Method and apparatus for MRAM sense reference trimming

摘要

A trimming process for setting a reference current used in operating an MRAM module comprising an operational MRAM cell coupled to a bit line, multiple reference MRAM cells coupled to a reference bit line, and a sense amplifier coupled to the bit line and the reference bit line is disclosed in some embodiments. The process includes applying a bit line reference voltage to the reference bit line to provide a reference cell current formed by a sum of respective currents through the plurality of reference MRAM cells. The reference cell current is detected. A determination is made as to whether the detected reference cell current differs from a target reference cell current. The bit line reference voltage is varied, or a sensing ratio of the sense amplifier is varied, if it is determined that the detected reference cell current differs from the target reference cell current.

主权项

1. A memory apparatus comprising:
a plurality of operational magneto-resistive random access memory (MRAM) cells arranged in an array of rows and columns; a plurality of pairs of reference MRAM cells, each pair corresponding to a same row and column as a corresponding operational cell; a plurality of sense amplifiers associated with respective columns; a plurality of word lines configured to select respective rows; wherein a first subset of the pairs of reference cells conforms to a predetermined pattern assigning a first state to a first positional one, and a second state to a second positional one, of each pair of reference cells in the first subset, and a pair not in the first subset does not conform to the predetermined pattern, said pair not in the first subset including a cell stuck at the first state and the other cell set in the second state.