DIGITAL OUTPUT TEMPERATURE SENSOR

• US 20100124251A1
• Filed: 11/18/2008
• Published: 05/20/2010
• Est. Priority Date: 11/18/2008
• Status: Active Grant

• Current Assignee: Toshiba America Electronic Components Incorporated (Toshiba Corporation)
• Original Assignee: Toshiba America Electronic Components Incorporated (Toshiba Corporation)
• Inventors: Welch, James R., Peterson, Luverne R.
• Granted Patent: US 8,262,286 B2
• Time in Patent Office: Days
• US Class Current: 374/171
• CPC Class Codes: G01K 7/01 using semiconducting elements having PN junctions G01K7/02, G01K7/16, G01K7/30 take precedence

Abstract

A temperature sensor generates a digital output signal representative of the absolute temperature of the sensor. The sensor includes a first circuit configured to generate a complementary to absolute temperature (CTAT) voltage signal and a second circuit configured to generate a proportional to absolute temperature (PTAT) current signal. A comparator receives the CTAT and PTAT signals and generates a comparison signal based on a comparison between the signals. A converter circuit receives the comparison signal and generates a digital output signal based on the comparison signal. The digital output signal is representative of the temperature of the sensor.

Claims

1. A digital output temperature sensor comprising:

a first circuit configured to generate a first signal, the first signal varying complementary to a temperature of the sensor;

a second circuit configured to generate a second signal, the second signal varying proportionally to the temperature of the sensor;

a comparator operatively associated with the first and second circuits and configured to receive the first and second signals and generate a comparison signal based on a comparison between the first and second signals; and

,

a converter circuit operatively associated with the comparator and configured to receive the comparison signal and generate a digital output signal based on the comparison signal, the digital output signal being representative of the temperature of the sensor.

2. The digital output temperature sensor of claim 1 wherein:

the first circuit is a reference voltage generator circuit including a pair of stacked diodes configured to generate a complementary to absolute temperature (CTAT) voltage signal as said first signal;

the second circuit is configured to generate a proportional to absolute temperature (PTAT) current signal as said second signal; and

,

the converter circuit is configured to receive the comparison signal and generate the digital output signal proportional to an absolute temperature of the sensor.

3. The digital output temperature sensor of claim 2 wherein the pair of stacked diodes is a pair of grounded emitter PNP transistors.

4. The digital output temperature sensor of claim 1 wherein:

the first circuit is a reference voltage generator circuit including a pair of stacked diodes configured to generate a complementary to absolute temperature (CTAT) voltage signal as said first signal;

the second circuit is configured to generate a proportional to absolute temperature (PTAT) current signal as said second signal, the second circuit including;

i) a PTAT current control reference voltage generating circuit configured to generate a PTAT current control reference voltage signal;

ii) a digital to analog converter circuit including a plurality of current sources receiving the PTAT current control reference voltage signal and being selectively switchable between a conductive state and a non-conductive state, wherein each of the plurality of current sources in the conductive state sources a partial current;

iii) a current summing junction summing each of the plurality of partial currents as said PTAT current signal; and

iv) a resistor between the current summing junction and a ground, the resistor being configured to convert the PTAT current signal to a PTAT voltage signal for use by said comparator; and

,

the converter circuit is configured to receive the comparison signal and generate the digital output signal proportional to an absolute temperature of the sensor.

5. The digital output temperature sensor of claim 4 wherein:

each of the plurality of current sources is configured to generate PTAT partial currents, the plurality of current sources including current source transistors having varied lengths for adjusting a linearity of the digital to analog converter circuit over a range of temperatures of the sensor; and

,

the current summing junction is configured to sum each of the plurality of partial PTAT currents as said PTAT current signal.

6. The digital output temperature sensor of claim 1 wherein:

the first circuit is configured to generate a complementary to absolute temperature (CTAT) voltage signal as said first signal;

the second circuit is configured to generate a proportional to absolute temperature (PTAT) current signal as said second signal; and

,

the converter circuit is configured to receive the comparison signal and generate the digital output signal proportional to an absolute temperature of the sensor, the converter circuit including a counter circuit configured to count clock pulses of an associated clock signal as said digital output signal in response to said comparison signal.

7. The digital output temperature sensor of claim 1 wherein:

the first circuit is configured to generate a complementary to absolute temperature (CTAT) voltage signal as said first signal, the first circuit including a reference voltage generator circuit including a pair of grounded emitter PNP transistors;

the second circuit is configured to generate a proportional to absolute temperature (PTAT) current signal as said second signal, the second circuit including;

i) a PTAT current control reference voltage generating circuit configured to generate a PTAT current control reference voltage signal;

ii) a digital to analog converter circuit including a plurality of current sources receiving the PTAT current control reference voltage signal and being selectively switchable between a conductive state and a non-conductive state, wherein each of the plurality of current sources in the conductive state sources a partial current, the plurality of current sources including current source transistors having varied lengths for adjusting a linearity of the digital to analog converter circuit over a range of temperatures of the sensor;

iii) a current summing junction summing each of the plurality of partial currents as said PTAT current signal; and

iv) a resistor between the current summing junction and a ground, the resistor being configured to convert the PTAT current signal to a PTAT voltage signal for use by said comparator; and

,

the converter circuit is configured to receive the comparison signal and generate the digital output signal proportional to an absolute temperature of the sensor, the converter circuit including a counter circuit configured to count clock pulses of an associated clock signal as said digital output signal in response to said comparison signal.

8. The digital output temperature sensor of claim 1:

wherein;

the first circuit is configured to generate a complementary to absolute temperature (CTAT) voltage signal as said first signal;

the second circuit is configured to generate a proportional to absolute temperature (PTAT) current signal as said second signal; and

, the converter circuit is configured to receive the comparison signal and generate the digital output signal proportional to an absolute temperature of the sensor; and

,

further including an offset adjustment circuit operatively associated with the second circuit and the comparator circuit, the offset adjustment circuit being configured to selectively generate an offset current signal and being operatively coupled with the second circuit and the comparator circuit for adding the offset current signal with the PTAT current signal.

9. A digital output temperature sensor comprising:

a first circuit configured to generate a complementary to absolute temperature (CTAT) voltage signal as a first signal, the first circuit using a pair of stacked diodes to generate the first signal;

a reference circuit configured to generate a reference signal, the reference signal being substantially independent of the temperature of the sensor;

a comparator operatively associated with the first circuit and the reference circuit and configured to receive the first and reference signals and generate a comparison signal based on a comparison between the first and reference signals; and

,

a converter circuit operatively associated with the comparator and configured to receive the comparison signal and generate a digital output signal based on the comparison signal, the digital output signal being representative of the temperature of the sensor.

10. The digital output temperature sensor of claim 9 wherein the pair of stacked diodes is a pair of grounded emitter PNP transistors.

11. A method in a temperature sensor of sensing a temperature, the method comprising:

generating a first signal varying complementary to a temperature of the sensor;

generating a second signal varying proportionally to the temperature of the sensor;

generating a comparison signal based on a comparison between the first and second signals; and

,

generating a digital output signal based on the comparison signal, the digital output signal being representative of the temperature of the sensor.

12. The method of claim 11 wherein:

the generating the first signal includes generating, using a pair of stacked diodes, a complementary to absolute temperature (CTAT) voltage signal as said first signal;

the generating the second signal includes generating a proportional to absolute temperature (PTAT) current signal as said second signal; and

,

the generating the digital output signal includes generating the digital output signal proportional to an absolute temperature of the sensor.

13. The method of claim 12 wherein the generating the complementary to absolute temperature (CTAT) voltage signal includes generating the complementary to absolute temperature (CTAT) voltage signal using a pair of grounded emitter PNP transistors.

14. The method of claim 11 wherein:

the generating the first signal includes generating a complementary to absolute temperature (CTAT) voltage signal as said first signal;

the generating the second signal includes generating a proportional to absolute temperature (PTAT) current signal as said second signal by;

i) using a PTAT current control reference voltage generating circuit, generating a PTAT current control reference voltage signal;

ii) using a digital to analog converter circuit including a plurality of current sources receiving the PTAT current control reference voltage signal and being selectively switchable between a conductive state and a non-conductive state, sourcing a partial current by each of the plurality of current sources in the conductive state;

iii) using a current summing junction, summing each of the plurality of partial currents as said PTAT current signal; and

iv) using a resistor between the current summing junction and a ground, converting the PTAT current signal to a PTAT voltage signal; and

,

the generating the digital output signal includes generating the digital output signal proportional to an absolute temperature of the sensor.

15. The method of claim 14 wherein:

the generating the partial current by each of the plurality of current sources in the conductive state includes generating PTAT partial currents by each of the plurality of current sources in the conductive state by transistors having varied lengths for adjusting a linearity of the digital to analog converter circuit over a range of temperatures of the sensor; and

,

the summing each of the plurality of partial currents as said PTAT current signal using the current summing junction includes summing each of the plurality of partial PTAT currents as said PTAT current signal.

16. The method of claim 11 wherein:

the generating the first signal includes generating a complementary to absolute temperature (CTAT) voltage signal as said first signal;

the generating the second signal includes generating a proportional to absolute temperature (PTAT) current signal as said second signal; and

,

the generating the digital output signal includes generating the digital output signal proportional to an absolute temperature of the sensor by counting clock pulses of an associated clock signal using a counter circuit in response to said comparison signal.

17. The method of claim 11 wherein:

the generating the first signal includes generating a complementary to absolute temperature (CTAT) voltage signal as said first signal using a pair of grounded emitter PNP transistors;

the generating the second signal includes generating a proportional to absolute temperature (PTAT) current signal by counting clock pulses of an associated clock signal as said digital output signal in response to said comparison signal as said second signal; and

,

the generating the digital output signal includes generating the digital output signal proportional to an absolute temperature of the sensor by;

i) using a PTAT current control reference voltage generating circuit, generating a PTAT current control reference voltage signal;

ii) using a digital to analog converter circuit including a plurality of current sources receiving the PTAT current control reference voltage signal and being selectively switchable between a conductive state and a non-conductive state, sourcing a partial current by each of the plurality of current sources in the conductive state;

iii) using a current summing junction, summing each of the plurality of partial currents as said PTAT current signal; and

iv) using a resistor between the current summing junction and a ground, converting the PTAT current signal to a PTAT voltage signal, wherein the generating the PTAT partial currents by each of the plurality of current sources in the conductive state includes generating the PTAT partial currents by transistors having varied lengths for adjusting a linearity of the digital to analog converter circuit over a range of temperatures of the sensor.

18. The method of claim 11:

wherein;

the generating the first signal includes generating a complementary to absolute temperature (CTAT) voltage signal as said first signal;

the generating the second signal includes generating a proportional to absolute temperature (PTAT) current signal as said second signal; and

, the generating the digital output signal includes generating the digital output signal proportional to an absolute temperature of the sensor; and

,

further including selectively generating an offset current signal for adding the offset current signal with the PTAT current signal.

19. A method in a temperature sensor of sensing a temperature, the method comprising:

using a pair of stacked diodes, generating a complementary to absolute temperature (CTAT) voltage signal as a first signal;

generating a reference signal, the reference signal being substantially independent of the temperature of the sensor;

generating a comparison signal based on a comparison between the complementary to absolute temperature (CTAT) voltage signal and reference signals; and

,

generating a digital output signal based on the comparison signal, the digital output signal being representative of the temperature.

20. The method of claim 19 wherein the generating the complementary to absolute temperature (CTAT) voltage signal includes generating the complementary to absolute temperature (CTAT) voltage signal using a pair of grounded emitter PNP transistors.