Abstract: A circuit (e.g., a receiver) has a delay loop (e.g., a voltage-controlled delay loop) and (at least) two phase detectors (PDs), where each PD compares a different pair of clock signals generated by the delay loop. The outputs of the different PDs are then used to generate a control signal for adjusting the delays provided by the delay elements in the delay loop. In one implementation, the control signal indicates that a delay adjustment should be made only if both PDs agree on that adjustment. This multiple-PD technique can reduce jitter that could otherwise result from a non-50% duty cycle in the reference clock signal used by the delay loop to generate its multiple clock signals.

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 sigma-delta delay control in a Delay-Locked-Loop that employs a delay line to generate a clock signal based on a reference signal. A first value is generated if a clock signal has a time lead relative to a reference signal; and a second value is generated if a clock signal has a time lag relative to a reference signal. The first and second values are accumulated to generate an N bit digital word; and the N bit digital word is reduced to an M bit digital word, where M is less than N. Thereafter, the M bit digital word can be converted to an analog bias signal. The reducing step can be performed, for example, by a sigma-delta modulator. The high frequency quantization noise generated by the sigma-delta modulator can be filtered using a low pass filter. The converting step can be performed by a digital-to-analog converter, such as a master/slave digital-to-analog converter.

Abstract: The present invention addresses the generation of a controlled clock source for use in trimming VCDL delay line output clocks. In this trimming process, adjustments are made for static variations in these output clocks. The invention's use of a controlled clock source eliminates the need for this trimming process to be conducted in real time and reduces the expense of the circuitry required.

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: 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: The present invention synchronizes signals generated and used in different clock domains. The invention is applicable to a CDR circuit in which phase adjustment of a multiphase clock to the phase of incoming data is implemented by controlling phase offsets from the PLL frequency relative to data sampling points Si and transition sampling points Ti. In particular, these offsets are controlled by both coarse and fine adjustments. Typically CDR circuits employ feedback phase control information being supplied to the VCDL. The above described adjustments result in these phase control signals having an arbitrary and time-changing relation to the PLL clock. By properly selecting an appropriate edge of the PLL clock signal, the present invention synchronizes these phase control signals into the PLL clock domain in order to apply VCDL control in a synchronous manner.

Abstract: The invention is a method and apparatus for ensuring synchronization for digital communication between a transmitting and a receiving device, particularly when the clock and/or frame synchronization is sourced from a different location than the transmit data.

Abstract: The various embodiments of the invention provide an apparatus, system and method for data content deskewing among a plurality of data channels for data synchronization. The various embodiments determine whether a data alignment signal has been written, for each data channel of the plurality of data channels, such as a comma character. When a data alignment signal has been written in a data channel of the plurality of data channels, the embodiments determine a corresponding channel location of the data alignment signal for each data channel having the data alignment signal. When each data channel of the plurality of data channels has the data alignment signal, and when the data alignment signal is to be read on a next read cycle in at least one data channel, the various embodiments move a corresponding read pointer for each data channel of the plurality of data channels to the corresponding channel location of the data alignment signal.

Abstract: A circuit (e.g., a receiver) has a delay loop (e.g., a voltage-controlled delay loop) and (at least) two phase detectors (PDs), where each PD compares a different pair of clock signals generated by the delay loop. The outputs of the different PDs are then used to generate a control signal for adjusting the delays provided by the delay elements in the delay loop. In one implementation, the control signal indicates that a delay adjustment should be made only if both PDs agree on that adjustment. This multiple-PD technique can reduce jitter that could otherwise result from a non-50% duty cycle in the reference clock signal used by the delay loop to generate its multiple clock signals.

Abstract: Methods and apparatus are provided for generating a frequency with a predefined offset from a reference frequency. A spread spectrum generator circuit is disclosed that comprises a voltage controlled delay loop for generating a plurality of signals having a different phase; and at least one interpolator for processing at least two of the signals to generate an output signal having a phase between a phase of the at least two of the signals, wherein the output is varied between a phase of the at least two of the signals to generate the spread spectrum. A spread spectrum having a frequency lower than an applied clock signal is generated using a continuous phase delay increase and a spread spectrum having a frequency higher than the clock signal is generated using a continuous phase delay decrease.

Abstract: A delay loop (e.g., a voltage-controlled delay loop) has (at least) two devices (e.g., interpolators) for generating clock signals for injection into the delay elements of the delay loop in a leap-frog manner, in which, while one interpolator is generating the clock signal currently selected for injection, the other interpolator can be controlled to generate the next clock signal to be selected for injection. This leap-frog technique can provide more settling time for generating injected clock signals than implementations that rely on a single interpolator.

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: The various embodiments of the invention provide an apparatus, system and method of testing a serializer and deserializer data communication apparatus (SERDES). The serializer and deserializer data communication apparatus has a plurality of serialize data communication channels adapted to convert parallel data to serial data and a plurality of deserialize data communication channels adapted to convert serial data to parallel data. An exemplary method provides for coupling an output of a serialize data communication channel and an input of a deserialize data communication channel to provide a serial data loop-back connection and coupling an output of a deserialize data communication channel and an input of a serialize data communication channel to provide a parallel data loop-back connection.

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 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 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.

Abstract: The present invention utilizes a parallel sampled multi stage decimated digital loop filter for clock and data recovery function. In particular, the present invention provides multiple sampling clocks, with these clocks having sampling clock phases separated in time. These clocks are used in conjunction with multiple data detectors and phase detectors to efficiently process received analog signals in a decimated loop filter system.

Abstract: An ADSL front end is implemented with an adaptive AM interference canceller to cancel out either a carrier signal of an interfering AM radio signal, or a carrier signal and its sidebands of an interfering AM radio signal, from a received ADSL signal. By canceling an interfering AM radio signal rather than simply filtering out the relevant interfered with frequency band, the interfered with frequency band remains useable for ADSL transmission. In one embodiment, a reference AM radio receiver is either fixedly or adaptively tuned to the carrier frequency of an interfering AM radio station, and the received signal in the frequency band surrounding that carrier frequency is digitized and provided to an adaptive interference canceller. The adaptive interference canceller adaptively adjusts a time delay and phase of the generated AM interference signal to optimize cancellation at a hybrid of the same AM radio signal received as interference over a subscriber line.