PROGRAMMABLE TEMPERATURE SENSING CIRCUIT FOR AN INTEGRATED CIRCUIT

• US 20120242398A1
• Filed: 03/21/2011
• Published: 09/27/2012
• Est. Priority Date: 03/21/2011
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Olmos, Alfredo, Pietri, Stefano, Coimbra, Ricardo P.
• Granted Patent: US 8,432,214 B2
• Time in Patent Office: Days
• US Class Current: 327/512
• CPC Class Codes: G01K 7/01 using semiconducting elements having PN junctions G01K7/02, G01K7/16, G01K7/30 take precedence

Abstract

A programmable temperature sensing circuit includes a comparator, first and second CTAT sensing elements, first and second PTAT reference circuits, and a selection circuit. When a selection signal is a first logic state, an output terminal of the first PTAT reference circuit is coupled to the second CTAT temperature sensing element for providing a first threshold voltage to the second input of the comparator. When the selection signal is a second logic state different from the first logic state, a series-connection of the first PTAT reference circuit and the second PTAT reference circuit are coupled to the second CTAT temperature sensing element for providing a second threshold voltage to the second input of the comparator. The comparator provides an output voltage indication when a voltage provided by the first CTAT sensing element compares favorably with the selected one of the first or second threshold voltages.

Claims

1. A temperature sensing circuit comprising:

a comparator having a first input, a second input, and an output;

a first temperature sensing element having a first terminal coupled to the first input of the comparator, and a second terminal, the first temperature sensing element for providing a first complementary to absolute temperature (CTAT) voltage;

a second temperature sensing element having a first terminal coupled to the second input of the comparator, and a second terminal, the second temperature sensing element for providing a second CTAT voltage;

a first reference circuit having an output terminal for providing a first proportional to absolute temperature (PTAT) voltage;

a second reference circuit having an output terminal for providing a second PTAT voltage; and

a selection circuit for selectively coupling the output terminals of the first reference voltage circuit and the second reference voltage circuit to the second terminal of the second temperature sensing element in response to a selection signal,

wherein when the selection signal is a first logic state, the output terminal of the first reference circuit is coupled to the second terminal of the second temperature sensing element for providing a first threshold voltage to the second input of the comparator, and when the selection signal is a second logic state different from the first logic state, a series connection of the first reference circuit and the second reference circuit are coupled to the second terminal of second temperature sensing element for providing a second threshold voltage to the second input of the comparator.

2. The temperature sensing circuit of claim 1, wherein the first temperature sensing element comprises at least one diode.

3. The temperature sensing circuit of claim 1, wherein the second temperature sensing element comprises a diode.

4. The temperature sensing circuit of claim 1, further comprising a current mirror circuit coupled to the first and second sensing circuits and the first and second reference circuits.

5. The temperature sensing circuit of claim 1, wherein the first reference circuit comprises:

a first transistor having a control electrode and a first current electrode coupled together, and a second current electrode; and

a second transistor having a control electrode coupled to the control electrode of the first transistor, a first current electrode coupled to the second current electrode of the first transistor, and a second current electrode coupled to a power supply voltage terminal.

6. The temperature sensing circuit of claim 5, wherein the second reference circuit comprises:

a third transistor having a control electrode and a first current electrode coupled together, and a second current electrode; and

a fourth transistor having a control electrode coupled to the control electrode of the first transistor, a first current electrode coupled to the second current electrode of the third transistor, and a second current electrode.

7. The temperature sensing circuit of claim 6, wherein the selection circuit comprises:

a first switch having a first terminal coupled to the first current electrode of the second transistor, and a second terminal coupled to the second current electrode of the fourth transistor;

a second switch having a first terminal coupled to the first current electrode of the fourth transistor, and a second terminal coupled to the second terminal of the second temperature sensing element, wherein the first and second switches are responsive to the selection signal; and

a third switch having a first terminal coupled to the second terminal of the second temperature sensing element, and a second terminal coupled to the first current electrode of the second transistor, wherein the third switch is responsive to a logical complement of the selection signal.

8. The temperature sensing circuit of claim 1, further comprising a trimming circuit for adjusting the first and second threshold voltages in response to a trim signal, the trimming circuit coupled between a power supply voltage terminal and the second terminal of the second temperature sensing element.

9. The temperature sensing circuit of claim 8, wherein the trimming circuit comprises a plurality of parallel-connected switchable current sources.

10. A temperature sensing circuit comprising:

a comparator having a first input terminal, a second input terminal, and an output terminal;

a first complementary to absolute temperature (CTAT) sensing element having a first terminal coupled to the first input of the comparator, and a second terminal, the first temperature sensing element for providing a first CTAT voltage;

a second CTAT sensing element having a first terminal coupled to the second input of the comparator, and a second terminal, the second temperature sensing element for providing a second CTAT voltage;

a first proportional to absolute temperature (PTAT) reference circuit having an output terminal for providing a first PTAT voltage;

a second PTAT reference circuit having an output terminal for providing a second PTAT voltage; and

a selection circuit for selectively coupling the output terminals of the first PTAT reference circuit and the second PTAT reference circuit to the second terminal of the second CTAT sensing element in response to a selection signal,

wherein, in response to the selection signal being a first logic state, a first threshold voltage is provided to the second input terminal of the comparator, the first threshold voltage comprising a combination of the second CTAT voltage and the first PTAT voltage, and in response to the selection signal being a second logic state different from the first logic state, a second threshold voltage is provided to the second input terminal of the comparator, the second threshold voltage comprising a combination of the second CTAT voltage, the first PTAT voltage, and the second PTAT voltage.

11. The temperature sensing circuit of claim 10, wherein the first CTAT sensing element comprises at least one diode.

12. The temperature sensing circuit of claim 10, wherein the first CTAT sensing element comprises two series-connected diodes.

13. The temperature sensing circuit of claim 10, wherein the first PTAT reference circuit comprises:

a first transistor having a first current electrode and a control electrode coupled together, and a second current electrode; and

a second transistor having a first current electrode coupled to the second current electrode of the first transistor, a control electrode coupled to the control electrode of the first transistor, and a second current electrode.

14. The temperature sensing circuit of claim 10, further comprising a current mirror circuit for providing a current source for each of the first and second CTAT sensing elements and the first and second PTAT reference circuits.

15. The temperature sensing circuit of claim 10, further comprising a trimming circuit for adjusting the first and second threshold voltages in response to a trim signal, the trimming circuit coupled between a power supply terminal and the second terminal of the second CTAT sensing element.

16. The temperature sensing circuit of claim 15, wherein the trimming circuit comprises a plurality of parallel-connected switchable current sources.

17. The temperature sensing circuit of claim 10, wherein the first threshold voltage is a high temperature threshold voltage and the second threshold voltage is a low temperature threshold voltage.

18. A temperature sensing circuit comprising:

a comparator having a first input terminal, a second input terminal, and an output terminal;

a first current source having a first terminal coupled to a first power supply voltage terminal, and a second terminal coupled to the first input terminal of the comparator;

a first complementary to absolute temperature (CTAT) sensing element having a first terminal coupled to the first input of the comparator, and a second terminal coupled to a second power supply voltage terminal, the first temperature sensing element for providing a first CTAT voltage;

a second current source having a first terminal coupled to the first power supply voltage terminal, and a second terminal coupled to the second input terminal of the comparator;

a second CTAT sensing element having a first terminal coupled to the second input of the comparator, and a second terminal, the second temperature sensing element for providing a second CTAT voltage;

a third current source having a first terminal coupled to the first power supply voltage terminal, and a second terminal;

a first proportional to absolute temperature (PTAT) reference circuit having a first terminal coupled to the second terminal of the third current source, a second terminal for providing a first PTAT voltage, and a third terminal coupled to the second power supply voltage terminal;

a fourth current source having a first terminal coupled to the first power supply voltage terminal, and a second terminal;

a second PTAT reference circuit having a first terminal coupled to the second terminal of the fourth current source, a second terminal for providing a second PTAT voltage, and a third terminal; and

a selection circuit comprising;

a first switch having a first terminal coupled to the second terminal of the first PTAT reference circuit, a second terminal for receiving a first selection signal, and a third terminal coupled to the third terminal of the second PTAT reference circuit;

a second switch having a first terminal coupled to the second terminal of the second PTAT reference circuit, a second terminal for receiving the first selection signal, and a third terminal coupled to the second terminal of the second CTAT sensing element; and

a third switch having a first terminal coupled to the second terminal of the second CTAT sensing element, a second terminal for receiving a second selection signal, and a third terminal coupled to the second terminal of the first PTAT reference circuit, wherein the second selection signal is a logical complement of the first selection signal.

19. The temperature sensing circuit of claim 18, wherein the first and second CTAT sensing elements each comprise a diode.

20. The temperature sensing circuit of claim 18, wherein the first and second PTAT reference circuits each comprise:

a first transistor having a first current electrode and a control electrode coupled together, and a second current electrode; and

a second transistor having a first current electrode coupled to the second current electrode of the first transistor, a control electrode coupled to the control electrode of the first transistor, and a second current electrode.