Device for monitoring the temperature of an element

• US 9,459,157 B2
• Filed: 01/22/2014
• Issued: 10/04/2016
• Est. Priority Date: 12/24/2008
• Status: Active Grant

• Current Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SAS (STMicroelectronics NV)
• Inventors: Fornara, Pascal, Rivero, Christian
• Primary Examiner(s): Noori, Max
• Assistant Examiner(s): WILLIAMS, JAMEL E
• Application Number:
  US14/161,502
• Publication Number:
  US 20140133517A1
• Time in Patent Office: 986 Days
• Field of Search: 374/45, 374/152
• US Class Current: 1/1
• CPC Class Codes: G01K 13/00 Thermometers specially adapted for specific purposes
• CPC Class Codes: H01H 1/0036 Switches making use of microelectromechanical systems [MEMS] for electromagnetic relays H01H50/005; for electrostatic relays H01H59/0009
• CPC Class Codes: H01H 2037/008 Micromechanical switches operated thermally
• CPC Class Codes: H01H 37/46 actuated due to expansion or contraction of a solid deflection of a bimetallic element H01H37/52

Abstract

A device for monitoring the temperature surrounding a circuit, including: a charge storage element; a charge evacuation device; and a thermo-mechanical switch connecting the storage element to the evacuation element, the switch being capable of closing without the circuit being electrically powered, when the temperature exceeds a threshold.

Claims

1. A method for monitoring the temperature of an element comprising:

powering a circuit attached to the element to inject charges into a charge storage element of the circuit;

removing the power from the circuit;

causing an evacuation of the charges from the charge storage element if the temperature exceeds a temperature threshold;

powering the circuit; and

reading an amount of charge present in the charge storage element.

2. A method for monitoring the temperature of an element as defined in claim 1, wherein causing the evacuation of the charges from the charge storage element comprises providing a thermo-mechanical switch connected to the charge storage element and using the thermo-mechanical switch to discharge the charge storage element when the temperature exceeds the temperature threshold.

3. A method for monitoring the temperature of an element as defined in claim 2, wherein causing the evacuation of the charges from the charge storage element comprises discharging the charge storage element through a discharge element connected between the thermo-mechanical switch and a substrate on which the circuit is formed.

4. A method for monitoring the temperature of an element as defined in claim 2, wherein the thermo-mechanical switch is formed of two metal strips having opposite ends separated by a distance that decreases to zero when the temperature exceeds the temperature threshold.

5. A method for monitoring the temperature of an element as defined in claim 1, wherein the charge storage element comprises a floating gate of a floating gate transistor.

6. A method for monitoring the temperature of an element as defined in claim 5, wherein injecting charges into the charge storage element comprises injecting charges into the floating gate of the floating gate transistor.

7. A method for monitoring temperature, comprising:

charging a charge storage element of a temperature monitoring circuit;

discharging the charge storage element in response to the temperature exceeding a temperature threshold; and

monitoring a charge of the charge storage element to determine if the temperature threshold has been exceeded.

8. A method as defined in claim 7, wherein the charge storage element comprises a floating gate of a floating gate transistor.

9. A method as defined in claim 8, wherein charging the charge storage element comprises injecting charge into the floating gate of the floating gate transistor.

10. A method as defined in claim 7, wherein discharging the charge storage element comprises providing a thermo-mechanical switch connected to the charge storage element and using the thermo-mechanical switch to discharge the charge storage element when the temperature exceeds the temperature threshold.

11. A method as defined in claim 10, wherein discharging comprises discharging the charge storage element through a discharge element connected between the thermo-mechanical switch and a substrate on which the temperature monitoring circuit is formed.

12. A method as defined in claim 7, wherein the charge storage element is discharged in response to the temperature exceeding the temperature threshold, with power removed from the temperature monitoring circuit.

13. A method as defined in claim 12, wherein the charge of the charge storage element is monitored with power applied to the temperature monitoring circuit.

14. A method as defined in claim 10, wherein the thermo-mechanical switch is formed of two metal strips having opposite ends separated by a distance that decreases to zero when the temperature exceeds the threshold.

15. A method, comprising:

forming a temperature monitoring circuit, the forming including;

coupling a transistor between a supply voltage and a floating node, the transistor having a gate terminal configured to receive a charge injection control signal;

coupling a charge storage element to the floating node, the charge storage element being configured to store an injected charge;

coupling a thermomechanical switch between a charge evacuation element and the floating node, the thermomechanical switch being configured to discharge the charge storage element through the charge evacuation element when the temperature exceeds a temperature threshold; and

coupling a reading device to the temperature monitoring circuit, the reading device being configured to read an amount of charge present in the charge storage element after at least a portion of the injected charge stored in the charge storage element has been evacuated.

16. The method of claim 15, wherein coupling the reading device to the temperature monitoring circuit includes:

coupling a first input terminal of a comparator to the floating node; and

coupling a second input terminal of the comparator to a reference voltage.

17. The method of claim 15, wherein forming a temperature monitoring circuit further includes:

coupling the charge evacuation element between the thermomechanical switch and a substrate on which the temperature monitoring circuit is formed.

18. The method of claim 15, wherein the thermomechanical switch comprises two metal strips having opposite ends, the opposite ends of the two metal strips being configured to be separated by a distance at temperatures below the temperature threshold, and to contact one another when the temperature exceeds the threshold temperature.

19. The method of claim 18, wherein forming a temperature monitoring circuit includes:

forming the metal strips of the thermomechanical switch in an interconnect stack, the ends of the metal strips being separated by a region in the interconnect stack filled with air.

20. The method of claim 15, wherein forming a temperature monitoring circuit further includes coupling a selection transistor to the gate terminal of the transistor coupled between the supply voltage and the floating node, the selection transistor being configured to supply the charge injection control signal.