A 38.64-Gb/s Large-CPM 2-KB LDPC Decoder Implementation for nand Flash Memories

The routing congestion over a QC-LDPC decoder with a large circular permutation matrix (CPM) size has long been an obstacle to high throughput designs. This paper presents a large-CPM congestion-free decoder for (18396, 16416) quasi-cyclic Euclidean geometry low-density parity-check (QC-EG-LDPC) code in NAND flash application. Considering area efficiency in scheduling schemes and the array dispersion structure, the Array-Disperse Based Dual Variable Node Unit (VNU) Cluster Architecture fully leverages the code structure to support at least two physical channels of the Open NAND Flash Interface 5.0 (ONFI 5.0). In addition, the proposed congestion-aware analysis and implementation method achieve a highly parallel decoder at a 70% utilization ratio. Implemented in TSMC 28nm process, the presented decoder provides 38.64 Gbps throughput at RBER=1.456% Bi-AWGN channel with an area of 2.97 mm2.