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Designs for two novel multilevel magnetic random access memory (MRAM) concepts are presented in this paper along with their associated control circuit architectures. Both the ChiralMEM and 3-D-MRAM concepts contain eight states with distinct electrical resistances, giving a 3 bit-per-cell capacity. Operation of the two memory concepts are presented along with designs for the circuitry in particular focusing on the conversion of three conventional binary bits to octal encoded data and the required sequence for writing eight states per cell using current-driven magnetic fields. Discrimination and subsequent conversion of the eight readout resistance levels back to three conventional binary bits are discussed along with the write sequence for controlling arrays of multibit memory cells.
Date of Publication: Jan. 2012