Thermal sensors and methods of operating thereof

• US 9,004,754 B2
• Filed: 06/30/2011
• Issued: 04/14/2015
• Est. Priority Date: 04/22/2009
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Swei, Steven
• Primary Examiner(s): KAPLAN VERBITSKY, GAIL
• Application Number:
  US13/173,112
• Publication Number:
  US 20110255568A1
• Time in Patent Office: 1,384 Days
• Field of Search: 702/130, 702/99, 702/136
• US Class Current: 374/170
• CPC Class Codes: G01K 2219/00 Thermometers with dedicated analog to digital converters
• CPC Class Codes: G01K 7/01 using semiconducting elements having PN junctions G01K7/02, G01K7/16, G01K7/30 take precedence

Abstract

A thermal sensor includes a comparator having a first and second input nodes. A reference voltage generator is electrically coupled with the first input node. The reference voltage generator is configured to provide a reference voltage that is substantially temperature-independent. A temperature sensing circuit is electrically coupled with the second input node. The temperature sensing circuit is configured to provide a temperature-dependent voltage. The temperature sensing circuit includes a current mirror. A first metal-oxide-semiconductor (MOS) transistor is electrically coupled between the current mirror and ground. A first resistor is electrically coupled with the current mirror. A second MOS transistor is electrically coupled with the first resistor in series. The second MOS transistor and the first resistor are electrically coupled with the first MOS transistor in a parallel fashion.

Claims

1. A thermal sensor comprising:

a comparator having a first and second input nodes;

a reference voltage generator electrically coupled with the first input node of the comparator, the reference voltage generator being configured to provide a reference voltage that is substantially temperature-independent; and

a temperature sensing circuit electrically coupled with the second input node of the comparator, the temperature sensing circuit being configured to provide a temperature-dependent voltage, wherein the temperature sensing circuit comprises;

a current mirror;

a first metal-oxide-semiconductor (MOS) transistor electrically coupled between the current mirror and ground, wherein a first node is between the first MOS transistor and the current mirror, and the first node is electrically coupled with the second input node of the comparator;

a first resistor electrically coupled with the current minor, wherein a second node is between the first resistor and the current mirror;

a second MOS transistor electrically coupled with the first resistor in series, wherein the second MOS transistor and the first resistor are electrically coupled with the first MOS transistor in a parallel fashion;

a third MOS transistor electrically coupled with a power source voltage;

a fourth MOS transistor electrically coupled with the third MOS transistor in series;

a second resistor electrically coupled between the first node and a third node between the third and fourth MOS transistors; and

a third resistor electrically coupled between the third node and the second node.

2. The thermal sensor of claim 1, wherein the first and second MOS transistors are operable in a sub-threshold region during a sensing operation of the thermal sensor.

3. The thermal sensor of claim 1, wherein the temperature sensing circuit is a complementary-to-absolute-temperature (CTAT) sensing circuit.

4. The thermal sensor of claim 1, wherein the fourth MOS transistor is operable in a sub-threshold region during a sensing operation of the thermal sensor.

5. The thermal sensor of claim 1, wherein the temperature sensing circuit is a proportional-to-absolute-temperature (PTAT) sensing circuit.

6. The thermal sensor of claim 5, further comprising:

a fifth MOS transistor electrically coupled with a power source voltage, wherein a gate of the fifth MOS transistor is electrically coupled with the current mirror; and

a fourth resistor electrically coupled with the fifth MOS transistor in series, wherein a fourth node between the fifth MOS transistor and the fourth resistor is electrically coupled with the first input node of the comparator.

7. The thermal sensor of claim 1, wherein the current mirror comprises a second comparator.

8. The thermal sensor of claim 7, wherein a first input of the second comparator is connected to the first node, and a second input of the second comparator is connected to the second node.

9. A thermal sensor comprising:

a comparator having a first and second input nodes;

a reference voltage generator electrically coupled with the first input node of the comparator, the reference voltage generator being configured to provide a reference voltage that is substantially temperature-independent; and

a proportional-to-absolute-temperature (PTAT) sensing circuit electrically coupled with the second input node of the comparator, the PTAT sensing circuit being configured to provide a temperature-dependent voltage, wherein the PTAT sensing circuit comprises;

a current mirror;

a first metal-oxide-semiconductor (MOS) transistor electrically coupled between the current mirror and ground, wherein a first node is between the first MOS transistor and the current mirror;

a first resistor electrically coupled with the current mirror, wherein a second node is between the first resistor and the current mirror;

a second MOS transistor electrically coupled with the first resistor in series, wherein the second MOS transistor and the first resistor are electrically coupled with the first MOS transistor in a parallel fashion, and the first and second MOS transistors are operable in a sub-threshold region during a sensing operation of the thermal sensor; and

a third MOS transistor electrically coupled with a power source voltage, wherein a gate of the third MOS transistor is electrically coupled with the current mirror; and

a second resistor electrically coupled with the third MOS transistor in series, wherein a third node between the third MOS transistor and the second resistor is electrically coupled with the first input node of the comparator.

10. The thermal sensor of claim 9, further comprising:

a fourth MOS transistor electrically coupled with a power source voltage;

a fifth MOS transistor electrically coupled with the third MOS transistor in series, wherein a fourth node is between the fourth and fifty MOS transistors;

a third resistor electrically coupled between the fourth node and the first node; and

a fourth resistor electrically coupled between the fourth node and the second node.

11. The thermal sensor of claim 10, wherein the fifth MOS transistor is operable in a sub-threshold region during a sensing operation of the thermal sensor.

12. The thermal sensor of claim 9, wherein the current minor comprises a second comparator.

13. The thermal sensor of claim 12, wherein a first input of the second comparator is connected to the first node, and a second input of the second comparator is connected to the second node.

14. A thermal sensor comprising:

a comparator having a first input node and a second input node;

a reference voltage generator electrically coupled with the first input node of the comparator; and

a proportional to absolute temperature (PTAT) sensing circuit electrically coupled with the second input node of the comparator, wherein the temperature sensing circuit comprises;

a current mirror;

a first metal-oxide-semiconductor (MOS) transistor electrically coupled between the current mirror and ground, wherein a first node is between the first MOS transistor and the current mirror;

a first resistor electrically coupled with the current mirror, wherein a second node is between the first resistor and the current mirror;

a second MOS transistor electrically coupled with the first resistor in series, wherein the second MOS transistor and the first resistor are electrically coupled with the first MOS transistor in a parallel fashion; and

a second current mirror coupled to the first node, wherein the second current mirror is between the current mirror and the comparator.

15. The thermal sensor of claim 14, wherein the first MOS transistor and the second MOS transistor are each configured to operate in a sub-threshold region.

16. The thermal sensor of claim 14, wherein the current minor comprises an amplifier.

17. The thermal sensor of claim 16, wherein the amplifier is configured to equalize a voltage level at the first node and a voltage level at the second node.

18. The thermal sensor of claim 16, wherein the amplifier is configured to equalize a current through the first MOS transistor and a current through the second MOS transistor.

19. The thermal sensor of claim 14, wherein the current minor comprises a second comparator.

20. The thermal sensor of claim 19, wherein a first input of the second comparator is connected to the first node, and a second input of the second comparator is connected to the second node.