oscillator control signal equal to the value of the oscillator control signal when the frequency of the output signal is the start ramp frequency. When the frequency of the output signal reaches the end ramp frequency, the switch is opened, and the stored first oscillator control signal is applied to the loop filter.

Apparatus and methods for phase synchronization of phase-locked loops (PLLs) are provided. In certain configurations, an RF communication system includes a PLL that generates one or more output clock signals and a phase synchronization circuit that synchronizes a phase of the PLL. The phase synchronization circuit includes a sampling circuit that generates samples by sampling the one or more output clock signals based on timing of a reference clock signal. Additionally, the phase synchronization circuit includes a phase difference calculation circuit that generates a phase difference signal based on the samples and a tracking digital phase signal representing the phase of the PLL. The phase synchronization circuit further includes a phase adjustment control circuit that provides a phase adjustment to the PLL based on the phase difference signal so as to synchronize the PLL.

Disclosed are circuits and method for reducing or eliminating reference spurs in frequency synthesizers. In some implementations, a phase-locked loop (PLL) such as a Frac-N PLL of a frequency synthesizer can include a phase frequency detector (PFD) configured to receive a reference signal and a feedback signal. The PFD can be configured to generate a first signal representative of a phase difference between the reference signal and the feedback signal. The PLL can further include a compensation circuit configured to generate a compensation signal based on the first signal. The PLL can further includes a voltage-controlled oscillator (VCO) configured to generate an output signal based on the compensation signal. The compensation signal can include at least one feature for substantially eliminating one or more reference spurs associated with the PLL.

A method for filtering noise. The method may include obtaining an output signal from a phase locked loop (PLL) device. The method may include determining, using a digital phase detector and the output signal, an amount of PLL error produced by the PLL device. The method may include filtering, using a delay element and a digital filter, a portion of the amount of PLL error from the output signal to produce a filtered signal in response to determining the amount of PLL error produced by the PLL device.

A reference frequency calibration module is provided. The reference frequency calibration module includes an oscillator, a frequency divider, a phase-locked loop (PLL) and a frequency-offset calibration unit. The frequency divider couples to the oscillator. The phase-locked loop couples to the frequency divider. The frequency-offset calibration unit couples to the frequency divider and the phase-locked loop. The oscillator is configured for operatively generating an oscillating signal having an oscillating frequency. The frequency divider divides the oscillating signal having the oscillating frequency by a first division parameter to generate a first clock signal having a first reference frequency. The phase-locked loop generates a second clock signal having a second reference frequency according to the first clock signal. The frequency-offset calibration unit is configured for operatively generating the first division parameter according to the second clock signal.

The present invention is directed to data communication. More specifically, embodiments of the present invention provide a transceiver that processes an incoming data stream and generates a recovered clock signal based on the incoming data stream. The transceiver includes a voltage gain amplifier that also performs equalization and provides a driving signal to track and hold circuits that hold the incoming data stream, which is stored by shift and holder buffer circuits. Analog to digital conversion is then performed on the buffer data by a plurality of ADC circuits. Various DSP functions are then performed over the converted data. The converted data are then encoded and transmitted in a PAM format. There are other embodiments as well.