IEICE Transactions on Electronics
Online ISSN : 1745-1353
Print ISSN : 0916-8524
Special Section on Analog Circuits and Related SoC Integration Technologies
Subthreshold SRAM with Write Assist Technique Using On-Chip Threshold Voltage Monitoring Circuit
Kei MATSUMOTOTetsuya HIROSEYuji OSAKINobutaka KUROKIMasahiro NUMA
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2011 Volume E94.C Issue 6 Pages 1042-1048

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Abstract

We propose a subthreshold Static Random Access Memory (SRAM) circuit architecture with improved write ability. Even though the circuits can achieve ultra-low power dissipation in subthreshold digital circuits, the performance is significantly degraded with threshold voltage variations due to the fabrication process and temperature. Because the write operation of SRAM is prone to failure due to the unbalance of threshold voltages between the nMOSFET and pMOSFET, stable operation cannot be ensured. To achieve robust write operation of SRAM, we developed a compensation technique by using an adaptive voltage scaling technique that uses an on-chip threshold voltage monitoring circuit. The monitoring circuit detects the threshold voltage of a MOSFET with the on-chip circuit configuration. By using the monitoring voltage as a supply voltage for SRAM cells, write operation can be compensated without degrading cell stability. Monte Carlo simulations demonstrated that the proposed SRAM architecture exhibits a smaller write operation failure rate and write time variation than a conventional 6T SRAM.

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© 2011 The Institute of Electronics, Information and Communication Engineers
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