US 7,321,507 B2
Reference cell scheme for MRAM
Hsu Kai Yang, Pleasanton, Calif. (US); Po-Kang Wang, San Jose, Calif. (US); and Xizeng Shi, Fremont, Calif. (US)
Assigned to MagIC Technologies, Inc., Milpitas, Calif. (US); and Applied Spintronics, Inc., Milpitas, Calif. (US)
Filed on Nov. 21, 2005, as Appl. No. 11/284,299.
Prior Publication US 2007/0115717 A1, May 24, 2007
Int. Cl. G11C 7/00 (2006.01)
U.S. Cl. 365—158  [365/171; 365/173] 67 Claims
OG exemplary drawing
 
1. An MRAM reference cell sub-array for providing a mid-point reference current to a plurality of sense amplifiers associated with an MRAM array comprising:
a plurality of MRAM cells arranged in rows and columns;
a plurality of bit lines, each bit line associated with a free magnetic layer of each MRAM cell of a column of the plurality of MRAM cells, and
a coupling to connect the bit lines of pairs of the columns of the plurality of MRAM cells together,
wherein a pair of the MRAM cells of said pair of columns are on a common row of said MRAM cells and a first of said pair of MRAM cells is programmed to a first magneto-resistive state and a second of said pair of MRAM cells is programmed to a second magneto-resistive state such that when one row of MRAM cells are selected for read, said pair of MRAM cells are placed in parallel to generate said mid-point reference current.