National Semiconductor Corporation

Texas Instruments Corporation

Paul Joseph Kramer

Jered Michael Sandner

Robert Callaghan Taft

Ohad Falik

Vineethraj Rajappan Nair

Alexander Bodem

Filip Savic

Matthew Hansen Childs

An example apparatus includes: first through eighth gated inverters each having inputs and outputs; a first and second inverter each having an input and an output, the output of the first inverter coupled to the input of the second gated inverter, the output of the second inverter coupled to the input of the third gated inverter; the fifth gated inverter coupled to the input of the first gated inverter and the input of the first inverter; the sixth gated inverter coupled to the input of the second inverter and the input of the fourth gated inverter; the seventh gated inverter coupled to the output of the first gated inverter and the output of the third gated inverter; the eighth gated inverter coupled to the output of the second gated inverter and the output of the fourth gated inverter; and a bus-holder circuit between the seventh and eighth gated inverter inputs.

Methods and apparatus to prevent lock-up of high-speed pseudo-differential frequency divider circuits

Clock generation for capturing a repetitive signal relative to a clock includes clock circuitry to provide a clock with active and inactive clock edges within a clock period, and signal capture circuitry to capture repetitive signal transitions at an active clock edge, based on pre-defined setup and hold times which determine a setup/hold window. Clock phase adjustment circuitry is configured to adjust clock phase so that the repetitive signal transitions occur within a signal capture window between setup/hold windows. Clock phase adjustment can be based on: aligning the clock inactive edges to the repetitive signal transitions; and/or averaging successive phase comparisons of the clock and the repetitive signal transitions; and/or selectively performing an initial polarity inversion to generate a polarity inverted clock, and then adjusting clock phase of the polarity inverted clock. An example implementation is JESD204B (subclass1) to adjust DEVCLK phase relative to a SYSREF timing reference control signal.

Meeting setup/hold times for a repetitive signal relative to a clock

The invention produces an output signal that maintains a substantially constant period corresponding to a clock signal. An input signal includes a period that is an integer multiple of the period of the clock signal. The timing or phase of the input signal may shift in comparison to the clock signal resulting in jitter. The invention detects and cancels the jitter by varying a delay between the input signal and the output signal. The delay corresponds to an integer multiple of the period of the clock signal such that a substantially constant period is maintained for the output signal. Alternatively, the intended period for the output signal may be adjusted to match a new period when a determination is made that a sufficient difference exists between the new period of the input signal and the intended period.

Apparatus and method for a jitter cancellation circuit

A method and apparatus are arranged to provide a multi-bit digital signal that represents a normalized percentage of time that a signal is active. The apparatus includes an N-bit counter that is periodically reset to an initialization condition, and a logic block that processes the output of the N-bit counter. The N-bit counter is arranged to evaluate a monitored signal for each cycle of a clock signal, and modify the count accordingly. The logic block is configured to periodically scan the output of the N-bit counter after the expiration of a sampling time interval. The sampling time interval is determined by a timing circuit such as a window counter that is operated from the clock signal. The logic block periodically evaluates the output of the N-bit counter and provides the normalized multi-bit digital signal.

Signal active percentage monitor

A frequency divider circuit utilizes an asynchronous slip request signal to provide an output clock signal according to a programmable divide ratio &ldquo;R&rdquo;. A high frequency input clock signal has a frequency divided by a first factor to produce a divided signal when a slip signal is inactive. The output clock signal is produced by functionally dividing the frequency of the divided signal by a second factor. The second factor is determined by the programmable divide ratio divided by the first factor such that the frequency of the output clock signal is related to the frequency of the input clock signal and the programmable divide ratio. An asynchronous slip request signal is generated when the programmable divide ratio is a non-multiple of the first factor. The asynchronous slip request signal activates the slip signal such that a transition of the divided signal is skipped.

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Fort Collins, CO, United States of America

Paul Joseph Kramer