Semiconductor device with thermal fault detection

1. A semiconductor device comprising:

a semiconductor chip including an active area;

a temperature sensor arrangement that provides a measurement signal dependent on a temperature in or close to the active area; and

an evaluation circuit that is configured to;

compare the measurement signal with a first threshold and to signal an over-temperature when the measurement signal crosses the first threshold in a first direction,

count a number of times the measurement signal crosses the first threshold in the first direction, and

provide a signal indicating that the measurement signal has crossed the first threshold in the first direction a predefined maximum number of times.

2. The semiconductor device of claim 1 , wherein the evaluation circuit comprises a comparator which is configured

to set an over-temperature signal when the measurement signal rises above crosses the first threshold in the first direction thus signalling an over-temperature; and

To reset the over-temperature signal when the measurement signal crosses a second threshold in a second direction opposite the first direction.

3. The semiconductor device of claim 2 , wherein the evaluation circuit comprises a counter receiving the over-temperature signal and configured to count number of transitions from a reset-state to a set-state in the over-temperature signal.

4. The semiconductor device of claim 3 , wherein the counter is further configured

to set an overflow signal when a counter value reaches a predefined maximum value; and

to reset the overflow signal in response to a reset signal.

5. The semiconductor device of claim 4 , wherein the evaluation circuit further comprises a gate circuit receiving the over-temperature signal and the overflow signal and providing an enable/disable signal indicating, by a respective logic level, an over-temperature and/or an overflow of the counter.

6. The semiconductor device of claim 1 , further comprising a control circuit that is configured to deactivate and/or to power down the semiconductor device when the evaluation circuit signals an over-temperature and/or when the evaluation circuit signals that the measurement signal has crossed the first threshold in the first direction the predefined maximum number of times.

7. The semiconductor device of claim 6 , wherein the control circuit is configured to deactivate and/or to power down the semiconductor device when the evaluation circuit signals an over-temperature.

8. The semiconductor device of claim 6 , wherein the control circuit is configured to deactivate and/or to power down the semiconductor device when the evaluation circuit signals that the measurement signal has crossed the first threshold in the first direction the predefined maximum number of times.

9. The semiconductor device of claim 6 , wherein the control circuit is configured to deactivate and/or to power down the semiconductor device when the evaluation circuit signals an over-temperature and when the evaluation circuit signals that the measurement signal has crossed the first threshold in the first direction the predefined maximum number of times.

10. The semiconductor device of claim 1 , wherein the semiconductor device comprises a semiconductor switch having a load current path forming the active area of the semiconductor chip.

11. The semiconductor device of claim 10 , further comprising a control circuit that is configured to generate a driver signal for setting the switching state of the semiconductor switch in accordance with an input signal.

12. The semiconductor device of claim 7 , wherein the control circuit is configured to blank an input signal of a semiconductor switch, thus inhibiting an activation of the semiconductor switch in response to an over-temperature signal and/or when measurement signal has crossed the first threshold in the first direction the predefined maximum number of times.

13. A method for operating a semiconductor device comprising a semiconductor chip including an active area, the method comprising:

providing a measurement signal dependent on a temperature in or close to the active area;

comparing the measurement signal with a first threshold;

signalling an over-temperature when the measurement signal the first threshold in a first direction; and

counting a number of times the measurement signal crosses the first threshold in the first direction; and

signalling when the measurement signal crosses the first threshold in the first direction a predefined maximum number of times.

14. The method of claim 13 , wherein providing the measurement signal comprises:

measuring a first temperature representative of a temperature present at the active area;

measuring a chip temperature remote from the active area of the semiconductor chip; and

providing a signal representative of a difference between the first temperature and the chip temperature as the measurement signal.

15. The method of claim 13 , wherein signalling an over-temperature comprises:

setting an over-temperature signal when the measurement signal crosses the first threshold in the first direction, thus signalling over-temperature; and

resetting the over-temperature signal when the measurement signal crosses a second threshold in a second direction opposite the first direction.

16. The method of claim 15 , further comprising:

combining the over-temperature signal and an overflow signal indicating that the measurement signal has crossed the first threshold in the first direction the predefined maximum number of times.

17. The method of claim 13 , further comprising deactivating and/or powering down the semiconductor device in response to an enable/disable signal indicating that either an over-temperature or that the measurement signal has crossed the first threshold in the first direction the predefined maximum number of times.

18. The method of claim 13 , further comprising deactivating and/or powering down the semiconductor device in response to an enable/disable signal indicating that an over-temperature is reached.

19. The method of claim 13 , further comprising deactivating and/or powering down the semiconductor device in response to an enable/disable signal indicating that the measurement signal has crossed the first threshold in the first direction the predefined maximum number of times.

20. The method of claim 13 , further comprising deactivating and/or powering down the semiconductor device in response to an enable/disable signal indicating that both an over-temperature and that measurement signal has crossed the first threshold in the first direction the predefined maximum number of times.

21. A method of operating a semiconductor switch, the method comprising:

enabling the semiconductor switch;

operating the semiconductor switch in a toggle mode after activating the switch, operating the semiconductor switch in the toggle mode comprising

deactivating the semiconductor switch when a temperature of the semiconductor exceeds a first temperature threshold, and

re-activating the semiconductor switch when a temperature of the semiconductor switch falls below a second threshold;

counting a number of times the temperature of the semiconductor switch transitions from below the first threshold to above the first threshold while in the toggle mode; and

determining when the counted number of times exceeds a predefined number of times.

22. The method of claim 21 , further comprising:

exiting the toggle mode when the counted number of times exceeds a predefined number of times based on the determining, exiting the toggle mode comprising disabling the switch.

23. The method of claim 21 , wherein the predefined number of times is 32.