Conexant Systems, Inc.

Steven Beccue

Charles E Chang

Bo Zhang

Anders Kongstad Petersen

Zhihao Lao

An improved flip-flop circuit exhibits a higher phase margin than conventional flip-flop circuits without a substantial increase in operating power. The flip-flop circuit includes a master latch circuit operatively coupled to a slave latch circuit. The flip-flop circuit uses any number of techniques to delay the hold-to-sample transition of the slave latch circuit relative to the sample-to-hold transition of the master latch circuit. The delay enables the flip-flop circuit to better tolerate clock/data timing alignment issues. In a first embodiment, the slave clock signal is delayed relative to the master clock signal. In a second embodiment, the master clock signal buffer is unbalanced such that its duty cycle is skewed to produce unequal sample and hold periods. In a third embodiment, the master latch circuit is unbalanced to create an unequal delay associated with the sampling and holding periods.

High phase margin low power flip-flop

Modern fiber optic networks typically transfer data using encoding in which the clock is transmitted along with the data, for example in NRZ format. In order to use the clock to process the data, the clock signal must be extracted from the data signal. Because the data and clock may travel through different circuit paths they may have different propagation delays and a phase offset between the clock and data may result. Data and clock phase offsets are more problematical as data transmission speed increases. Furthermore the data/phase offset is typically not constant and may change with a variety of variables. To compensate for the changing offset, one or more variable delays are inserted in the phase detector circuitry. The timing of the variable delay is controlled by a bang-bang phase detector, such as an Alexander phase detector, which determines if the clock is leading, lagging, or in phase with the data. The delay control loops are low bandwidth, because the phase offset generally changes slowly, and because the loops should not respond to temporary upsets such as noise spikes. The delay control loops integrate the output of the bang-bang phase detector and use the output to control a decimated up down counter, which is then further used to control one or more variable delays. The counter can be pre-loaded with a default start point, and the bandwidth of the loops can be dynamically adjusted by changing the decimation ratio and sample periods of the loop.

Growing community of inventors

Oxnard, CA, United States of America

Steven Beccue