Trends in Ultralow-Voltage RAM Technology

摘要

This paper describes ultralow-voltage RAM technology for standalone and embedded memories in terms of signal-to-noise-ratio designs of RAM cells and subthreshold-current reduction. First, structures and areas of current DRAM and SRAM cells are discussed. Next, low-voltage peripheral circuits that have been proposed so far are reviewed with focus on subthreshold-current reduction, speed variation, on-chip voltage conversion, and testing. Finally, based on the above discussion, a perspective is given with emphasis on needs for high-speed simple non-volatile RAMs, new devices/circuits for reducing active-mode leakage currents, and memory-rich SOC architectures.