A 1.6-GB/s data-rate 1-Gb synchronous DRAM with hierarchical square-shaped memory block and distributed bank architecture

This paper describes key techniques for a 1.6-GB/s high data-rate 1-Gb synchronous DRAM (SDRAM). Its high data transfer rate and large memory capacity are targeted to the advanced unified memory system in which a single DRAM (array) is used as both the main memory and the three-dimensional (3-D) graphics frame memory in a time sharing fashion. The 200-MHz high-speed operation is achieved by the unique hierarchical square-shaped memory block (SSMB) layout and the novel distributed bank (D-BANK) architecture. A 0.29 μm² cell and 581.8 mm² small die area are achieved using 0.15-μm CMOS technology. The ×61 chip uses 196-pin BGA type chip-scale-package (CSP). Implementation of a built-in self-test (BIST) circuit with a margin test capability is also described