Abstract: Circuitry for adaptive signal equalizing with coarse and fine boost controls by providing multiple serially coupled stages of parallel controllable DC and AC signal gains with coarse and fine gain controls provided across all stages.

Abstract: Circuitry for adaptive signal equalizing with coarse and fine boost controls by providing multiple serially coupled stages of parallel controllable DC and AC signal gains with coarse and fine gain controls provided across all stages.

Abstract: A system and a method are disclosed for providing a parameterized analog feedback loop for continuous time adaptive equalization that incorporates low frequency attenuation gain compensation. N adaptive equalizer stages are coupled in series and a slicer circuit is coupled to the last (Nth) adaptive equalizer stage. A single equalizer adaptation control loop controls the frequency response of the adaptive equalizer stages to compensate for the attenuation of a lossy channel. The single equalizer adaptation control loop also compensates for the direct current (DC) loss in the lossy channel by modulating a bias current in the slicer circuit to scale the low frequency feedback with adaptation coefficients that correlate with channel length.

Abstract: A system and method is disclosed for providing a clock and data recovery circuit with a fast bit error rate self test capability. A bit error rate test control unit is provided that causes the clock and data recovery circuit to sample data adjacent to an edge of a bit period to create errors at a relatively high bit error rate. This is accomplished by intentionally introducing an interpolator offset in a phase position of a data clock signal. The test control unit generates a first bit error rate and then subsequently generates a second bit error rate. The test control unit then uses the values of the first and second bit error rates to extrapolate a value of bit error rate for the clock and data recovery circuit that corresponds to a zero value of interpolator offset.

Abstract: A system and method is disclosed for providing a clock and data recovery circuit with a self test capability. A test control unit is provided that causes the clock and data recovery circuit to continuously alter a phase of an interpolated clock signal. A user selects a preselected bit pattern that causes the digital control circuitry of the clock and data recovery circuit to advance or retard the phase of the interpolated clock signal. The test control unit compares the advanced or retarded phase of the interpolated clock signal with a reference clock signal to determine a frequency difference between the two clock signals. The test control unit uses the frequency difference to determine the test status of the clock and data recovery circuit.

Abstract: A system and method is disclosed for providing a clock and data recovery circuit that comprises a low jitter data receiver. The low jitter data receiver comprises a phase interpolator, an amplifier unit and a data sampling comparator. The phase interpolator and the amplifier unit provide the data sampling comparator with a single ended clock signal that is relatively immune to power supply noise. The data sampling comparator samples an input data stream with minimal jitter due to power supply noise. The data sampling comparator consumes less static power than a current mode logic D flip flop and also has output levels that are compatible with complementary metal oxide semiconductor (CMOS) logic.

Abstract: A system and method is disclosed for providing a fast turn on bias circuit that permits a fast transition from an idle “power down” state to an active “power up” state in current mode logic (CML) transmitter output circuits. The invention comprises a capacitor coupled to a bias transistor and a charge switch circuit for controlling the operation of the capacitor. The capacitor has a value of capacitance that is equal in magnitude and opposite in sign to the Miller coupling capacitance in the bias transistor. The capacitor compensates for the Miller coupling capacitance within the bias transistor in less than ten nanoseconds. This permits a CML transmitter to more quickly restart the transmission of data after an active state has been initiated.

Abstract: An operational amplifier having a low impedance input and a high current gain output. The operational amplifier comprises: 1) a first N-channel transistor having a source coupled to the low impedance input of the operational amplifier; 2) a first constant current source coupled between the source of the first N-channel transistor and ground; 3) a first amplifier stage having an input coupled to the first N-channel transistor source and an inverting output coupled to a gate of the first N-channel transistor; 4) a second amplifier stage having an input coupled to a drain of the first N-channel transistor and an output coupled to the high current gain output of the operational amplifier; and 5) an internal compensation capacitor coupled between the input and the output of the second amplifier stage.

Abstract: A band-gap reference circuit with averaged current mirror offsets is provided that includes a differential amplifier circuit, a low current transistor circuit, a high current transistor circuit, and a configuration circuit. The differential amplifier circuit includes a first input node operable to receive a first input signal, a second input node operable to receive a second input signal, and an output node operable to generate an output signal based on the input signal difference. The low current transistor circuit is coupled to the differential amplifier circuit and is operable to receive the output signal and to generate the first input signal based on the output signal. The high current transistor circuit is coupled to the differential amplifier circuit and is operable to receive the output signal and to generate the second input signal based on the output signal. The configuration circuit is coupled to the low current transistor circuit and to the high current transistor circuit.

Abstract: Three-state binary adders are disclosed for use in pipelined analog-to-digital converters. According to one advantageous embodiment, a three-state binary adder is provided for use in a digital signal processing system. The three-state binary adder is operable to generate binary codes consisting of three states, namely, “00”, “01” and “10.

Abstract: There is disclosed a test multiplexer having over voltage protection for use in integrated circuitry, along with methods of operating the same. An exemplary test multiplexer according to one embodiment of the present invention includes a plurality of MOSFET devices and over voltage protection circuitry. The plurality of MOSFET devices, including both p-type and n-type MOSFET devices, cooperate to pass an input signal to an output signal line of the test multiplexer while the test multiplexer is enabled. The over voltage protection circuitry is biased so that a difference between the input signal voltage and a bias voltage does not exceed breakdown when the test multiplexer is disabled. An important aspect hereof is that the test multiplexer is compliant to input voltages that exceed the positive supply rail, and is capable of sustaining a high or otherwise out of threshold single ended voltage at the input without latching up.

Abstract: An operational amplifier having a low impedance input and a high current gain output. The operational amplifier comprises: 1) a first N-channel transistor having a source coupled to the low impedance input of the operational amplifier; 2) a first constant current source coupled between the source of the first N-channel transistor and ground; 3) a first amplifier stage having an input coupled to the first N-channel transistor source and an inverting output coupled to a gate of the first N-channel transistor; 4) a second amplifier stage having an input coupled to a drain of the first N-channel transistor and an output coupled to the high current gain output of the operational amplifier; and 5) an internal compensation capacitor coupled between the input and the output of the second amplifier stage.

Abstract: There is disclosed a comparator comprising: 1) a first comparison circuit capable of receiving an input signal, wherein the first comparison circuit is enabled and compares the signal when a received LATCH signal is enabled and is disabled when the received LATCH signal is disabled; and 2) a second comparison circuit coupled to the input signal in parallel with the first comparison circuit, wherein an input stage of the second comparison circuit is substantially identical to an input stage of the first comparison circuit. The second comparison circuit is enabled and compares the input signal when the received LATCH is signal is disabled and is disabled when the received LATCH signal is enabled.

Abstract: A low power analog equalizer is disclosed that provides up to twenty decibels (20 dB) of alternating current gain in a single stage of analog signal equalization. The analog equalizer comprises an operational amplifier coupled to two half circuits. Each half circuit comprises an impedance network capable of receiving an analog input voltage and generating a current signal that is inversely proportional to frequency, a current steering digital to analog converter capable of adjusting the gain of the operational amplifier, and a transistor and an amplifier coupled in a cascode configuration to create a low impedance node at the output of the impedance network. The analog equalizer is fabricated with 0.18 micron CMOS technology and operates at 1.8 volts.

Abstract: There is disclosed an amplifier for operating from a power supply having a first voltage level. The amplifier comprises: 1) a plurality of thick-oxide field effect transistors, each of the plurality of thick-oxide field effect transistors having a relatively thick oxide layer and fabricated using a first process such that the each thick-oxide field effect transistor can withstand a gate-to-source difference, a gate-to-drain difference, and a gate-to-bulk difference at least equal to a first maximum operating voltage, wherein the first.

Abstract: There is disclosed a test multiplexer having over voltage protection for use in integrated circuitry, along with methods of operating the same. An exemplary test multiplexer according to one embodiment of the present invention includes a plurality of MOSFET devices and over voltage protection circuitry. The plurality of MOSFET devices, including both p-type and n-type MOSFET devices, cooperate to pass an input signal to an output signal line of the test multiplexer while the test multiplexer is enabled. The over voltage protection circuitry is biased so that a difference between the input signal voltage and a bias voltage does not exceed breakdown when the test multiplexer is disabled. An important aspect hereof is that the test multiplexer is compliant to input voltages that exceed the positive supply rail, and is capable of sustaining a high or otherwise out of threshold single ended voltage at the input without latching up.

Abstract: A strobed comparator circuit with reduced signal propagation time has a regenerative latch in which, during the reset phase of operation, its output nodes are discharged to a common potential which is close to the regenerative voltage level of the cross-coupled transistors forming such regenerative latch rather than to circuit ground. Accordingly, overall signal propagation time is reduced by the amount of reduction in charging time necessary for one of the discharged nodes to recharge above the threshold voltage of one of the cross-coupled latch transistors. Also included is an output monitoring circuit which determines whether the regenerative latch has remained in a metastable state.

Abstract: A sample and hold (S/H) circuit with common mode differential signal feedback for converting single-ended signals to differential signals includes a feedback loop for the input switched capacitor circuit to ensure that the input common mode voltage for the differential amplifier is maintained at a known value during the hold phase of operation. The feedback loop consists of a three-input error amplifier which monitors the two voltages at the differential input terminals of the differential amplifier in relation to the common mode reference voltage and generates a feedback voltage which is applied to the input terminals of the input switched capacitor circuit during the hold phase of operation. If both of the differential input terminal voltages are either more negative or more positive than the common mode reference voltage then the feedback voltage generated by the error amplifier is made more positive or negative, respectively.

Abstract: A phase-locked loop (PLL) frequency synthesizer is described which incorporates a fractional pulse swallowing circuit. The fractional pulse swallowing circuit does not add or delete pulses but extends or shortens pulses by a fractional amount. This avoids large phase errors generated by a phase detector in the PLL. In the preferred embodiment, the PLL uses a voltage controlled oscillator (VCO) formed of a ring oscillator. The outputs of the stages of the ring oscillator are applied to input terminals of a multiplexer. The multiplexer is controlled at certain times to output a different tapped signal from the ring oscillator to effectively adjust the phase of the signal output from the multiplexer. By so controlling the multiplexer, fractional pulses are subtracted or added at intervals to either increase or decrease the average frequency of the signal output from the multiplexer. The output of the VCO is fed back to the input of a phase detector along with a reference frequency.

Abstract: A high speed fully differential operational amplifier with fast settling time for switched capacitor applications includes a high gain active cascode applied to the operational amplifier's input stage transistors to improve the gain, provide a higher output impedance, and thus, reduce the Miller feedback gate drain capacitance of the input stage devices. This improves the speed of the amplifier. A biasing technique is used to keep the active cascodes biased during transient overload so that settling will not be adversely affected during the recovery of the cascodes. A pair of transistors are used to feed forward a fraction of the tail current to "keep-alive" the cascode transistors. In other words, the fraction of the tail current that is fed to the source of the cascode transistors via the keep-alive transistors effectively biases the active cascodes sufficiently so that they do not turn off completely during slewing.