IEEE paper_256 kb 65 nm 8T Subthreshold SRAM

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IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 43, NO. 1, JANUARY 2008

A 256 kb 65 nm 8T Subthreshold SRAM
Employing Sense-Amplifier Redundancy

Naveen Verma, Student Member, IEEE, and Anantha P. Chandrakasan, Fellow, IEEE

Abstract-Aggressively scaling the supply voltage of SRAMs greatly minimizes their active and leakage power, a dominating portion of the total power in modern ICs. Hence, energy constrained applications, where performance requirements are secondary, benefit significantly from an SRAM that offers read and write functionality at the lowest possible voltage. However,bit-cells and architectures achieving very high density conventionally
fail to operate at low voltages. This paper describes a high density SRAM in 65 nm CMOS that uses an 8T bit-cell to achieve a minimum operating voltage of 350 mV. Buffered read
is used to ensure read stability, and peripheral control of both the bit-cell supply voltage and the read-buffer’s foot voltage enable sub- write and read without degrading the bit-cell’s density.The plaguing area-offset tradeoff in modern sense-amplifiers is alleviated using redundancy, which reduces read errors by a factor of five compared to device up-sizing. At its lowest operating voltage, the entire 256 kb SRAM consumes 2.2 W in leakage
power.

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bucuo...

ralphtw

65nm 8t !!!