R&D: Stub Equalizer for Bidirectional and Single-Ended Channels in NAND Memory Storage Device Systems

IEEE Transactions on Electromagnetic Compatibility has published an article written by Taelim Song, Electromagnetic Compatibility Laboratory, Missouri University of Science and Technology, Rolla, MO 65401 USA, Jongjoo Lee, Solution Design and Integration Group, SK Hynix Inc., Seongnam-si 13558 South Korea, and Chulsoon Hwang, Electromagnetic Compatibility Laboratory, Missouri University of Science and Technology, Rolla, MO 65401, USA.

Abstract: “In memory devices, such as solid-state drive, multitopology is used for interfaces where multiple memory packages are connected to a controller using a branched transmission line. Impedance mismatching caused by the branches and unwanted reflection from deactivated packages inevitably degrades signal quality, limiting the data rate of the interface. In this article, a simple stub equalizer is proposed to improve the data rate of the memory interface. An open-ended stub is placed between a transmitter and a receiver, and the length, impedance, and location of the stub line are determined to properly cancel the reflection from other branches. Parameters are optimized based on the peak distortion analysis and an exhaustive search considering both read and write modes. The improvements are validated through eye-diagram simulations.“