Transient Cell Supply Voltage Collapse Write Assist Using Charge Redistribution

Abstract

This brief describes a charge redistribution transient cell supply voltage collapse write assist (CR-TVC-WA) for static random access memory. Although wordline underdrive read assist is a requisite for stable read operations in deep submicrometer technologies, it significantly degrades the write ability. To overcome this problem, a transient cell supply voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DD,CELL</sub> ) collapse write assist (TVC-WA) method is widely used, but it consumes a large amount of energy. In the proposed CR-TVC-WA, the virtual cell supply and ground nodes are temporarily floated and connected to each other during the write operation. This improves the write ability and significantly reduces energy consumption. Simulation results indicate that the minimum operation voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MIN</sub> ) is approximately 660 mV when the write operation is performed at 1 GHz and the extra write energy consumption (3.8 fJ) additionally required to satisfy the target yield (6σ) is reduced by 46% compared with that in the conventional TVC-WA (7.0 fJ).