Temperature sensor for image sensors

Patent metadata

Field	Value
Publication number	US-9234804-B2
Application number	US-201113339868-A
Country	US
Kind code	B2
Filing date	Dec 29, 2011
Priority date	Dec 29, 2011
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

An integrated temperature sensor provides an output current proportional to temperature rising from a zero value at a selectable reference temperature. The reference temperature can be selected by varying resistive values in the sensor's circuit. The temperature sensor can be manufactured at low cost and fully integrated on a chip using CMOS technology, and may be used for low-power applications.

First claim

What is claimed is:

1. A temperature sensor, comprising:
a first output transistor having first and second conduction terminals, the first conduction terminal coupled to a first voltage supply so that the first output transistor is configured to generate a first current proportional to absolute temperature from the second conduction terminal;
a current source coupled to the second conduction terminal and configured to draw a constant reference current from the second conduction terminal; and
an output terminal coupled to the second conduction terminal and configured to output an output current proportional to the absolute temperature for temperatures in excess of a first reference temperature;
wherein the value of the constant reference current determines a zero-crossing value of the output current.

2. The circuit of claim 1 , wherein the zero-crossing value of the output current is at the first reference temperature.

3. The circuit of claim 1 , further comprising a first resistive value in a temperature-sensing circuit coupled to the first output transistor and a second resistive value in the current source that adjust the zero-crossing value to be at a second reference temperature.

4. The circuit of claim 1 , wherein the constant reference current is independent of temperature of the temperature-sensing circuit.

5. The circuit of claim 1 , wherein the constant reference current varies less than about 5 microamps over a temperature range of about 200 Celsius for the temperature-sensing circuit.

6. The circuit of claim 1 , wherein the zero-crossing value corresponds to a selected reference temperature.

7. The circuit of claim 1 , further comprising a temperature-sensing circuit wherein a control terminal of the first output transistor is coupled to the temperature-sensing circuit.

8. The circuit of claim 7 , wherein the temperature-sensing circuit comprises:
a first circuit branch configured to couple between a first voltage supply and a second voltage supply;
a second transistor of a first type in the first circuit branch;
a third transistor of a second type coupled in series with the second transistor;
a first bipolar junction transistor coupled in series with the third transistor;
a second circuit branch configured to couple between the first voltage supply and the second voltage supply;
a fourth transistor of the first type in the second circuit branch and configured in a current mirror relationship with the second transistor;
a fifth transistor of the second type in series with the fourth transistor and configured in a current mirror relationship with the third transistor;
a resistor in series with the fifth transistor; and
a second bipolar junction transistor coupled in series with the resistor and configured in a current mirror relationship with the first bipolar junction transistor.

9. The circuit of claim 8 , wherein a control terminal of the second transistor is coupled to a control terminal of the first output transistor, and the conduction terminal of the first output transistor is coupled to the first supply voltage.

10. The circuit of claim 8 , wherein a control terminal of the fifth transistor is coupled to provide a temperature-dependent current in the current source.

11. The circuit of claim 8 , wherein the second bipolar junction transistor is configured to exhibit a higher current density flow than the first bipolar junction transistor.

12. The circuit of claim 11 , wherein the higher current density flow is by a factor of about 8.

13. The circuit of claim 1 , wherein the current source is configured to combine a second current proportional to absolute temperature with a temperature-dependent current to provide the constant reference current.

14. The circuit of claim 13 , wherein the current source comprises:
a first circuit branch configured to couple between a first voltage supply and a second voltage supply;
a second transistor of a first type in the first circuit branch;
a third transistor of a second type coupled in series with the second transistor;
a resistor in series with the third transistor;
a second circuit branch configured to couple between the first voltage supply and the second voltage supply;
a fourth transistor of the first type in the second circuit branch and configured in a current mirror relationship with the second transistor; and
a fifth transistor of the second type in series with the fourth transistor.

15. The circuit of claim 13 , wherein the second current proportional to absolute temperature is added to the second circuit branch by a sixth transistor having a control terminal coupled to a first output of a temperature-sensing circuit, and the temperature-dependent current is provided in the first circuit branch by the third transistor having a control terminal coupled to a second output of the temperature-sensing circuit.

16. The circuit of claim 15 , wherein the temperature-dependent current has an opposite dependence on temperature than the second current proportional to absolute temperature.

17. The circuit of claim 16 , further comprising a seventh transistor of the second type coupled in series with the first output and configured in a current mirror relationship with the fifth transistor.

18. A method for providing an output current proportional to temperature, the method comprising:
supplying a first current proportional to absolute temperature to a node of a temperature sensor;
removing a constant reference current from the node; and
outputting a second current proportional to absolute temperature from the node when temperature exceeds a first reference temperature;
wherein the value of the constant reference current determines a zero-crossing value of the second current.

19. The method of claim 18 , wherein the constant reference current is selected to determine a zero-crossing value of the second current.

20. The method of claim 18 , wherein the supplying comprises providing a first control signal from a first output of a temperature-sensing circuit to a control terminal of a first transistor to control the first transistor to supply the first current proportional to absolute temperature.

21. The method of claim 20 , wherein the removing comprises providing a second control signal from a current source to control terminal of a second transistor coupled in series with the first transistor.

22. The method of claim 21 , further comprising:
providing a third control signal to the current source from a second output of the temperature-sensing circuit; and
combining, in the current source, the second current proportional to absolute temperature with a temperature-dependent current to provide the constant reference current.

23. The method of claim 22 , wherein the temperature-dependent current has an opposite temperature dependence than the second current proportional to absolute temperature.

24. The method of claim 20 , wherein a zero-crossing value of the output current is determined by a first resistive value in the temperature-sensing circuit and a second resistive value in the current source.

25. The method of claim 20 , further comprising:
flowing a second current in a first circuit branch of the temperature-sensing circuit, wherein the first circuit branch comprises:
a second transistor of a first type;
a third transistor of a second type coupled in series with the second transistor; and
a first bipolar junction transist

Assignees

• Englasyam Mukesh Rao
• Desprez-Le-Goarant Yann
• St Microelectronics Asia

Inventors

• Englasyam Mukesh Rao
• Desprez-Le-Goarant Yann

Classifications

• G01K7/015 Primary

  using microstructures, e.g. made of silicon · CPC title