Method of sensing data of a magnetic random access memories (MRAM)

1. A method of sensing a magnetic tunnel junction (MTJ) comprising:

applying a first reference current through the MTJ;

first programming the MTJ to a first value using the first reference current;

detecting the resistance of the first programmed MTJ;

determining if the detected resistance is above a first reference resistor and if so, declaring the MTJ to be at a first state;

if not, determining if the detected resistance is below a second reference resistance and if so, declaring the MTJ to be at a second state;

if not, applying a second reference current through the MTJ and second programming the MTJ to a second value using the second reference current;

detecting the resistance of the second programmed MTJ;

determining if the resistance of the detected second programmed MTJ is above the first reference resistance and if so, declare the MTJ to be at the second state; and

if not, declaring the MTJ to be at the first state and programming the MTJ to the second state.

2. A method of determining reference currents for a magnetic random access memory (MRAM) reference cell of a memory array, the MRAM reference cell being employed when reading MRAM cells of the memory array, the method comprising:

a. programming all of the MRAM cells to a first value by causing their resistances to be at Rlow;

b. reading the memory array;

c. first determining if the MRAM cells of the memory array are at a first state and if so, second determining a first reference current value to be used when reading a MRAM cell of the memory array; and

d. if the MRAM cells of the memory array are not at the first state, reducing the current of the MRAM reference cell and repeating steps c. and d. until all of the MRAM cells of the memory array are at the first state.

3. The method of determining reference currents, as recited in claim 2 , further including,

e. programming all of the MRAM cells to a second value by causing their resistances to be at Rhigh;

f. reading the memory array;

g. third determining if the MRAM cells of the memory array are at a second state and if so, fourth determining a second reference current value to be used when reading a MRAM cell of the memory array; and

h. if the MRAM cells of the memory array are not at the second state, increasing the current of the MRAM reference cell and repeating steps g. and h. until all of the MRAM cells of the memory array are at the second state.

4. The method of determining reference currents, as recited in claim 3 , wherein the first reference current value is Ilref.

5. The method of determining reference currents, as recited in claim 3 , wherein the first reference current value is Ihref.

6. The method of determining reference currents, as recited in claim 3 , wherein the Rlow falls within a low resistance distribution curve and the Rhigh falls within a high resistance distribution curve, the low resistance distribution curve and the high resistance distribution curve overlapping at least in part.

7. The method of determining reference currents, as recited in claim 3 , further including,

applying a first reference current through the MTJ;

first programming the MTJ to a first value using the first reference current;

detecting the resistance of the first programmed MTJ;

determining if the detected resistance is above a first reference resistor and if so, declaring the MTJ to be at a first state;

if not, determining if the detected resistance is below a second reference resistance and if so, declaring the MTJ to be at a second state;

if not, applying a second reference current through the MTJ and second programming the MTJ to a second value using the second reference current;

detecting the resistance of the second programmed MTJ;

determining if the resistance of the detected second programmed MTJ is above the first reference resistance and if so, declare the MTJ to be at the second state; and

if not, declaring the MTJ to be at the first state and programming the MTJ to the second state.