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: The various embodiments of the invention provide an apparatus, system and method of asynchronous testing a serializer and deserializer data communication apparatus (SERDES) for determining frequency and phase locking to pseudo asynchronous input data having a continual phase offset. An exemplary apparatus includes a data sampler adapted to sample input serial data and to provide output data; a controlled tap delay with a selected tap having a phase offset from the input serial data, in which the selected tap is selectively coupleable to the data sampler to provide pseudo asynchronous input serial data; a first variable delay control adapted to delay a reference frequency provided to the controlled tap delay in response to the pseudo asynchronous input serial data; and a second delay control adapted to adjust the plurality of taps in response to the pseudo asynchronous input serial data.

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 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: 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 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 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: 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: 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.