摘要:
Serial data signal receiver circuitry for inclusion on a PLD includes a plurality of equalizer circuits that are connected in series and that are individually controllable so that collectively they can compensate for a wide range of possible input signal attenuation characteristics. Other circuit features may be connected in relation to the equalizer circuits to give the receiver circuitry other capabilities. For example, these other features may include various types of loop-back test circuits, controllable termination resistance, controllable common mode voltage, and a controllable threshold for detection of an input signal. Various aspects of control of the receiver circuitry may be programmable.
摘要:
Data signals transmitted over transmission media suffer from attenuation caused by the transmission media. Equalization circuitry may be provided to compensate for attenuation caused by the transmission media. Equalization circuitry may include multiple stages arranged in series to allow the frequency responses of the stages to aggregate together. Each stage may be programmable to insert a zero, which causes the frequency response of the stage to increase in magnitude by 20 dB/decade. The frequency location of the zero may also be programmable to allow each stage to contribute a certain amount of gain for a specific frequency. Each stage may also be programmable to determine the location of poles for reduction of high frequency noise and cross-talk cancellation.
摘要:
Data signals transmitted over transmission media suffer from attenuation caused by the transmission media. Equalization circuitry may be provided to compensate for attenuation caused by the transmission media. Equalization circuitry may include multiple stages arranged in series to allow the frequency responses of the stages to aggregate together. Each stage may be programmable to insert a zero, which causes the frequency response of the stage to increase in magnitude by 20 dB/decade. The frequency location of the zero may also be programmable to allow each stage to contribute a certain amount of gain for a specific frequency. Each stage may also be programmable to determine the location of poles for reduction of high frequency noise and cross-talk cancellation.
摘要:
Serial data signal receiver circuitry for inclusion on a PLD includes a plurality of equalizer circuits that are connected in series and that are individually controllable so that collectively they can compensate for a wide range of possible input signal attenuation characteristics. Other circuit features may be connected in relation to the equalizer circuits to give the receiver circuitry other capabilities. For example, these other features may include various types of loop-back test circuits, controllable termination resistance, controllable common mode voltage, and a controllable threshold for detection of an input signal. Various aspects of control of the receiver circuitry may be programmable.
摘要:
A programmable logic device is provided with adaptive equalization circuitry that is programmable in one or more respects. Examples of the programmable aspects of the equalization circuitry are (1) the number of taps used, (2) whether integer or fractional spaced taps are used, (3) what starting values are used in the computation of coefficient values, (4) whether satisfactory coefficient values are computed only once or on an on-going basis, (5) whether an error signal is generated using a decision directed algorithm or using a training pattern, (6) what training pattern (if any) is used, and/or (7) the location of the sampling point in the bit period of the signal to be equalized.
摘要:
A programmable logic device is provided with adaptive equalization circuitry that is programmable in one or more respects. Examples of the programmable aspects of the equalization circuitry are (1) the number of taps used, (2) whether integer or fractional spaced taps are used, (3) what starting values are used in the computation of coefficient values, (4) whether satisfactory coefficient values are computed only once or on an on-going basis, (5) whether an error signal is generated using a decision directed algorithm or using a training pattern, (6) what training pattern (if any) is used, and/or (7) the location of the sampling point in the bit period of the signal to be equalized.
摘要:
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.
摘要:
Methods and apparatus are provided for generating a clock signal with relatively high bandwidth and relatively low phase noise. A circuit of the invention can include a pair of transistors serially coupled between a signal of relatively high voltage and a source of relatively low voltage, where a voltage of the signal of relatively high voltage can vary according to a voltage of a variable control signal. A gate of one of the pair of transistors can be coupled to an input clock signal, and an output node between the pair of transistors can be coupled to an output clock signal. The circuit can also include a third transistor, whose drain and source are coupled to the output clock signal, and whose gate can be coupled to a gear input signal. This circuit can advantageously operate under at least two different gears, each with different bandwidth and phase noise characteristics.
摘要:
Precision amplitude detection circuitry without pattern dependencies is provided that includes rectifier circuitry to output a rectified voltage signal and delay circuitry to send one or more delayed or phase-shifted versions of a differential signal input to the rectifier circuitry. The delayed versions of the differential signal input may be delayed in order to reduce or eliminate the dips in the input seen by the rectifier. This may help correct for low rectified voltage levels. The signal amplitude detection circuitry of the present invention may be incorporated on the input pin of any programmable logic resource and may be included in communication circuitry of a PLD. The precision amplitude detection circuitry may operate in the Gbps (gigabit per second) range.
摘要:
Signal offset variation caused by transistor variation/mismatch in integrated circuits may be reduced. In one embodiment, a buffer circuit has variable-valued circuit elements. Offset variation measurements are made and the variable-valued circuit elements are calibrated to reduce the measured offset variation. In another embodiment, each amplifying stage of a multi-stage buffer provides variable gain. The total DC gain of the cascade is distributed unevenly across the stages, with more DC gain being provided by amplifier stages at the beginning of the cascade than at the end. An additional pre-amplifier stage can also be provided at the beginning of the cascade.