Adaptive Decision Feedback Equalizer with Hexagon EOM and Jitter Detection

This paper presents an adaptive decision feedback equalizer (DFE) utilizing a hexagon eye-opening monitor to detect both the violation of the minimum eye and the severity of the violation so as to allow different step sizes to be used in search for optimal DFE tap coefficients. In addition, a new slope detection method is used to detect the deviation of received data symbols from the desired one so as to guide the direction of search for the optimal DFE tap coefficients. The proposed adaptive DFE allows designers to freely set DFE constraints such as the minimum vertical eye opening, the minimum horizontal eye opening, and the maximum jitter of the sampling clock so as to address the needs of different applications. To validate its effectiveness, the proposed adaptive DFE is embedded in a 2 Gbps serial link designed in an IBM 130 nm 1.2 V CMOS technology. The link is analyzed using Spectre from Cadence Design Systems with BSIM4 device models. Simulation results demonstrate that the proposed adaptive DFE is capable of opening completely closed data eyes at the far end of a 2-m FR4 channel with 75 % vertical eye opening, 78 % horizontal eye opening, and 21 % data jitter while consuming 17.38 mW.