Methods and systems for protection from over-stress

1. A circuit, comprising:

a temperature rate sensor configured to monitor the temperature of a semiconductor device during a first state and selectively switch the semiconductor device from the first state to a second state if the temperature increases at a rate that has a predetermined relationship with a temperature rate function, the temperature rate sensor comprising:

a temperature sensor configured to provide the temperature of the semiconductor device;

a differentiator configured to provide a differentiated temperature by differentiating the temperature; and

a comparator configured to compare the differentiated temperature to an adjustable reference level representative of the temperature rate function, and to provide a comparator output value therefrom; and

a logic circuit that is coupled to an output node of the comparator, wherein the logic circuit utilizes the comparator output value to provide a logic control signal to switch the semiconductor device from the first state to the second state.

2. The circuit of claim 1 wherein the semiconductor device comprises a MOSFET.

3. A circuit for protection from over-stress, comprising:

a temperature rate sensor configured to monitor a temperature of a semiconductor device and selectively provide an output signal based on whether the temperature increases at a rate that has a predetermined relationship with a temperature rate function;

an integrator configured to, based on the output signal, selectively integrate the temperature during an integration period; wherein the semiconductor device is turned off if the integrated temperature measured over the integration period has a predetermined relationship with an integrator reference level.

4. The circuit of claim 3 , further comprising:

an inductor configured to generate flyback energy when turned from an on-state to an off-state by the semiconductor device;

wherein the circuit is configured to provide a diagnostic fault flag if the flyback energy causes the rate of temperature increase to have the predetermined relationship with the temperature rate function.

5. The circuit of claim 3 , wherein the temperature rate sensor comprises:

a temperature sensor configured to provide the temperature of the semiconductor device; and

a differentiator configured to aid in designating the start of the integration period.

6. The circuit of claim 5 wherein the temperature rate sensor further comprises:

a comparator configured to compare an output of the differentiator to a reference level, and to provide a comparator output value therefrom; and

a time period circuit configured to receive the comparator output value and provide the integration period therefrom.

7. The circuit of claim 6 wherein the temperature rate sensor further comprises:

a second comparator configured to compare the integrated temperature to an integrator temperature function, and provide a second comparator output value therefrom;

wherein the second comparator output value can facilitate switching the semiconductor device from a first state to a second state.

8. A method for protecting a semiconductor device from over-stress, comprising:

monitoring the temperature of a semiconductor device during an on-state;

comparing a temperature rate associated with the monitored temperature to a temperature rate function;

selectively integrating the temperature of the semiconductor device over a time window, where the selective integration is based on the comparison of the temperature rate to the temperature rate function; and

comparing the integrated temperature to an integrator reference level to facilitate switching the device from the on-state to an off-state.

9. The method of claim 8 , wherein the integrating starts at a time related to when the monitored temperature favorably compares to the temperature rate function.

10. The method of claim 9 , further comprising:

measuring the absolute temperature of the semiconductor device; and

switching the semiconductor device to an off-state if the absolute temperature exceeds a maximum temperature.

11. A circuit for protection from over-stress, comprising:

means for monitoring the temperature of a semiconductor device during an on-state and for comparing a temperature rate associated with the monitored temperature to a temperature rate function; and

circuitry to facilitate switching the semiconductor device from a first state to a second state if the temperature rate favorably compares to the temperature rate function;

integration means for integrating the temperature of the semiconductor device over a time window; and

means for providing an enabling signal that is representative of the time window for which integration is carried out.

12. The circuit of claim 11 , further comprising:

means for comparing the integrated temperature to a integrated temperature function to facilitate switching the device from the on-state to an off-state.

13. The method of claim 12 , further comprising:

diagnostic circuitry for delivering a diagnostic signal from the circuit, wherein the diagnostic signal is indicative of an excessive temperature in the circuit.

14. A circuit for protection from over-stress, comprising:

a temperature rate sensor configured to monitor a temperature of a semiconductor device and integrate the temperature during an integration period, the temperature rate sensor comprising:

a temperature sensor configured to provide the temperature of the semiconductor device;

a differentiator configured to aid in designating the start of the integration period; and

an integrator configured to integrate the temperature during the integration period;

wherein the integration period relates to a time at which a rate of temperature increase has a pre-determined relationship with a temperature rate function.

15. A circuit for protection from over-stress, comprising:

a temperature rate sensor configured to monitor a temperature of a semiconductor device and integrate the temperature during an integration period;

wherein the integration period relates to a time at which a rate of temperature increase has a pre-determined relationship with a temperature rate function; and

an inductor configured to generate flyback energy when turned from an on-state to an off-state by the semiconductor device;

wherein the circuit is configured to provide a diagnostic fault flag if the flyback energy causes the rate of temperature increase to have the predetermined relationship with the temperature rate function.