Abstract: Various embodiments provide for testing a transmitter with interpolation, which can be used with a circuit for data communications, such as serializer/deserializer (SerDes) communications. In particular, some embodiments provide for data transmission test of a transmitter by: generating and outputting a pre-determined data pattern through a serializer of the transmitter; sampling a serialized data output of the serializer over a plurality of different interpolation phase positions of a phase interpolator; and using a pattern checker to error check the sampled data over the plurality of different interpolation phase positions to determine whether the data transmission test passes.

Abstract: Various embodiments provide for calibrating one or more clock signals for a serializer, which can be used with a circuit for data communications, such as serializer/deserializer (SerDes) communications. In particular, for a serializer operating based on a plurality of clock signals, some embodiments provide for calibration of one or more of the plurality of clock signals by adjusting a duty cycle of one or more clock signals, a delay of one or more clock signals, or both.

Abstract: A level shifter circuit comprises a first and second path connected in parallel. The first path comprises three inverters connected in series, and the first path generates a first intermediate clock signal based on an input clock signal. The first intermediate clock signal has a first duty cycle distortion. The second path also comprises three inverters connected in series and the second path generates a second intermediate clock signal based on the input clock signal. The second intermediate clock signal has a second duty cycle distortion. A level shifter output provides an output clock signal based on a combination of the first and second intermediate clock signals. The combination of the first and second intermediate clock signals results in an averaging of the first and second duty cycle distortions in the output clock signal.

Abstract: A physical layer (PHY) device comprises a phase interpolator to generate a set of sampler clocks. A sampler of the PHY device samples a calibration data pattern based on the set of sampler clocks. A data alignment system of the PHY device performs a coarse calibration and a fine calibration on the sampler clock signals. During the coarse calibration, the data alignment system moves the sampler clock signals earlier or later in time relative to the sampled data based on a first bit of the sampled data. During the fine calibration, the data alignment system moves the sampler clock signals earlier or later in time relative to the sampled data based on the first bit, a second bit, and a third bit in the sampled data.

Abstract: A phase interpolator of a physical layer (PHY) device comprise a phase interpolator to generate a set of asynchronous sampler clocks. A sampler of the PHY device samples a calibration data pattern using a first sampler clock from the set of asynchronous sampler clocks. A calibration control component of the PHY device detects a misalignment of a phase relationship among the set of asynchronous sampler clocks based on the sampled data. In response to detecting the misalignment, the calibration control component calibrates the first sampler clock using a second sampler clock and a third sampler clock.

Abstract: Various embodiments provide for testing a transmitter using a phase-lock loop, which can be used with a circuit for data communications, such as serializer/deserializer (SerDes) communications. In particular, some embodiments provide for data transmission test of a transmitter by: generating and outputting a pre-determined data pattern through a serializer of the transmitter; sampling a serialized data output of the serializer using a sample clock signal generated by an M/N phase-lock loop (PLL); and using a pattern checker to error check the sampled data to determine whether the data transmission test passes.

Abstract: Various embodiments provide for phase interpolators with phase adjusters to provide step resolution, which can be used with a circuit such as a data serializer/deserializer circuit. In particular, for some embodiments, a phase interpolator is coupled to a phase adjuster, where the combination of the phase interpolator and the phase adjuster is configured to interpolate between phases in phase adjustment steps at a phase adjustment step resolution. For such embodiments, the phase adjustment step resolution of the steps is achieved by controlling the phase interpolator and the phase adjuster.

Abstract: A calibration control component within a transmit (TX) or receive (RX) device executes a calibration sequence to ensure reliable data transmission and reception within the device. The calibration sequence comprises a set of calibration functions that are sequentially executed. The calibration control component detects a pause function being enabled based on a pause function configuration register. Based on detecting the pause function being enabled, the calibration control component pauses execution of the calibration sequence.

Abstract: A circuit and method for reducing intersymbol interference due to pre-cursor distortion. A first set of circuit elements located along a first circuit path of a receiver device process an analog input signal of the receiver to form an equalized representation of the input signal. A second set of circuit elements are located along a second circuit path that has lower latency than the first circuit path. The second set of circuit elements form a scaled signal as one of the following: a scaled representation of the input signal, an inverted scaled representation of the input signal, a scaled derivative of the input signal, and an inverted scaled derivative of the input signal. The scaled signal is combined with the equalized representation to cancel out a pre-cursor portion of the equalized representation.

Abstract: Systems and methods disclosed herein provide for adaptively applying pattern filters so that the edges are discarded only when the DFE feedback has adapted to levels that can corrupt the timing recovery. Embodiments of the systems and methods provide for a phase detector that selectively suppresses timing information based on the logic level states of the Qp and Qm data samples associated with the received signal.

Abstract: A phase locked loop (PLL) circuit and a method for providing a transconductance in the PLL involve forming an input voltage to an operational amplifier by a loop filter. A voltage output of the operational amplifier controls a plurality of current mirrors. A current is formed through a first one of the current mirrors as a function of the input voltage, a resistance of a resistor, and a reference voltage. The reference voltage is directly provided by, or derived from, a reference signal. A second voltage formed in the first current mirror is fed back to the operational amplifier to maintain the current through the first current mirror, which current is then mirrored into at least a second one of the current mirrors to form an output current proportional to a difference between the input voltage and the reference voltage.

Abstract: Systems disclosed herein provide for a low-noise current mirror operable under low power supply requirements. Embodiments of the systems provide for a low input current path and a high input current path, wherein the current in the low current input path sees a higher voltage and the current in the high input current path sees a lower voltage. Embodiments of the system also provide for a cascode transistor in the high input current path.

Abstract: Systems and methods disclosed herein provide for preventing the mis-equalization of signals transmitted over short transmission channels. Embodiments of the systems and methods provide for a receiver including a digital receiver equalization circuit that selectively provides a correction signal to a DFE tap weight based on the value of the current DFE tap weight as well as the logical values of the in-phase and error data samples associated with received signal.

Abstract: A circuit and method for adaptively controlling an equalizer circuit to reduce intersymbol interference at low frequencies relative to a transmit frequency of an input signal from a transmitter. The input signal is converted into a data signal by a receiver. At least one delayed data signal is formed by delaying the data signal by at least one unit interval (UI) beyond a length of a decision feedback equalizer (DFE) in the receiver. An error signal is formed by comparing the input signal to a threshold value. An error signal sample is correlated with at least one delayed data signal sample to determine whether to adjust a control coefficient of the equalizer. Thus the equalizer is controlled as if the DFE had at least one additional tap.

Abstract: A circuit and method for controlling a pre-cursor coefficient in an equalizer of a transmitter device. An input signal from the transmitter is converted into a data signal that includes data symbols transmitted in successive unit intervals. An error signal is formed by comparing the input signal to a threshold value. A determination is made whether to adjust the pre-cursor coefficient, by correlating a sample of the error signal with samples of the data signal from one unit interval earlier and two unit intervals earlier.

Abstract: A data transmitter is provided which performs digital to analog conversion, convolution with an arbitrary finite impulse response, and smoothing of the output functions without requiring a separate anti-aliasing low pass filter. To implement the data transmitter, a digital input data value is convolved with a desired impulse response. The coefficients of the desired finite impulse response filter are chosen to create a first or second derivative of an output of the data transmitter. Then, the derivative is integrated so that a resulting signal output from the data transmitter is a smooth signal which does not require further filtering.

Abstract: A method and apparatus for equalizing a communications signal transmitted through a transmission medium includes an integrated continuous-time filter and circuitry for developing a feedback signal to compensate for distortion in the signal caused by the transmission medium. The control signal adjusts the transfer characteristics of the integrated continuous-time filter thereby compensating for loss and distortion of the signal caused by the transmission medium and further tunes the integrated continuous-time filter thereby compensating for semiconductor process variations in the integrated continuous-time filter.

Abstract: A method and apparatus for reducing reference frequency signal and/or clock switching noise in self-tuned integrated continuous-time filters. In the master-slave automatic tuning scheme, one or more sample-and-hold circuits sample and hold the frequency control signal and Q-control signal generated by the feedback loop(s) of the automatic tuning system. The control signals are held at a constant level for a period of time during which the reference frequency signal and/or clock signal are quiescent. At one or more predetermined times, the frequency control and Q-control signals are intermittently updated to automatically tune the slave filter.