Abstract: A high-speed differential comparator circuit is provided with an accurately adjustable threshold voltage. Differential reference voltage signals are provided to control the threshold voltage of the comparator. The common mode voltage of the reference signals preferably tracks the common mode voltage of the differential high-speed serial data signal being processed by the comparator circuit.

Abstract: Circuits and a method for tuning an integrated circuit (IC) are disclosed. The IC includes a storage circuit coupled to receive a data signal, a clock input signal and a reset signal. The storage circuit may be used to generate a clock signal. The reset signal is supplied by a reset circuit. The reset circuit may include one or more logic gates to generate the reset signal. The reset circuit receives a phase shifted version of the clock input signal and the reset signal is generated based on the phase shifted version of the clock input signal. In one embodiment, the reset signal is a series of pulses generated at specific intervals to shift the output of the storage circuit from logic high level to logic low level.

Abstract: A loss-of-signal detector includes digital and analog monitoring of incoming data. The incoming signal is compared digitally to at least one predetermined pattern that may indicate a loss of signal, and also is monitored by an analog detector that detects transitions in the data. If the digital comparison fails to match any of the at least one predetermined pattern, or if transitions are detected by the analog monitoring, even if the digital comparison produces a pattern match, then loss of signal is not indicated.

Abstract: A charge pump circuit includes at least one switching transistor and a level-shifter. The level-shifter has a cross-coupled pair of transistors. The level-shifter shifts a voltage of a first input signal to generate a level-shifted signal. The level-shifted signal controls a conductive state of the switching transistor to regulate an output voltage of the charge pump. A feedback loop circuit includes a detector and a charge pump. The detector compares an input signal to a feedback signal to generate first and second output signals. The charge pump includes at least two thin-oxide switching transistors and a level-shifter in another embodiment. The level-shifter shifts a voltage of the first output signal of the detector to generate a level-shifted signal. The two switching transistors are driven by the level-shifted signal and the second output signal of the detector to regulate an output voltage of the charge pump.

Abstract: A voltage-controlled oscillator operates at high frequency without high gain by dividing the frequency range into a plurality of subranges, which preferably are substantially equal in size. Within any subrange, the full extent of variation in the control signal changes the frequency only by the extent of the subrange. The gain is thus substantially equal to the gain one would expect for the full frequency range, divided by the number of subranges. The subrange may be selected manually, or by an initial calibration process. In one embodiment, the oscillator includes a voltage-to-current converter and a current-controlled oscillator, with a current mirror arrangement. In that embodiment, selection of the subrange may be controlled by turning on the correct number of current legs.

Abstract: A method for improving analog circuits performance using a circuit design using forward bias and a modified mixed-signal process is presented. A circuit consisting plurality of NMOS and PMOS transistors is defined. The body terminal of the NMOS transistors are coupled to a first voltage source and the body terminal of the PMOS transistors are coupled a second voltage source. Transistors in the circuit are selectively biased by applying the first voltage source to the body terminal of each selected NMOS transistor and applying the second voltage source to the body terminal of each selected PMOS transistor. In one embodiment, the first voltage source and the second voltage source are modifiable to provide forward and reverse bias to the body terminal of the transistors.

Abstract: Pre-emphasis may be able to operate in either of two modes. In a first mode, when one bit has a same value as the bit that immediately preceded it, an output signal for said one bit is based on a first electrical current reduced by a second electrical current. Otherwise the output signal for said one bit is based on the first current without regard for the second current. The second mode may be similar to the first mode when said one bit has the same value as the immediately preceding bit; but otherwise the output signal for said one bit is based on the first current increased by the second current. As an alternative to using the immediately preceding bit (as in the above “post-tap” operation), the immediately succeeding (following) bit may be used in generally the same way (in so-called “pre-tap” operation).

Abstract: A phase interpolator circuit includes first and second low pass filter circuits and a multiplier circuit. The first low pass filter circuit increases a common mode voltage of a clock signal to generate a first varying signal. The second low pass filter circuit increases a common mode voltage of a clock signal to generate a second varying signal. The first low pass filter circuit can include a first variable capacitance, and the second low pass filter circuit can include a second variable capacitance. The multiplier circuit has a first input coupled to the first low pass filter circuit and a second input coupled to the second low pass filter circuit. The multiplier circuit generates a third varying signal in response to the first and the second varying signals. The phase interpolator circuit generates a phase shift in the third varying signal.

Abstract: Signal detection circuitry for a serial interface oversamples the input—i.e., samples the input multiple times per clock cycle—so that the likelihood of missing a signal is reduced. Sampling may be done with a regenerative latch which has a large bandwidth and can latch a signal at high speed. The amplitude threshold for detection may be programmable, particularly in a programmable device. Thus, between the use of a regenerative latch which is likely to catch any signal that might be present, and the use of oversampling to avoid the problem of sampling at the wrong time, the likelihood of failing to detect a signal is greatly diminished. Logic, such as a state machine, may be used to determine whether the samples captured s do or do not represent a signal. That logic may be programmable, allowing a user to set various parameters for signal detection.

Abstract: A transmitter that includes a first phase locked loop (PLL) and a second PLL coupled to the first PLL is described. In one implementation, the first PLL is an inductance-capacitance (LC) type PLL and the second PLL is a ring type PLL. Also, in one embodiment, the transmitter further includes a PLL selection multiplexer coupled to the first and second PLLs, where the PLL selection multiplexer receives an output of the first PLL and an output of the second PLL and outputs either the output of the first PLL or the output of the second PLL. In one implementation, a control signal for controlling selection by the PLL selection multiplexer is programmable at runtime. In one implementation, the transmitter of the present invention further includes a clock generation block coupled to the PLL selection multiplexer, a serializer block coupled to the clock generation block and a transmit driver block coupled to the serializer block.

Abstract: More accurate signal detection circuitry in serial interfaces, particularly on a programmable integrated circuit device, such as a PLD, includes a high-speed, high-resolution, high-bandwidth comparator, along with digital filtering, to reduce the effect of process, temperature or supply variations. The comparator is used to compare a direct input signal with a programmable reference voltage, and, in a preferred embodiment, can detect the signal level within 8 mV accuracy. The output of the comparator may then be digitally filtered. Preferably, both a high-pass digital filter and a low-pass analog filter may be used to eliminate glitches and low-frequency noise. Preferably, the digital filters are programmable to adjust the sensitivity to noise. The filtered output is then latched and output to indicate receipt or loss of signal. This signal detect circuitry can operate reliably at data rates as high as 7 Gbps.

Abstract: An integrated circuit device such as a programmable logic device (“PLD”) includes a plurality of blocks of legacy circuitry. These legacy blocks leave at least one corner of the device unoccupied by such legacy circuitry. This at least one corner is used for relatively newly developed circuitry so as to simplify and speed the design of relatively new circuitry, to avoid having to significantly redesign any of the legacy circuitry to give the device the capabilities of the new circuitry, etc. The relatively newly developed circuitry may be high-speed serial data signal interface (“HSSI”) circuitry that is capable of operating at serial data rates faster than any legacy HSSI circuitry on the device.

Abstract: A method for improving analog circuits performance using a circuit design using forward bias and a modified mixed-signal process is presented. A circuit consisting plurality of NMOS and PMOS transistors is defined. The body terminal of the NMOS transistors are coupled to a first voltage source and the body terminal of the PMOS transistors are coupled a second voltage source. Transistors in the circuit are selectively biased by applying the first voltage source to the body terminal of each selected NMOS transistor and applying the second voltage source to the body terminal of each selected PMOS transistor. In one embodiment, the first voltage source and the second voltage source are modifiable to provide forward and reverse bias to the body terminal of the transistors.

Abstract: An integrated circuit (e.g., a programmable integrated circuit such as a programmable microcontroller, a programmable logic device, etc.) includes programmable circuitry and 10 Gigabit Ethernet (10 GbE) transceiver circuitry. The programmable circuitry and the transceiver circuitry may be configured to implement the physical (PHY) layer of the 10GbE networking specification. This integrated circuit may then be coupled to an optical transceiver module in order to transmit and receive 10 GbE optical signals. The transceiver circuitry and interface circuitry that connects the transceiver circuitry with the programmable circuitry may be hard-wired or partially hard-wired.

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: Transmitter driver circuitry for outputting a high-speed serial data signal (e.g., in the range of about 10 gigabits per second or higher) includes H-tree driver circuitry having only a main driver stage and a post-tap driver stage. At least one transistor in the H-tree driver circuitry is constructed and connected to provide electrostatic discharge protection. PMOS and NMOS current sources are used for the H-tree driver circuitry to enhance power supply noise rejection.

Abstract: A loss-of-signal detector includes digital and analog monitoring of incoming data. The incoming signal is compared digitally to at least one predetermined pattern that may indicate a loss of signal, and also is monitored by an analog detector that detects transitions in the data. If the digital comparison fails to match any of the at least one predetermined pattern, or if transitions are detected by the analog monitoring, even if the digital comparison produces a pattern match, then loss of signal is not indicated.