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A Dependable SRAM with 7T/14T Memory Cells
Hidehiro FUJIWARA Shunsuke OKUMURA Yusuke IGUCHI Hiroki NOGUCHI Hiroshi KAWAGUCHI Masahiko YOSHIMOTO
Publication
IEICE TRANSACTIONS on Electronics
Vol.E92-C
No.4
pp.423-432 Publication Date: 2009/04/01 Online ISSN: 1745-1353
DOI: 10.1587/transele.E92.C.423 Print ISSN: 0916-8516 Type of Manuscript: Special Section PAPER (Special Section on Low-Leakage, Low-Voltage, Low-Power and High-Speed Technologies for System LSIs in Deep-Submicron Era) Category: Keyword: SRAM, dependability, quality of a bit,
Full Text: PDF>>
Summary:
This paper proposes a novel dependable SRAM with 7T/14T memory cells, and introduces a new concept, "quality of a bit (QoB)" for it. The proposed SRAM has three modes: a normal mode, high-speed mode, and dependable mode, and dynamically scales its reliability, power and speed by combining two memory cells for one-bit information (i.e. 14 T/bit). By carrying out Monte Carlo simulation in a 65-nm process technology, the minimum voltages in read and write operations are improved by 0.21 V and 0.26 V, respectively, with a bit error rate of 10-8 kept. In addition, we confirm that the dependable mode achieves a lower bit error rate than the error correction code (ECC) and multi module redundancy (MMR). Furthermore, we propose a new memory array structure to avoid the half-selection problem in a write operation. The respective cell area overheads in the normal mode are 26% and 11% in the cases where additional transistors are pMOSes and nMOSes, compared to the conventional 6T memory cell.
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