Abstract: One embodiment relates to a receiver circuit for a data link. The receiver circuit includes a linear equalizer for receiving an input data signal and outputting an equalized signal, and a variable gain amplifier for receiving the equalized signal and outputting an amplified signal. Adaptation circuitry is connected to the linear equalizer and the variable gain amplifier. The adaptation circuitry adapts both a gain of the variable gain amplifier and a direct current voltage setting of the linear equalizer. Other embodiments and features are also disclosed.

Abstract: A receiver circuit includes a feedback filter having multiple taps for receiving a quantized signal and outputting a feedback signal and adaptation circuitry for adapting tap weights of the feedback filter. In one embodiment, the tap weights may be adapted with variable update resolution. In another embodiment, the feedback filter may have fixed and floating taps. Other embodiments relate to methods of equalizing an input signal using a feedback filter. In one embodiment, tap weights of the feedback filter are adapted using adaptation circuitry with variable update resolution. In another embodiment, the adaptation circuitry adapts fixed and floating tap weights of the feedback filter. Other embodiments and features are also disclosed.

Abstract: Integrated circuits with high-speed communications capabilities are provided. Such types of integrated circuits may include clock data recovery (CDR) circuitry. The CDR circuitry may receive incoming data and may generate multiple clock signals that are used to latch the incoming data. The CDR circuitry may include data latching circuitry for separately latching even and odd data bits in alternating clock cycles. In particular, the data latching circuitry may be controlled using first, second, third, and fourth clock signals having different respective phase settings. The first and second clock signals may be used to capture even and odd data bits, respectively. The third and fourth clock signals may be used to sample data near the transition between the even and odd data bits. The phase of the first and second clock signals may be dynamically adjusted. The phase setting that yields the optimal link performance may be selected for normal operation.

Abstract: An integrated such as a programmable integrated circuit may include input-output pins that have associated input-output circuits. An input-output circuit may include memory interface circuits, clock recovery interface circuits, shared interpolator circuitry, and selection circuitry that may be configured to convey control signals from selected interface circuits to the shared interpolator circuitry. The interpolator circuitry may receive multiple clock signals and perform phase interpolation operations on the clock signals based on the selected control signals to produce modified clock signals. The modified clock signals may be used by the selected interface circuits for communications over the input-output pins. Logic design computing equipment such as computing equipment having CAD tools may be used to configure the selection circuitry.

Abstract: Integrated circuits having analog-to-digital converters are provided. Analog-to-digital converters may contain latched comparators. A latched comparator may include inputs configured to receive a differential input voltage signal, a differential reference voltage signal, and a clock signal. The comparator may include a preamplifier, a latching circuit, a level shifter, and a flip-flop coupled in series. The preamplifier may include large input transistors for minimizing offset, stacked tail transistors, and diode-connected load transistors for minimizing kickback noise. The preamplifier may be used to generate amplified voltage signals. The latching circuit may include a first pair of cross-coupled pull-down transistors, a second pair of cross-coupled pull-up transistors, and precharge transistors.

Abstract: Circuitry for receiving a high-speed serial data signal (e.g., having a bit rate in the range of about 10 Gpbs and higher) includes a two-stage, continuous-time, linear equalizer having only two serially connected stages. Phase detector circuitry may be provided for receiving the serial output of the equalizer and for converting successive pairs of bits in that output to successive parallel-form bit pairs. Further demultiplexing circuitry may be provided to demultiplex successive groups of the parallel-form bit pairs to final groups of parallel bits, which can be quite large in terms of number of bits (e.g., 64 parallel bits). Another aspect of the invention relates to multiplexer circuitry for efficiently going in the opposite direction from such relatively large groups of parallel data bits to a high-speed serial data output signal.

Abstract: A voltage-mode differential driver is disclosed. The differential driver includes two driver arms, each driver arm including a variable-impedance driver for driving a single-ended output signal. Each variable-impedance driver comprises multiple driver slices, where each driver slice includes a pre-driver circuit and a driver circuit. Advantageously, it has been determined that the disclosed voltage-mode driver design requires less power than conventional current-mode drivers. In one implementation, the disclosed voltage-mode driver design provides the capability of independently programming the delay of the two single-ended outputs so as to compensate for differential skew. Other embodiments and features are also disclosed.

Abstract: Systems and methods of calibrating a successive approximation register analog-to-digital converter (ADC) are disclosed. A plurality of capacitor stages, a first capacitor array, and a first capacitor stage are coupled in parallel. A capacitance of the first capacitor stage is compared to a sum of capacitances of the plurality of capacitor stages and of the first capacitor array. In response to the comparing, the capacitance of the first capacitor stage is increased by increasing the capacitance of a second capacitor array if the capacitance of the first capacitor stage is less than the sum of the capacitances of the plurality of capacitor stages and of the first capacitor array.

Abstract: Circuitry for receiving a high-speed serial data signal (e.g., having a bit rate in the range of about 10 Gpbs and higher) includes a two-stage, continuous-time, linear equalizer having only two serially connected stages. Phase detector circuitry may be provided for receiving the serial output of the equalizer and for converting successive pairs of bits in that output to successive parallel-form bit pairs. Further demultiplexing circuitry may be provided to demultiplex successive groups of the parallel-form bit pairs to final groups of parallel bits, which can be quite large in terms of number of bits (e.g., 64 parallel bits). Another aspect of the invention relates to multiplexer circuitry for efficiently going in the opposite direction from such relatively large groups of parallel data bits to a high-speed serial data output signal.

Abstract: One embodiment relates to a method of adapting a receiver for equalization of an input data signal. A variable gain amplifier (VGA) loop adapts a VGA circuit using an initial threshold voltage so as to adjust a VGA gain setting to regulate a data amplitude feeding into a decision feedback equalization (DFE) circuit. In addition, the DFE adaptation loop may adapt the DFE circuit using the initial threshold voltage. When the adaptation of the VGA is done, then the VGA gain setting is frozen and adaptation of the threshold voltage may be performed by a threshold adaptation loop. Another embodiment relates to a system which includes a DFE adaptation circuit module, a CTLE adaptation circuit module, and a threshold adaptation circuit module that adapts a threshold voltage that is fed to the DFE adaptation circuit and the CTLE adaptation circuit. Other embodiments and features are also disclosed.

Abstract: A first trimming capacitor having a first terminal and a second terminal is coupled in parallel between a first terminal and a second terminal of a first capacitor. The first trimming capacitor comprises a first plurality of switched capacitors having different capacitances coupled in parallel. Each of the switched capacitors comprises a switch capacitor and a switch coupled in series. In an illustrative application the first capacitor and the first trimming capacitor are coupled between an output terminal of an operational amplifier (op-amp) and an inverting input terminal of the op-amp. A second capacitor and a second trimming capacitor similar to the first capacitor and the first trimming capacitor are coupled between an input and the inverting input terminal of the op-amp.

Abstract: Clock alignment circuitry may include phase comparator circuitry with a first input terminal that receives as first clock signal from a first clock tree and a second input terminal that receives a second clock signal from a second clock tree. The phase comparator circuitry may compare the first and second clock signals and generate different control signals based on the first and second clock signals. The integrated circuit may further include phase interpolator circuitry that generates an output clock signal based on at least one of the control signals received from the phase comparator circuitry. Edges of the generated output clock signal may align with edges of either the first clock signal or the second clock signal.

Abstract: An integrated circuit includes a decoupling capacitor and an internal circuit. The decoupling capacitor is coupled to a first external terminal of the integrated circuit. The internal circuit in the integrated circuit is coupled to a second external terminal of the integrated circuit. The decoupling capacitor is coupled to provide supply voltage current to the internal circuit through the first and the second external terminals and through external conductors. The external conductors are outside the integrated circuit.

Abstract: A voltage-mode differential driver is disclosed. The differential driver includes two driver arms, each driver arm including a variable-impedance driver for driving a single-ended output signal. Each variable-impedance driver comprises multiple driver slices, where each driver slice includes a pre-driver circuit and a driver circuit. Advantageously, it has been determined that the disclosed voltage-mode driver design requires less power than conventional current-mode drivers. In one implementation, the disclosed voltage-mode driver design provides the capability of independently programming the delay of the two single-ended outputs so as to compensate for differential skew. Other embodiments and features are also disclosed.

Abstract: Disclosed are apparatus and methods to advantageously calibrate a transmitter output swing. One embodiment relates to a method for calibrating the output swing voltage of a transmitter. A fixed value is provided as the data input, and output swing calibration circuitry is connected to the transmitter buffer circuit. A transmitter current is set to an initial level, and the transmitter current is adjusted until the output swing of the transmitter buffer circuit is calibrated. Another embodiment relates to an integrated circuit which includes a transmitter buffer circuit, output swing calibration circuitry, and switches arranged to electrically connect the transmitter buffer circuit to the output swing calibration circuitry during an output swing calibration mode. Another embodiment relates to an output swing calibration circuit which includes comparison circuitry and logic and control circuitry.

Abstract: A circuit includes first and second bidirectional clock networks and first and second clock signal generation circuits. A first multiplexer circuit is configurable to provide a first clock signal from a first pin to the first bidirectional clock network. A second multiplexer circuit is configurable to provide the first clock signal from the first bidirectional clock network to the second bidirectional clock network. Third multiplexer circuits are configurable to provide the first clock signal from the second bidirectional clock network to the first and the second clock signal generation circuits.

Abstract: One embodiment relates to a receiver with both decision feedback equalization and on-die instrumentation. A clock data recovery loop obtains a recovered clock signal from an input signal, and a first sampler, which is triggered by the recovered clock signal, generates a recovered data signal from the input signal. A phase interpolator receives the recovered clock signal and generates a phase-interpolated clock signal. A second sampler is triggered by the recovered clock signal in a decision feedback equalization mode and by the phase-interpolated clock signal in an on-die instrumentation mode. Other embodiments and features are also disclosed.

Abstract: Systems and methods are provided for reducing jitter due to power supply noise in an integrated circuit by drawing additional current. The additional current causes the total current to generally have a frequency higher than a resonant frequency of the integrated circuit and/or a power distribution network of the integrated circuit. In one example, a power distribution network may supply power to components of an integrated circuit and data driver circuitry may draw first current to drive a data signal. Compensation circuitry may draw second current at times when the data driver circuitry is not drawing the first current, thereby causing a net of the first and second current to be higher than a resonant frequency range of the integrated circuit device and/or a component of the integrated circuit device (e.g., the power distribution network).

Abstract: Integrated circuits with phase-locked loops are provided. Phase-locked loops may include an oscillator, a phase-frequency detector, a charge pump, a loop filter, a voltage-controlled oscillator, and a programmable divider. The voltage-controlled oscillator may include multiple inductors, an oscillator circuit, and a buffer circuit. A selected one of the multiple inductors may be actively connected to the oscillator circuit. The voltage-controlled oscillators may have multiple oscillator circuits. Each oscillator circuit may be connected to a respective inductor, may include a varactor, and may be powered by a respective voltage regulator. Each oscillator circuit may be coupled to a respective input transistor pair in the buffer circuit through associated coupling capacitors. A selected one of the oscillator circuits may be turned on during normal operation by supplying a high voltage to the selected one of the oscillator circuit and by supply a ground voltage to the remaining oscillator circuits.

Abstract: Disclosed are apparatus and methods for adaptive receiver delay equalization. One embodiment relates to a method for adaptive receiver delay equalization. Filtered positive and negative polarity signals are generated by a first variable-delay filter and a second variable-delay filter, respectively. A delay difference is determined between the filtered positive and negative polarity signals, and a skew-indication signal is generated based on the delay difference. A delay control signal is generated based on the skew-indication signal, and the delay control signal is sent to at least one of the first and second variable-delay filters. Other embodiments and features are also disclosed.