MRAM WITH CURRENT-BASED SELF-REFERENCED READ OPERATIONS

摘要

A magnetoresistive memory stores logic values in high and low resistance states of magnetic tunnel junction elements. Instead of comparing the resistance of elements to a fixed threshold to discern a logic state, the resistances of elements are self-compared before and after imposing a low resistance state. A measure of the resistance of an element in its unknown resistance state is stored, for example by charging a capacitor to a voltage produced when read current bias is applied. Then the element is written into its low resistance state and read current bias is applied again to develop another voltage, representing the low resistance state. A comparison circuit using current summing and an offset providing a minimum difference tolerance determines whether the resistance of the element was changed or remained the same. This determines the logic state of the element.