Multi-bit Cells Design for Toggle MRAM Applications

In this paper, a multiple bit cell design is proposed consisting of a stack of multiple toggle MRAM cells connected in series and placed between the x and y write current conductors. The cells in the stack have distinct anisotropy axes. The selective writing is done using a three phases field pulse with field orientation sweeping through the easy axis of the selected toggle cell in the stack. This scheme is quite general and can be adopted for 2-, 4-, 6-,.. bit cells. For simplicity, we use a 4-bit cell to illustrate the concept. We also cover the device implication for up to 6-bit cell.