Abstract-An analysis for calculating data-dependent jitter (DDJ) in a first-order system is introduced. The predicted DDJ features unique threshold crossing times with self-similar geometry. An approximation for DDJ in second-order systems is described in terms of the damping factor and natural frequency. Higher order responses demonstrate conditions under which unique threshold crossing times do not exist and total jitter is minimized. The DDJ predictions are verified with jitter measurements in a bandwidth-limited amplifier. The predictions for both firstand second-order systems anticipate the features of the observed jitter.Index Terms-Data-dependent jitter (DDJ), intersymbol interference, jitter.
An eye-opening monitor (EOM) architecture that can capture a two-dimensional (2-D) map of the eye diagram of a highspeed data signal has been developed. Two single-quadrant phase rotators and one digital-to-analog converter (DAC) are used to generate rectangular masks with variable sizes and aspect ratios. Each mask is overlapped with the received eye diagram and the number of signal transitions inside the mask is recorded as error. The combination of rectangular masks with the same error creates error contours that overall provide a 2-D map of the eye. The authors have implemented a prototype circuit in 0.13-m standard CMOS technology that operates up to 12.5 Gb/s at 1.2-V supply. The EOM maps the input eye to a 2-D error diagram with up to 68-dB mask error dynamic range. The left and right halves of the eyes are monitored separately to capture horizontally asymmetric eyes. The chip consumes 330 mW and operates reliably with supply voltages as low as 1 V at 10 Gb/s. The authors also present a detailed analysis that verifies if the measurements are in good agreement with the expected results.
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