Programmable and redundant circuitry based on magnetic tunnel junction (MTJ)

1. A programmable circuit, comprising:

a programmable fuse including;

a magnetic tunnel junction (MTJ);

a MTJ control circuit coupled to the MTJ to control the MTJ to cause a breakdown in the MTJ in programming the MTJ, thus forming a breakdown region with a low resistance;

a sensing circuit coupled to the MTJ to sense a voltage under a breakdown condition of the MTJ; and

wherein the magnetization of the MTJ is controlled by a current injected into the MTJ based on a spin-transfer torque effect.

2. The programmable circuit as in claim 1 wherein the programmable fuse includes;

a second MTJ that is connected to the MTJ in series, and

wherein the sensing circuit is coupled to a sensing location in a conductive path between the MTJ and the second MTJ to sense the voltage at the sensing location.

3. The programmable circuit as in claim 1 wherein the programmable fuse includes;

a second circuit element that is connected to the MTJ in series, and

wherein the sensing circuit is coupled to a sensing location in a conductive path between the MTJ and the second circuit element to sense the voltage at the sensing location.

4. The programmable circuit as in claim 3 , wherein:

the second circuit element is a MTJ element.

5. The programmable circuit as in claim 3 , wherein:

the second circuit element is a circuit element different from a MTJ element.

6. The programmable circuit as in claim 5 , wherein:

the second circuit element is a transistor.

7. The programmable circuit as in claim 5 , wherein:

the second circuit element is a resistor.

8. A programmable circuit, comprising:

a programmable fuse including;

a first magnetic tunnel junction (MTJ) and a second MTJ that are connected to each other in series;

a sensing circuit coupled to a sensing location in a conductive path between the first MTJ and second MTJ to sense a voltage at the sensing location;

a first MTJ control circuit coupled to the first MTJ to control the first MTJ; and

a second MTJ control circuit coupled to the second MTJ to control the second MTJ;

wherein one of the first and second MTJ control circuits operates to supply a high voltage to break down a respective MTJ to increase a sensing margin at the sensing location; and

wherein the magnetization of each of the first MTJ and the second MTJ is controlled by a current injected into the MTJ based on a spin-transfer torque effect.

9. A programmable circuit, comprising:

a programmable fuse including;

a magnetic tunnel junction (MTJ);

a circuit element that has a structure different from the MTJ and connected to the MTJ in series;

a sensing circuit coupled to a sensing location in a conductive path between the MTJ and the circuit element to sense a voltage at the sensing location;

a MTJ control circuit coupled to the MTJ to supply a high voltage to break down the MTJ to increase a sensing margin at the sensing location;

a circuit control circuit coupled to the circuit element to control the circuit element; and

wherein the magnetization of the MTJ is controlled by a current injected into the MTJ based on a spin-transfer torque effect.

10. The programmable circuit as in claim 9 , wherein:

the circuit element is a transistor.

11. The programmable circuit as in claim 9 , wherein:

the circuit element is a resistor.

12. A method for providing a programmable circuit, comprising:

providing a programmable fuse including;

connecting a magnetic tunnel junction (MTJ) in a programmable fuse to supply a high resistance or a low resistance to the programmable fuse;

controlling a current injected into the MTJ to cause a breakdown in the MTJ in programming the programmable fuse to form a breakdown region with a low resistance; and

controlling the magnetization of the MTJ by a current injected into the MTJ based on a spin-transfer torque effect.

13. The method as in claim 12 wherein providing a programmable fuse includes;

connecting a second MTJ to the MTJ in series in the programmable fuse;

controlling a current injected into the second MTJ to avoid a breakdown in the second MTJ in programming the programmable fuse to make the second MTJ exhibit a high resistance; and

sensing a voltage at a sensing location in a conductive path between the MTJ and the second MTJ.

14. The method as in claim 12 wherein providing a programmable fuse includes;

connecting a circuit element to the MTJ in series in the programmable fuse, the circuit element being different from a MTJ in structure;

controlling an operating condition of the circuit element in programming the programmable fuse to make the circuit element exhibit a high resistance; and

sensing a voltage at a sensing location in a conductive path between the MTJ and the circuit element.

15. The method as in claim 14 , wherein:

the circuit element is a transistor.

16. The method as in claim 14 , wherein:

the circuit element is a resistor.