Thresholding Decision-Directed Descent (T3D): A Tuning Solution for DDR5 DRAM DFEs

Emerging memory technologies, such as DDR5, offer increased data rates and storage capacities, at the expense of signal integrity challenges. To address these challenges, the DDR5 standard incorporates a four-tap decision feedback equalizer (DFE). As elaborated in this article, known methods for DFE tuning are limited due to interface complexity and distinct equalization requirements for DDR5. We propose a decision-directed DFE tuning method called thresholding decision-directed descent (T3D). By leveraging DDR5 architectural features, our novel method tracks the eye envelope as it opens, which facilitates rapid convergence compared to the state of the art. To validate the performance of T3D, silicon measurements are presented alongside a virtual testbench methodology. By demonstrating the high correlation between silicon and simulation results, the virtual testbench can be beneficial for the design, validation, and prototyping of future DFE tuning methods.