Non-volatile static random access memory and methods for using same

Abstract

The state of a memory cell is stored by selectively imbalancing threshold voltages of storage elements of the memory cell. The threshold voltages may be selectively imbalanced by pulsing the supply voltage for the memory cell from an operating voltage level to a programming voltage level. This may be accomplished by raising the supply voltage from the operating voltage level to the programming voltage level for a period of time sufficient to store the state of the memory cell by monitoring the leakage current from the programming voltage level such that it just falls below a preestablished limit. Alternatively, the supply voltage may be repeatedly toggled between the operating voltage level and the programming voltage level for fixed time intervals until the state of the memory cell is stored. The number of toggling operations may be determined by monitoring the leakage current such that it just falls exceeds a predetermined limit. The programming voltage level may be approximately twice the operating voltage level or greater. Selectively imbalancing the threshold voltages of the storage elements may be accomplished by creating a first electric field within a first of the storage elements to tunnel electrons off of a floating gate of the first storage element and creating a second electric field within a second of the storage elements to inject the electrons onto a floating gate of the second storage element. Preferably, these electric fields are created simultaneously by applying the programming voltage to the memory cell.