Abstract: A voltage controlled delay loop and method are disclosed for clock and data recovery applications. The voltage controlled delay loop generates clock signals having similar frequency and different phases. The voltage controlled delay loop comprises a plurality of delay elements; and an input that selectively injects a reference clock into any one of the plurality of delay elements. The plurality of delay elements are connected in series, such as in a loop. In one exemplary implementation, each delay element has an associated multiplexer that selects one of the reference clock and a signal from a previous delay element.

Abstract: Methods and apparatus are provided for improving phase switching and linearity in an analog phase interpolator. A phase interpolator in accordance with the present invention comprises (i) a plurality of tail current sources that are activated for substantially all times when the phase interpolator is operational; (ii) at least two pairs of input transistor devices, wherein one pair of the input transistor devices is associated with a minimum phase of the phase interpolator and another pair of the input transistor devices is associated with a maximum phase of the phase interpolator; and (iii) a plurality of current steering switches that provide currents generated by the plurality of tail current sources to one or more of the at least two pairs of input transistor devices, based on an applied interpolation control signal.

Abstract: A method and apparatus are disclosed for generating phase controlled data, based on a roaming tap interpolator. The present invention recognizes that roaming tap interpolators have inherent nonlinearities and discontinuities at the boundaries of each interpolation region. A roaming tap interpolator is disclosed that shifts the interpolation curve in time in order to avoid the undesired artifacts in the interpolation curve. A roaming tap interpolator generally comprises a plurality of delay elements that delays a first signal to generate a plurality of interpolation regions each having an associated phase; a multiplexer to select one or more of the interpolation regions; and an interpolator to process the selected one or more of the interpolation regions to generate a second signal.

Abstract: Methods and apparatus are provided for improving phase switching and linearity in an analog phase interpolator. A phase interpolator in accordance with the present invention comprises (i) a plurality of tail current sources that are activated for substantially all times when the phase interpolator is operational; (ii) at least two pairs of input transistor devices, wherein one pair of the input transistor devices is associated with a minimum phase of the phase interpolator and another pair of the input transistor devices is associated with a maximum phase of the phase interpolator; and (iii) a plurality of current steering switches that provide currents generated by the plurality of tail current sources to one or more of the at least two pairs of input transistor devices, based on an applied interpolation control signal.

Abstract: Methods and apparatus are provided for improving phase switching and linearity in an analog phase interpolator. A phase interpolator in accordance with the present invention comprises (i) a plurality of tail current sources that are activated for substantially all times when the phase interpolator is operational; (ii) at least two pairs of input transistor devices, wherein one pair of the input transistor devices is associated with a minimum phase of the phase interpolator and another pair of the input transistor devices is associated with a maximum phase of the phase interpolator; and (iii) a plurality of current steering switches that provide currents generated by the plurality of tail current sources to one or more of the at least two pairs of input transistor devices, based on an applied interpolation control signal.

Abstract: A parallel trimming method and apparatus are provided for a voltage controlled delay loop. A plurality of delay units in a voltage controlled delay loop are trimmed. Each delay unit comprises a delay element and a latch buffer. A reference signal is applied to each of the delay units and a position of an edge (such as a rising or falling edge) associated with each of the delay units is identified. The edges of the delay units are then aligned by adjusting a trim setting of the respective latch buffer.

Abstract: Methods and apparatus are provided for improving phase switching and linearity in an analog phase interpolator. A phase interpolator in accordance with the present invention comprises (i) a plurality of tail current sources that are activated for substantially all times when the phase interpolator is operational; (ii) at least two pairs of input transistor devices, wherein one pair of the input transistor devices is associated with a minimum phase of the phase interpolator and another pair of the input transistor devices is associated with a maximum phase of the phase interpolator; and (iii) a plurality of current steering switches that provide currents generated by the plurality of tail current sources to one or more of the at least two pairs of input transistor devices, based on an applied interpolation control signal.

Abstract: Methods and apparatus are provided for maintaining a desired slope of clock edges in a phase interpolator using an adjustable bias. The disclosed phase interpolator comprises at least one delay element to generate at least two interpolation signals each having an associated phase and a variable slope unit associated with each of the at least two interpolation signals, wherein a slope of each of the variable slope units is controlled by a bias signal and is varied based on a data rate of the interpolation signals. The slope is varied to maintain a desired slope of clock edges associated with the interpolation signals. The slope can be maintained, for example, between approximately the value of the delay between consecutive clock edges and twice the value of the delay between consecutive clock edges.

Abstract: A voltage controlled delay loop and method are disclosed for clock and data recovery applications. The voltage controlled delay loop generates clock signals having similar frequency and different phases. The voltage controlled delay loop comprises at least one delay element to generate at least two phases of a reference clock; a central interpolator for interpolating the at least two phases of the reference clock to generate an interpolated signal; and an input that injects the interpolated signal into a delay stage. The central interpolator provides a fine phase control. In addition, a coarse phase control can optionally be achieved by selectively injecting the interpolated signal into a given delay stage. A further voltage controlled delay loop is disclosed with coarse and fine phase control using a number of interpolators.

Abstract: Methods and apparatus are provided for trimming a desired delay element in a voltage controlled delay loop. The disclosed trimming process comprises the steps of obtaining a first phase signal of a reference clock; applying the first phase signal along a first path to the desired delay element and a common delay element connected in series to the desired delay element; applying the reference clock along a second path to a first delay element and the common delay element; measuring a delay difference between the first and second paths at an output of the common delay element; and adjusting a delay of the desired delay element based on the measured delay difference. The trimming method may be repeated for each delay element in a voltage controlled delay loop.

Abstract: A digit signal processor capable of operating at 100 MHZ with a 1.0 volt power supply. The digital signal processor is fabricated by application of strong phase-shift lithography to obtain a 0.12 &mgr;m gate dimension. A dual-mask process is utilized to improve resolution thereby producing high speed, low-voltage processors. A n+/p+ dual-Poly:Si module, and dopant penetration suppression techniques may be utilized.

Abstract: A latch circuit employs a feedback arrangement comprising a transmisson gate circuit that conducts only when the output node is in a mid-voltage state. At the onset of a metastable state, the feedback arrangement forces a receiving node into its previous stable state, thereby forcing the output node into a stable state. This eliminates or reduces the possibility that the latch could remain hung for an indefinite period in a metastable state.

Abstract: After performing a floating point addition, it is desired to normalize the sum; that is, shift the most significant digit of the mantissa into the left-most digit location, and adjust the exponent accordingly. Prior art techniques required performing the addition before calculating the number of shifts required. The present technique determines an approximate shift from the addends during addition, resulting in a significant time saving.

Abstract: An MOS driver circuit which provides full VDD and VSS output logic levels uses a bootstrap capacitor and a delay circuit whose delay is controlled by potential of the terminal which is bootstrapped. Adverse effects of processing variations are limited because the delay time of the delay circuit is determined by the components which selectively control the potential of the bootstrapped terminal.

Abstract: An MOS parallel carry synchronous binary counter/clock rate divider circuit has a chain of simultaneously clocked T flip-flop interconnected by an improved enable logic circuit having a plurality of identical carry stages each associated with a different flip-flop except the first and last flip-flop of the chain. Each carry stage has an input terminal connected to the inverted enable input of its associated flip-flop, an output terminal connected to the inverted enable input of the next flip-flop in the chain, a transmission gate transistor having a conduction channel connected in series between the input and output terminals and a gate connected to the normal output of the associated flip-flop, and a depletion mode load transistor having a conduction channel connected between a VDD power supply terminal and the output terminal and a gate connected to the output terminal.

Abstract: A chain-type ripple-carry generating circuit having a plurality of cascaded stages is provided with a regeneration network in each stage for restoring the logic level of a carry signal propagating through the stage. In one embodiment of the invention the regeneration network is designed to restore a carry-not bit and comprises an MOS transistor having its conduction channel coupled between the input of the stage and a ground terminal, the gate of the transistor being driven by a two-input NOR gate, one input of the NOR gate being connected to receive a precharge clock signal and the other input being connected to the input of the stage. When the precharge clock signal is at a logic "0" level and the input of the stage receives a carry-not bit at a logic "0" level, the NOR gate drives the MOS transistor into conduction causing the input of the stage to be pulled to substantially ground potential.