Abstract: A data bus inversion (DBI) circuit includes at least one DBI block configured to invert an input data signal based on the logic state of input data bits. The DBI block includes a comparison deciding unit configured to generate, in a first mode, a comparison signal based on the number of changed bits by comparing respective bit signals of the input data signal and a previous input data signal. The comparison deciding unit generates an inversion control signal which controls whether the input data will be inverted or not. In a second mode, the comparison deciding unit generates an inversion control signal based on the predominant logic state of the input data signal bits. A data converting unit is configured to invert the input data signal in response to the inversion control signal. Method embodiments are also disclosed.

Abstract: A bi-directional universal serial bus (“USB”) circuit for boosting a signal on a USB bus disclosed. The circuit includes a first stage inverting buffer coupled to a second stage inverting buffer to form a non-inverting buffer circuit. A high pass filter is coupled in series with the non-inverting buffer circuit to provide AC coupling to the USB bus and to allow fast signal edges through the circuit. The booster circuit is arranged to improve signal quality over a USB bus to allow additional USB devices and longer USB busses to be utilized.

Abstract: A signal transmission circuit is formed by a transmitter, a receiver, a transmission line therebetween, and a bias circuit. The transmitter receives an input signal to transmit a signal corresponding to the input signal to the input of the transmission line. A voltage amplitude of the transmitted signal is smaller than a voltage amplitude defined by first and second power supply terminals. The receiver receives the transmitted signal, adjusts a voltage of the received signal in accordance with a bias voltage to generate a voltage adjusted signal, and wave-shapes the voltage adjusted signal to generate an output signal. The bias circuit differentially amplifies the output signal of the receiver and an inverted signal thereof to generate the bias voltage. The bias circuit includes a capacitor charged and discharged in accordance with the bias voltage.

Abstract: A first clock signal of frequency F is used to couple data to an off-chip driver (OCD) using a master/slave flip flop (FF), wherein the master latch is clocked with the first clock signal and the slave latch is clocked with the complement of the first clock signal. A second clock signal of frequency F/2 is generated from the first clock signal. The second clock signal is shifted a time equal to substantially one-half the cycle of the first clock signal. In one embodiment, the second clock is shifted using a delay line circuit. In another embodiment, the second clock is shifted using a master/slave FF, wherein the master latch is clocked with the complement of the first clock signal and the slave latch is clocked with the first clock signal. The logic state transitions of the data between edges of the propagating clock thereby reducing coupling to the clock transitions and thus reducing edge jitter.

Abstract: A leakage efficient anti-glitch filter. In accordance with a first embodiment of the present invention, a leakage efficient anti-glitch filter with variable delay stages comprises a plurality of variable delay stages and a coincidence detector element for detecting coincidence of an input signal to the delay element and an output of the delay element. The plurality of variable delay stages may comprise stacked inverter circuits or stacked NAND circuits.

Abstract: An inverter with adjustable threshold and irrelative to voltage, temperature, and process is disclosed. The inverter includes an input end for receiving an input signal; an output end for outputting an inverted signal of the input signal; a first PMOS whose gate is coupled to the input end, drain is coupled to the output end, and the source is coupled to a power supply; a first NMOS whose gate is coupled to the input end, drain is coupled to the output end, and source is coupled to a ground end, and an adjustable current source coupled to the output end for providing current with adjustable size to the output end for adjusting threshold of the inverter.

Abstract: The programmable slew rate driver uses separate and programmably selectable resistors for time constants for on and off transitions on the NMOS and PMOS output transistors. By proper setting of gate voltage time constants and overlap of NMOS and PMOS “on” times, a desired output slew rate is accomplished, having a smooth output transition, without generation of shoot-through current. The programmable slew rate driver includes a first driver transistor coupled between the first supply voltage and output, a second driver transistor coupled between the second supply voltage and output, a plurality of upper transition blocks coupled in parallel and a plurality of lower transition blocks coupled in parallel between the first and second supply voltage. The rates of change and overlap of the gate voltages are in turn substantially determined by the resistance of the lower transition control blocks and the capacitance of the gate of the second driver transistor.

Abstract: Methods of compensating for power supply variations in an integrated circuit. During operation of the IC die, a power supply voltage level is monitored. When the power supply voltage level drops below a specified level, a performance compensation circuit in the IC is enabled, bringing a first delay (e.g., the rising delay) for a compensated circuit in the IC more closely into alignment with a second delay (e.g., a falling delay) for the circuit. When the power supply voltage level exceeds the specified level, the performance compensation circuit is disabled. When the IC is a programmable IC, for example, the compensated circuit can be a programmable interconnect multiplexer of the programmable IC. In these embodiments, the power supply voltage level for the pass transistors in the interconnect multiplexer can be monitored and compensated for as described above.

Abstract: Multiplexer circuits that can be programmed to selectively balance the rising and falling delays through the circuits in the presence of process variations and/or variations in power levels. These multiplexer circuits can be used, for example, as programmable interconnect multiplexers in the interconnect structures of programmable logic devices (PLDs). A multiplexer circuit includes a multiplexer (e.g., driven by a plurality of interconnect lines in a PLD), a logic gate (e.g., an inverter) driven by the multiplexer, and a performance compensation circuit. The performance compensation circuit is coupled to the output terminal of the inverter, and has a compensation enable input terminal. The performance compensation circuit is coupled to adjust a trip point of the logic gate based on a value of a signal provided on the compensation enable input terminal.

Abstract: Methods of compensating for process variations in an integrated circuit. Multiplexer circuits can be programmed to balance the rising and falling delays through the circuits in the presence of process variations. These multiplexer circuits can be used, for example, as programmable interconnect multiplexers in the interconnect structures of PLDs. During wafer sort or final test, a process corner can be determined for each die. One or more E-fuses can be set to predetermined level(s) to program the process corner information into the die, or the values can be stored in some other type of non-volatile memory. The stored values are utilized by the programmable multiplexer circuits to optionally adjust the rising and/or falling delays through the multiplexer circuits to achieve a balance between the rising and falling delays.

Abstract: A logic device with low electromagnetic interference. The logic device includes a digital logic gate, a voltage-limited circuit and a current-limited circuit. The digital logic gate provides a corresponding digital logic function. The voltage-limited circuit is connected to the digital logic gate in order to provide a fixed voltage to the digital logic gate to thus reduce an output voltage swing of the digital logic gate. The current-limited circuit is connected to the digital logic gate in order to provide a fixed current to the digital logic gate to thus reduce a transient current of the digital logic gate. Accordingly, an electromagnetic interface (EMI) caused by switching of the digital logic gate is reduced with the reduced output voltage swing and transient current.

Abstract: The invention relates to a method and a device for transmission with reduced crosstalk in interconnections used for sending a plurality of signals, such as the interconnections made with flat multiconductor cables, or with the tracks of a printed circuit board, or inside an integrated circuit. An interconnection with four parallel transmission conductors plus a reference conductor has each of its ends connected to a termination circuit. The transmitting circuit receives at its input the signals of the four channels of the source and its output terminals are connected to the conductors of the interconnection. The receiving circuit's input terminals are connected to the conductors of the interconnection, and its four output channels are connected to the destination. The signals of the four channels of the source are sent to the four channels of the destination, without noticeable crosstalk.

Abstract: A common-mode shifting circuit for shifting the common-mode output voltage of a CML device to an arbitrary voltage is disclosed. A constant current source is provided at each output of the CML device. The constant current may be a positive or negative current, tending to raise or lower the common-mode output voltage, respectively. The constant current sources are preferably connected to an alternate voltage supply having a higher voltage than that the supply for the CML device. The invention further provides a method for adjusting the output signal of a current-mode logic circuit having two or more output ports, comprising the step of providing a constant current at each output port of the current-mode logic circuit, whereby the common-mode voltage at the output ports of said current-mode logic circuit is level-shifted.

Abstract: Apparatus and method for counteracting high frequency attenuation of a differential input data signal as the signal is conducted through a data link. A differential input data signal is transmitted from a transmitter to a receiver through a data link. The data eye of the differential input data signal is modified at the transmitter in response to feedback from the receiver where the extent of the data eye of the differential input data signal, after being conducted through the data link, is determined. The feedback to the transmitter, dependent on the determination of the extent of the data eye, controls the data eye at the transmitter and the equalization of the differential input data signal by adapting the differential input data signal to anticipate high frequency attenuation of the differential input data signal in the data link.

Abstract: A skew correction system incorporated into a transmitter forwarding a differential signal on a differential lane monitors returning signal reflections when the receiving end of the differential lane is appropriately terminated. Based on an analysis of the reflections, the skew correction system adjusts the relative timing of complementary edges of the differential signal departing the transmitter so as to substantially eliminate skew at the receiving end of the differential lane.

Abstract: A signaling circuit having reduced parasitic capacitance. The signaling circuit includes a plurality of driver circuits each having an output coupled to a first output node, and a plurality of select circuits each having an output coupled to a control input of a corresponding one of the driver circuits. Each of the select circuits includes a control input to receive a respective select signal and a plurality of data inputs to receive a plurality of data signals. Each of the select circuits is adapted to select, according to the respective select signal, one of the plurality of data signals to be output to the control input of the corresponding one of the driver circuits.

Abstract: A differential receiver includes a feedback circuit connected between an output node and one common node of the differential receiver to reduce the bandwidth and reject noise for a specific interval of time. In operation, a differential receiver bias current is controlled responsive to an output signal at the output node. Bias current is turned on during a steady-state mode with respect to the output signal, and is turned off, for a given delay period, in response to a transition mode with respect to the output signal.

Abstract: Disclosed is an output buffer including a first output buffer for data for receiving a data signal and outputting an output signal from an output terminal, a second output buffer with an output end thereof connected to the output terminal, and a selection circuit. The selection circuit receives a control signal indicating whether de-emphasis enabled or de-emphasis is disabled and performs switching control so that when the control signal indicates that the de-emphasis is disabled, the second output buffer is deactivated, when the control signal indicates that the de-emphasis is enabled, emphasis data obtained on delaying the data signal through a delay circuit is supplied to an input end of the second output buffer, thereby causing the second output buffer to operate as a de-emphasis buffer, and when a test control signal is of a value indicating an amplitude margin test, the data signal is selected to be supplied to the input end of the second output buffer.

Abstract: An impedance control system is composed of a target circuit having a controllable impedance; a replica circuit having a structure identical to the target circuit; a first binary counter providing the replica circuit with a first impedance control code indicative of a counter value of the first binary counter for controlling an impedance of the replica circuit; a comparator comparing a voltage received from the replica circuit with a reference signal; a second binary counter responsive to an output signal from the comparator for being counted up or down; and a control circuit extracting upper multiple bits out of a counter value of the second binary counter, and generating a second impedance control code indicative of the upper multiple bits. The impedance of the target circuit is controlled in response to the second impedance control code.

Abstract: A method and apparatus for ameliorating the effects of noise generated by a bus interface provides improved performance of integrated circuits having other circuits sensitive to the transient noise introduced by bus signal switching. Additional signals are generated that equalize the frequency of occurrences of the transients, so that an effectively constant and non-data-dependent frequency is generated over the totality of the signals. The loading characteristics of the additional signals and interface signals are matched, and the interface and additional signals may be generated as complementary pairs, so that the net DC energy of the transients is also substantially made equal to zero. Any or all of the interface and additional signals may be used as data signals, or all but one of the signals may be supplied to an internal or external dummy load. A loading circuit may be calibrated by a circuit that senses the interface loading.

Abstract: A control circuit including a first control unit, controlling a logic circuit, connected between a power supply and a virtual ground, the control unit connecting the virtual ground to a ground in response to a mode control signal when the logic circuit operates in an active mode and disconnecting the virtual ground from the ground in response to the mode control signal when the logic circuit operates in a sleep mode. A method of controlling including connecting the logic circuit between a power supply and a virtual ground, connecting the virtual ground to a ground in response to a mode control signal when the logic circuit operates in an active mode, and disconnecting the virtual ground from the ground in response to the mode control signal when the logic circuit operates in a sleep mode.

Abstract: A noise canceller circuit capable of suppressing power supply noise, produced by transition of a data signal, even in case a data signal is increased in speed. The noise canceller circuit includes an output buffer 20 for outputting a first binary signal that may undergo transition at a timing synchronized with clock signals, and a second output buffer 21 for outputting a second binary signal which has undergone transition in case the first binary signal does not undergo transition at the above timing and for outputting the second binary signal without transition in case the first binary signal has undergone transition at the above timing. The respective output circuits of the output buffers 20, 21 are the same and are constructed so that the respective power supply sources VDD and the ground GND are common to the buffer circuits. A capacitor 24 for absorbing the noise is provided across the power supply and the ground.

Abstract: A leakage efficient anti-glitch filter with variable delay stages. In accordance with a first embodiment of the present invention, a leakage efficient anti-glitch filter with variable delay stages comprises a plurality of variable delay stages and a coincidence detector element for detecting coincidence of an input signal to the delay element and an output of the delay element. The plurality of variable delay stages may comprise stacked inverter circuits or stacked NAND circuits.

Abstract: A receiver circuit arrangement includes a receiver circuit an input for receiving an input signal an output for outputting an output signal and an inverter circuit with switching transistors. The input signal is fed to the receiver circuit. At least one control transistor is connected in series with the switching transistors. A control circuit is connected on the input side to a terminal for a reference voltage and on the output side to the control terminal of the control transistor of the inverter circuit. The control circuit is designed such that the control transistor is driven by the regulating switching circuit in the event of deviations of the reference voltage from a voltage value in a reference operating state with a control voltage that deviates with respect to the reference operating state.

Abstract: The present invention is directed to bidirectional buffer with slew rate control in at least one direction. The present invention is also directed to a method of bidirectionally transmitting signals with slew rate control in at least one direction.

Abstract: A data acceleration device may include a pull-up driver for driving a pull-up in response to the signal level on a first node, a pull-down driver for driving a pull-down in response to the signal level on the first node, a first pull-up circuit for pull-up driving a second node which is electrically coupled with the first node, in response to an output signal from the pull-up driver, a first pull-down circuit for pull-down driving the second node, in response to an output signal from the pull-down driver, a delay circuit for delaying a signal from the second node by a preset time to output a delayed signal, a first switch for switching an operation of the first pull-up circuit in response to an output signal from the delay circuit, and a second switch for switching an operation of the first pull-down circuit in response to the output signal from the delay circuit. Also, there is presented a data transmission apparatus including the data acceleration device.

Abstract: Configurable communications modules and methods of making the same are described. In one aspect, a communications module includes a data channel and a termination impedance controller. The data channel is operable to translate data signals in at least one direction between a transmission cable interface and a host device interface. The data channel has a variably configurable termination impedance at a host device node that is connectable to a host device. The termination impedance controller is operable to set the variably configurable termination impedance of the data channel to match the termination impedance to the host system.

Abstract: Various circuit embodiments comprise an input node to receive an input signal for a CMOS transistor stack, a first output node to deliver the input signal to a PMOS pull-up transistor of the CMOS transistor stack, and a second output node to deliver the input signal to an NMOS pull-down transistor of the CMOS transistor stack. A first passive signal path between the input node and the first output node is adapted to pass an effective rising edge of the input signal and delay an effective falling edge of the input signal to a gate of the PMOS transistor. A second passive signal path between the input node and the second output node is adapted to delay the effective rising edge of the input signal and pass the effective falling edge of the input signal to a gate of the NMOS transistor. Other aspects and embodiments are provided herein.

Abstract: An integrated circuit (IC) includes mechanisms for adjusting or setting the gate bias of one gate of one or more multi-gate transistors. The IC includes a gate bias generator. The gate bias generator is configured to set a gate bias of one gate of the one or more multi-gate transistors within the IC. More specifically, the gate bias generator sets the gate bias of the transistor(s) so as to trade off performance and power consumption of the transistor(s).

Abstract: Programmable logic device integrated circuitry having differential I/O circuitry is provided. The differential I/O circuitry may include output drivers for providing differential digital output data signals across pairs of output lines. A user may program the I/O circuitry to accommodate different high-speed differential I/O signaling standards. The user may also program the I/O circuitry to provide a desired amount of preemphasis to the output data signals.

Abstract: Circuitry and methods are provided for an LVDS-like transmitter that may be able to DC couple to a receiver having a CML termination scheme. Replacing the common mode voltage source of an LVDS transmitter with a resistive pulldown to ground may allow the transmitter to interface in a DC coupled fashion with a CML receiver. Further, the resistive pulldown may be programmable. This LVDS-like transmitter may be able to support a wider customer base by allowing it to DC couple to a wider range of termination voltage levels, such as CML termination voltage levels.

Abstract: A method, apparatus and machine-readable medium for improving communication between logic elements in an integrated circuit (IC) is provided. This is achieved by using a point-to-point approach for IC placement and routing, to address the increase in complexity in terms of design size and/or Deep Sub-Micron physical effects. The method involves providing a separate conductor member between an output of a logic element and each of one or more logic elements for interconnecting the one or more logic elements with the logic element. The method further involves providing a separate buffer between the output of the logic element and each of the one or more logic elements for interconnecting the one or more logic elements with the logic element. Furthermore, the method involves interconnecting the output of the logic element and the one or more logic elements, using the provided separate conductor member, and the provided separate buffer.

Abstract: A tunable impedance circuit is provided wherein at least one of a plurality of impedance elements is combined with at least another of the plurality of impedance elements to produce a composite impedance. A control voltage is used to determine how many of the impedance elements are to be combined to produce the composite impedance. A current that is substantially invariant over a range of operating conditions is caused to flow through a control impedance to produce the control voltage.

Abstract: A programmable logic device having logic block that can be selectively placed in a reduced power consumption mode is provided. The PLD includes a plurality of logic array blocks (LABs) and a plurality of interconnects defining signal pathways between the plurality of LABs. Sleep control logic of the PLD issues a sleep control signal for placing at least a portion of the plurality of LABs in a sleep mode. Bias control logic of the PLD is in communication with the sleep control logic. The bias control logic is triggered by the sleep control signal to issue a first bias control signal and a second bias control signal. The first and second bias control signals are transmitted to corresponding transistors of the LABS. The first and second bias control signals apply a reverse bias to corresponding transistor wells to increase threshold voltages for the respective transistors.

Abstract: A purpose of a high-speed signal transmission system of the present invention is to pass a high-speed digital signal through an outside-chip line exchanging a signal with a high speed LSI chip with a band higher than GHz. The high-speed signal transmission system of the present invention has a configuration of: insertion of a circuit for feeding back received information and adjusting a waveform at a sending side based on genetic algorithm; a device structure for automatically performing pump up and pump down of a transistor carrier; a transmission line of a wiring out of a transistor; and elimination of a common power source of a circuit.

Abstract: There is provided an output driver for use in a semiconductor device capable of remarkably improving linearity of impedance by reducing or minimizing a change of an impedance for output data caused due to a change of an external power supply. The output driver for outputting internal data of a semiconductor device to the exterior of a chip comprises a first driving section including a driving transistor to maintain an impedance for applied data at a certain level in response to the data; and a second driving section for compensating for linearity of the impedance in response to an operation signal from the driving transistor of the first driving section and providing an output terminal with the data.

Abstract: A slew rate calibrating circuit and a slew rate calibrating method are provided which are capable of adjusting, with high accuracy, a slew rate of a signal to be output to a transmission path. A first clock is input and a delay time of a variable delay circuit is increased or decreased so that a phase of the first clock coincides with a phase of a first differential buffer output signal which rises when a voltage of a transmission path outgoing signal is at the same level as a first reference voltage or exceeds the first reference voltage. Then, a second clock is input and a slew rate of an output buffer is increased or decreased so that a phase of the second clock coincides with a phase of a second differential buffer output signal which rises when a voltage of a transmission path output signal is at the same level as a second reference voltage or exceeds the second reference voltage.

Abstract: A data output driver and a semiconductor memory device having the same are disclosed.

Abstract: A buffer circuit, system, and method are provided. The buffer circuit includes a control circuit coupled to an output of the buffer, or possibly to an output of the first stage of a buffer. A pre-charge circuit is also provided coupled to bias an input of the control circuit to a voltage value approximately near a threshold voltage of the control circuit. The pre-charge bias amount is slightly less than the amount needed to place the control circuit in a high current conduction state. A coupling circuit is thereafter used and adapted to couple an input voltage applied to the buffer circuit to the input of the control circuit. This causes the control circuit to enter the high current conduction state. Depending on the input impedance of the coupling circuit, by pre-charging the coupling circuit input, less time is needed to cause the coupling circuit to enter and thereafter leave a high current conduction state.

Abstract: A data bus inversion (DBI) circuit includes at least one DBI block configured to invert an input data signal based on the logic state of input data bits. The DBI block includes a comparison deciding unit configured to generate, in a first mode, a comparison signal based on the number of changed bits by comparing respective bit signals of the input data signal and a previous input data signal. The comparison deciding unit generates an inversion control signal which controls whether the input data will be inverted or not. In a second mode, the comparison deciding unit generates an inversion control signal based on the predominant logic state of the input data signal bits. A data converting unit is configured to invert the input data signal in response to the inversion control signal. Method embodiments are also disclosed.

Abstract: The present invention relates to an output driver circuit for a semiconductor memory device, in particular, a memory device using a DDR II concept or a concept similar thereto, which can reduce a variation in the slew rate of an output driver thereof between maximum and minimum values, while satisfying requirements of characteristics associated with slew rate.

Abstract: A noise removal circuit of the present invention comprises a 180-degree odd multiple shifting section for outputting a 180-degree shifted signal that is phase-shifted from an input signal by an odd multiple of 180 degrees and difference output section for outputting a difference between the input signal and the 180-degree shifted signal. The noise removal circuit comprises a 360-degree shifting section for outputting a 360-degree shifted signal that is phase-shifted from an input signal by an integral multiple of 360 degrees and sum output section for outputting a sum of the input signal and the 360-degree shifted signal.

Abstract: In one embodiment of the invention, a programmable termination structure has first and second termination circuits for corresponding pads and a programmable connection therebetween. The first termination circuit supports first and second sets of termination schemes. A shared resistor is part of at least one termination scheme in each set. The first termination circuit supports a termination scheme between the first pad and a user-defined node connected to an on-chip capacitor such that first pad is connected via the termination scheme to the on-chip capacitor. Control circuitry automatically turns on and off a termination scheme for bidirectional signaling supported by the first termination circuit, wherein (1) the control circuitry turns off the termination scheme if an output buffer is configured to present outgoing signals at the first pad and (2) the control circuitry turns on the termination scheme if the output buffer is disabled in order to terminate incoming signals received at the first pad.

Abstract: Methods and apparatus for selectively allowing and disallowing changes to an impedance control signal applied to bus driver circuits coupling a device or system to a common, shared bus where impedance of the bus may vary over time. Well known impedance sensing circuits may be coupled to a common bus, such as a PCI bus, and may be used to generate an impedance control signal to be applied to well-known bus driver circuits, including, for example, PCI bus driver circuits, to vary the drive level of such bus driver circuits in accordance with the present electrical impedance sensed on the bus. Features and aspects hereof permit selectively allowing and disallowing changes to such impedance control signals as applied to the driver circuits based upon the present state of the bus and/or the present state of signals driven on the bus by the system embodying the features and aspects hereof.

Abstract: There is provided a data acceleration device comprising a pull-up driver for driving a pull-up in response to the signal level on a first node, a pull-down driver for driving a pull-down in response to the signal level on the first node, a first pull-up circuit for pull-up driving a second node which is electrically coupled with the first node, in response to an output signal from the pull-up driver, a first pull-down circuit for pull-down driving the second node, in response to an output signal from the pull-down driver, a delay circuit for delaying a signal from the second node by a preset time to output a delayed signal, a first switch for switching an operation of the first pull-up circuit in response to an output signal from the delay circuit, and a second switch for switching an operation of the first pull-down circuit in response to the output signal from the delay circuit. Also, there is presented a data transmission apparatus including the data acceleration device.

Abstract: An efficient design methodology in accordance with the present invention is described for reducing the leakage power in CMOS circuits. The method and apparatus in accordance with the present invention yields better leakage reduction as the threshold voltage decreases and hence aids in further reduction of supply voltage and minimization of transistor sizes. Unlike other leakage control techniques, the technique of the present invention does not need any control circuitry to monitor the states of the circuit. Hence, avoiding the sacrifice of obtained leakage power reduction in the form of dynamic power consumed by the additional circuitry to control the overall circuit states.

Abstract: A differential buffer circuit includes a current source, a current sink, and a switching circuit connected to the current source at a first node and connected to the current sink at a second node. The switching circuit is operative to selectively control a direction of current flowing through differential outputs of the buffer circuit in response to at least a first control signal. The buffer circuit further includes a common mode detection circuit and a common mode control circuit. The common mode detection circuit is operative to detect an output common mode voltage of the buffer circuit and to generate a second control signal representative of the output common mode voltage. The common mode control circuit includes a first terminal connected to the current source and a second terminal connected to the current sink. The common mode control circuit is operative to selectively control the output common mode voltage of the buffer circuit as a function of the second control signal.

Abstract: Systems and methods are provided using common-mode-voltage bias circuitry to make common-mode-voltage adjustments to differential driver circuitry in integrated circuit differential communications links. Adjustable bias circuitry may be controlled using static and dynamic control signals. Dynamic control signals can be produced by core logic on a programmable logic device or other integrated circuit. Static control signals can be produced by programmable elements. Bias circuit adjustments made at one end of a differential link can be used to improve performance at either end of the link or can be used to improve power consumption or to balance power and performance considerations. The same integrated circuit design can be used in both AC-coupled and DC-coupled environments. The bias circuitry can be formed from an adjustable current source and adjustable resistor. The current source and adjustable resistors can be controlled by the same control signals.

Abstract: An output circuit has an output transistor, or a complementary pair of output transistors, that generate a bi-level voltage signal with a high output level and a low output level. The signals applied to the gates of the output transistors have high and low levels that are more narrowly separated than are the output high and low levels. For example, one gate signal may swing between the output high level and an intermediate level, and another gate signal may swing between the output low level and the same or a different intermediate level. The relatively narrow voltage swing reduces current consumption, and the intermediate level or levels can be adjusted to adjust the rise time and fall time of the output signal.

Abstract: Programmable logic devices, such as field programmable gate arrays, may have input/output (I/O) circuitry that can be programmed for either differential or single-ended signaling. I/O pins coupled to such programmable I/O circuitry typically have high parasitic input pin capacitance during differential signaling. I/O pins may also have high parasitic input pin inductance. Additional impedance circuit elements such as capacitive or inductive devices are coupled in the programmable I/O circuitry to produce a compensatory impedance that reduces, if not substantially eliminates, the effects of the parasitic input pin capacitance and/or inductance during differential signaling.