Integrated circuit having a switch

1. An integrated circuit having a switch comprising:

first resistivity changing material;

a reference element; and

a sense amplifier coupled to the first resistivity changing material and the reference element and configured to compare a signal from the first resistivity changing material to a signal from the reference element and output a voltage signal for deactivating a failing portion of the integrated circuit based on the comparison.

2. The integrated circuit of claim 1 , wherein the reference element comprises a resistor.

3. The integrated circuit of claim 2 , wherein the first resistivity changing material is selectively coupled to one of a constant voltage and a write pulse generator, and wherein the resistor is coupled to the constant voltage.

4. The integrated circuit of claim 1 , wherein the reference element comprises second resistivity changing material.

5. The integrated circuit of claim 4 , wherein the first resistivity changing material is selectively coupled to one of a constant voltage and a write pulse generator, and wherein the second resistivity changing material is selectively coupled to one of the constant voltage and the write pulse generator.

6. The integrated circuit of claim 3 , wherein the write pulse generator comprises an internal write pulse generator.

7. The integrated circuit of claim 3 , wherein the write pulse generator comprises an external write pulse generator.

8. A reprogrammable switch comprising:

first phase-change material;

second phase-change material; and

a sense amplifier coupled to the first phase-change material and the second phase-change material and configured to compare a signal from the first phase-change material to a signal from the second phase-change material and output a voltage signal based on the comparison for deactivating a failing portion of a chip.

9. The switch of claim 8 , wherein the first phase-change material is selectively coupled to one of a constant voltage and a write pulse generator, and wherein the second phase-change material is selectively coupled to one of the constant voltage and the write pulse generator.

10. The switch of claim 9 , wherein the write pulse generator comprises an internal write pulse generator.

11. The switch of claim 9 , wherein the write pulse generator comprises an external write pulse generator.

12. The switch of claim 8 , wherein the sense amplifier is configured to compare a current through the first phase-change material to a current through the second phase-change material.

13. The switch of claim 8 , wherein the sense amplifier is configured to compare a voltage across the first phase-change material to a voltage across the second phase-change material.

14. An integrated circuit chip comprising:

a reprogrammable switch comprising a first contact, a second contact, and phase-change material between the first contact and the second contact; and

means for deactivating a failing portion of the chip based on a state of the phase-change material and a state of a reference element.

15. The integrated circuit chip of claim 14 , wherein the phase-change material comprises a chalcogenide.

16. The integrated circuit chip of claim 14 , wherein the phase-change material comprises a chalcogen free material.

17. A method for using a reprogrammable switch, the method comprising:

applying a write pulse to first phase-change material to switch a state of the first phase-change material;

applying a first voltage to the first phase-change material and to a reference element;

sensing a first signal from the first phase-change material and a second signal from the reference element;

comparing the first signal to the second signal;

providing a second voltage based on the comparison; and

deactivating a failing portion of an integrated circuit based on the second voltage.

18. The method of claim 17 , wherein applying the first voltage to the reference element comprises applying the first voltage to second phase-change material.

19. The method of claim 17 , wherein applying the first voltage to the reference element comprises applying the first voltage to a resistor.

20. The method of claim 17 , wherein applying the write pulse comprises applying the write pulse from an internal write pulse generator.

21. The method of claim 17 , wherein applying the write pulse comprises applying the write pulse from an external write pulse generator.

22. A method for using a reprogrammable switch, the method comprising:

applying a write pulse to first phase-change material to switch a state of the first phase-change material;

applying a first voltage to the first phase-change material and to a second phase-change material;

sensing a first signal from the first phase-change material and a second signal from the second phase-change material;

comparing the first signal to the second signal;

providing a second voltage based on the comparison; and

deactivating a failing portion of a chip in response to the second voltage.

23. The method of claim 22 , wherein applying the write pulse comprises applying the write pulse from an internal write pulse generator.

24. The method of claim 22 , wherein applying the write pulse comprises applying the write pulse from an external write pulse generator.

25. The method of claim 22 , wherein sensing the first signal from the first phase-change material and the second signal from the second phase-change material comprises sensing a first current through the first phase-change material and a second current through the second phase-change material.

26. The method of claim 22 , wherein sensing the first signal from the first phase-change material and the second signal from the second phase-change material comprises sensing a third voltage across the first phase-change material and a fourth voltage across the second phase-change material.

27. The method of claim 22 , further comprising:

applying a write pulse to the second phase-change material to switch a state of the second phase-change material.

28. A reprogrammable switch comprising:

phase-change material; and

a sense amplifier coupled to the phase-change material and a constant voltage, the sense amplifier configured to compare a voltage across the phase-change material to the constant voltage and output a voltage signal for deactivating a failing portion of an integrated circuit based on the comparison.

29. The switch of claim 28 , wherein the phase-change material is selectively coupled to one of the constant voltage and a write pulse generator.

30. The switch of claim 28 , wherein the write pulse generator comprises an internal write pulse generator.

31. The switch of claim 28 , wherein the write pulse generator comprises an external write pulse generator.

32. An integrated circuit chip comprising:

a switch comprising resistivity changing material;

a reference element; and

a sense amplifier coupled to the switch and providing an output signal based on a state of the switch for deactivating a failing portion of the chip,

wherein the sense amplifier compares a signal provided by the reference element and provides the output signal based on the comparison.