Statistical Signal Integrity Analysis on DFE with Nonideal Latch Model

This paper introduces the nonideal latch model for the decision feedback equalizer (DFE) for statistical signal integrity (SI) analysis. The DFE equalizes inter-symbol-interference (ISI) noise from the channel in the time domain. The nonideal DFE may propagate an error due to the ISI noise, and the nonideal latch in the DFE may also generate a bit error in the DFE operation. The dynamic latch in the slicer of the DFE circuit amplifies the received signal in a recursive manner. During the amplification, the voltage difference ebetween the signal and the threshold voltage may be less amplified when the amplification time is not enough. Thus, the nonideal dynamic latch is another error source in the DFE operation. In order to reflect the effect of the nonideal latch, the gray zone is defined based on the transfer function of the dynamic latch with iterations. In other words, the gray zone is approximated with the Gaussian distribution and reflected into the statistical eye diagram. As a result of the nonideal latch model, the statistical eye diagram has blurred probability density functions (PDFs).