Neighbor-A-Posteriori Information Assisted Cell-State Adaptive Detector for NAND Flash Memory

Abstract

Cell-to-Cell interferences (CCIs), which arise from adjacent cells through parasitic coupling-capacitance, severely degrade the performance of threshold voltage detection. Pre-processing and post-processing methods have been proposed to mitigate the effect of CCIs on threshold voltage variation. The performance of the aforementioned methods heavily depends on the accuracy of the threshold voltages adjacent to the victim cells. However, to obtain high accuracy, these methods requires multi-sensing operations, thus significantly resulting in high detection latency. In this letter, a novel non-uniform detection scheme based on the threshold voltage of cell states, which is referred to as the cell-state adaptive detection (CSAD), is proposed to adapt the shifts of the threshold voltages. Then, the neighbor-a-posteriori information is exploited to mitigate the overcompensation phenomenon and further improve the performance of the CSAD under the block read mode scenario. Simulation results show that the proposed CSAD scheme and its improved version not only achieve better bit-error-rate performance but also keep lower detection latency compared with the existing detection schemes.