Look-ahead built-in self tests with temperature elevation of functional elements

1. A method for identifying a potential future failing functional element in an integrated circuit during normal operation of the integrated circuit, the method comprising:

determining whether the functional element of the integrated circuit is in an idle cycle;

elevating the temperature of the functional element above a normal operating temperature when the functional element is determined to be in the idle cycle;

performing a stress test of the functional element while the temperature of the functional element is at the elevated temperature and the functional element is in the idle cycle; and

if the functional element fails the stress test, indicating that the functional element is a potential future failing functional element.

2. The method described in claim 1 , wherein elevating the temperature of the functional element above the normal operating temperature further comprises applying a stress temperature input to the functional element.

3. The method described in claim 2 , wherein applying the stress temperature input to the functional element further comprises toggling a logic input to the functional element with a logic signal pattern at a clock rate that is faster than a normal internal clock signal used by the functional element.

4. The method described in claim 3 , wherein the logic input is toggled at twice the normal internal clock signal used by the functional element.

5. The method described in claim 2 , wherein applying the stress temperature input to the functional element further comprises driving a supply voltage input of the functional element with a voltage that is higher than a normal operating voltage of the functional element.

6. The method of claim 2 , further comprising discontinuing the application of the stress temperature input prior to performing the stress test of the functional element.

7. The method described in claim 1 , wherein performing a stress test further comprises providing a margining test voltage to the functional element.

8. The method described in claim 1 , wherein performing a stress test further comprises providing a stress clock signal wherein a pulse of the stress clock signal terminates earlier than a contemporary pulse of a normal internal clock signal used by the functional element.

9. The method described in claim 8 , wherein each pulse of the stress clock signal is approximately equal to each pulse of the normal internal clock signal minus a design margin.

10. The method described in claim 1 , wherein performing a stress test further comprises:

providing a margining test voltage to the functional element; and

providing a stress clock signal to the functional element.

11. The method described in claim 10 , wherein each pulse of the stress clock signal is approximately equal to each pulse of the normal internal clock signal minus a design margin.

12. The method described in claim 1 , wherein performing a stress test further comprises running a standard test on the functional element.

13. The method described in claim 12 , wherein the standard test is performed using the normal internal clock signal of the functional element.

14. The method described in claim 1 , further comprising measuring the elevated temperature of the functional element.

15. The method described in claim 14 , further comprising correlating the measured temperature of the functional element with the stress temperature input if the functional element fails the stress test.

16. An integrated circuit device comprising:

a functional element; and

an operational stress test circuit coupled to the functional element and operable during normal operation of the integrated circuit device to elevate the temperature of the functional element above a normal operating temperature and to perform stress testing on the functional element when the functional element is in an idle cycle and at the elevated temperature.

17. The integrated circuit device described in claim 16 , wherein the operational stress test circuit further comprises:

an idle cycle detect circuit for determining when the functional element is in an idle cycle;

an operational stress test controller coupled to the idle cycle detect circuit, the operational stress test controller further operable to indicate if the functional element fails the stress testing; and

a stress temperature generator coupled to the operational stress test controller, the stress temperature generator operable to elevate the temperature of the functional element above the normal operating temperature.

18. The integrated circuit device described in claim 17 , wherein the operational stress test circuit further comprises a stress clock generator coupled to the operational stress test controller, the stress clock generator operable to generate a stress clock signal.

19. The integrated circuit device described in claim 17 , further comprising a temperature sensor coupled to the functional element and to the operational stress test controller for measuring the elevated temperature of the functional element.

20. The integrated circuit device described in claim 17 , wherein the stress temperature generator is operable to elevate the temperature of the functional element by toggling a logic input to the functional element with a logic signal pattern at a clock rate that is faster than a normal internal clock signal used by the functional element.

21. The integrated circuit device described in claim 17 , further comprising a high supply voltage generating circuit coupled to the operational stress controller and the stress temperature generator, the high supply voltage generating circuit operable to elevate the temperature of the functional element by driving a supply voltage input of the functional element with a voltage that is higher than a normal operating voltage of the functional element.

22. The integrated circuit device described in claim 20 , wherein the stress temperature generator further comprises a 2-to-1 pass-gate multiplexer circuit to provide the logic signal pattern to toggle the logic input to the functional element.

23. The integrated circuit device described in claim 16 , further comprising a built-in repair circuit for repairing the functional element when the functional element fails the stress test.

24. An integrated circuit device comprising:

a functional element; and

an operational stress test circuit coupled to the functional element and operable during normal operation of the integrated circuit device to elevate the temperature of the functional element above a normal operating temperature and to perform stress testing on the functional element when the functional element is in an idle cycle and at the elevated temperature, the operational stress test circuit further comprising;

an idle cycle detect circuit for determining when the functional element is in an idle cycle;

a stress temperature generator coupled to the operational stress test controller, the stress temperature generator operable to elevate the temperature of the functional element above the normal operating temperature; and

an operational stress test controller coupled to the idle cycle detect circuit, the operational stress test controller further operable to indicate if the functional element fails the stress testing.

25. The integrated circuit device described in claim 24 , wherein the stress temperature generator is operable to elevate the temperature of the functional element by toggling a logic input to the functional element with a logic signal pattern at a clock rate that is faster than a normal internal clock signal used by the functional element.

26. The integrated circuit device described in claim 25 , wherein the stress temperature generator further comprises a 2-to-1 pass-gate multiplexer circuit to provide the logic signal pattern to toggle the logic input to the functional element.

27. The integrated circuit device described in claim 24 , further comprising a high supply voltage generating circuit coupled to the operational stress controller and the stress temperature generator, the high supply voltage generating circuit operable to elevate the temperature of the functional element by driving a supply voltage input of the functional element with a voltage that is higher than a normal operating voltage of the functional element.