Temperature Sensor for a Leadless Cardiac Pacemaker

• US 20130261497A1
• Filed: 05/23/2013
• Published: 10/03/2013
• Est. Priority Date: 10/12/2010
• Status: Active Grant

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Inventors: Pertijs, Michiel, Carroll, Kenneth J.
• Granted Patent: US 9,060,692 B2
• Time in Patent Office: Days
• US Class Current: 600/549
• CPC Class Codes: A61B 2562/0271 Thermal or temperature sensors
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 5/6876 Blood vessel
• CPC Class Codes: A61N 1/36514 controlled by a physiological quantity other than heart potential, e.g. blood pressure controlled by two or more physical parameters A61N1/36585
• CPC Class Codes: A61N 1/3655 controlled by body or blood temperature
• CPC Class Codes: A61N 1/3756 Casings with electrodes thereon, e.g. leadless stimulators

Abstract

A leadless cardiac pacemaker comprises a hermetic housing, a power source disposed in the housing, at least two electrodes supported by the housing, a semiconductor temperature sensor disposed in the housing, and a controller disposed in the housing and configured to deliver energy from the power source to the electrodes to stimulate the heart based upon temperature information from the temperature sensor. In some embodiments, the sensor can be configured to sense temperature information within a predetermined range of less than 20 degrees C. The temperature sensor can be disposed in the housing but not bonded to the housing.

Claims

1. A semiconductor temperature sensor, comprising:

at least one bipolar transistor configured to generate;

a complimentary-to-absolute-temperature (CTAT) signal derived from a base-emitter voltage of the at least one bipolar transistor;

first and second proportional-to-absolute-temperature (PTAT) signals derived from the at least one bipolar transistor, the first PTAT signal being equal to the CTAT signal at a first temperature, the second PTAT signal being equal to the CTAT signal at a second temperature;

an analog-to-digital converter (ADC) configured to covert the CTAT signal and the first and second PTAT signals into a digital temperature output signal; and

a controller configured to scale the digital temperature output signal to represent a preferred temperature scale.

2. The semiconductor temperature sensor of claim 1 wherein the preferred temperature scale comprises a Celsius scale.

3. The semiconductor temperature sensor of claim 1 wherein the preferred temperature scale comprises a Fahrenheit scale.

4. The semiconductor temperature sensor of claim 1 wherein the preferred temperature scale comprises a Kelvin scale.

5. The semiconductor temperature sensor of claim 1 wherein the first and second PTAT signals are derived from a single bipolar transistor to which first and second bias currents are successively applied.

6. The semiconductor temperature sensor of claim 1 wherein the at least one bipolar transistor comprises a first bipolar transistor and a second bipolar transistor, wherein the first and second PTAT signals are derived from a difference in base-emitter voltages between the first and second bipolar transistors.

7. The semiconductor temperature sensor of claim 1 wherein the ADC comprises a charge-balancing ADC.

8. The semiconductor temperature sensor of claim 7 wherein the charge-balancing ADC is configured to balance a charge accumulated proportional to the CTAT signal by negative feedback with a charge proportional to the first or second PTAT signals.

9. The semiconductor temperature sensor of claim 8 wherein an intermediate signal in the charge-balancing ADC is configured to determine which of the first or second PTAT signals is used in the negative feedback path, such that a charge provided by the negative feedback path equals a charge provided by the CTAT signal.

10. The semiconductor temperature sensor of claim 9 wherein an average value of the intermediate signal is equal to a relative value of the CTAT signal with respect to the first and second PTAT signals.

11. A method of measuring temperature with a semiconductor temperature sensor, comprising:

deriving a complimentary-to-absolute-temperature (CTAT) signal from a base-emitter voltage of at least one bipolar transistor;

deriving first and second proportional-to-absolute-temperature (PTAT) signals from the at least one bipolar transistor, wherein the first PTAT signal is approximately equal to the CTAT signal at a first temperature, wherein the second PTAT signal is approximately equal to the CTAT signal at a second temperature;

converting the CTAT signal and the first and second PTAT signals into a digital temperature output signal with an analog-to-digital converter (ADC); and

scaling the digital temperature output signal to represent a preferred temperature scale.

12. The method of claim 11 further comprising calibrating the semiconductor temperature sensor at a first temperature to establish an initial temperature error.

13. The method of claim 11 further comprising correcting a bias current used to generate the CTAT signal to bring an initial temperature error within range of the ADC.

14. A leadless cardiac pacemaker comprising:

a hermetic housing configured to be implanted in a chamber of a human heart;

a power source disposed in the housing;

at least two electrodes supported by the housing;

a semiconductor temperature sensor disposed in the housing, comprising;

at least one bipolar transistor configured to generate a complimentary-to-absolute-temperature (CTAT) signal derived from a base-emitter voltage of at least one bipolar transistor, and first and second proportional-to-absolute-temperature (PTAT) signals derived from the at least one bipolar transistor, the first PTAT signal being equal to the CTAT signal at a first temperature, the second PTAT signal being equal to the CTAT signal at a second temperature;

an analog-to-digital converter (ADC) configured to covert the CTAT signal and the first and second PTAT signals into a digital temperature output signal;

a controller disposed in the housing and configured to deliver energy from the power source to the electrodes to stimulate the heart based on the digital temperature output signal from the semiconductor temperature sensor.

15. The leadless cardiac pacemaker of claim 14 further comprising a fixation helix adapted to attach the hermetic housing to the heart.

16. The leadless cardiac pacemaker of claim 14 wherein the semiconductor temperature sensor is not bonded to the housing.

17. A leadless cardiac pacemaker comprising:

a hermetic housing configured to be implanted in a chamber of a human heart;

a switched-bias power source disposed in the housing;

at least two electrodes supported by the housing;

a semiconductor temperature sensor comprising;

at least one bipolar transistor configured to generate a complimentary-to-absolute-temperature (CTAT) signal derived from a base-emitter voltage of at least one bipolar transistor, and first and second proportional-to-absolute-temperature (PTAT) signals derived from the at least one bipolar transistor, the first PTAT signal being generated by operating the at least one bipolar transistor at a first pair of current densities, the second PTAT signal being generated by operating the at least one bipolar transistor at a second pair of current densities, wherein a first ratio of the first pair of current densities differs from a second ratio of the second pair of current densities;

an analog-to-digital converter (ADC) configured to covert the CTAT signal and the first and second PTAT signals into a digital temperature output signal; and

a controller disposed in the housing and configured to deliver energy from the power source to the electrodes to stimulate the heart based upon the digital temperature output signal from the semiconductor temperature sensor.

18. The leadless cardiac pacemaker of claim 17 further comprising a fixation helix adapted to attach the hermetic housing to the heart.

19. The leadless cardiac pacemaker of claim 17 wherein the semiconductor temperature sensor is not bonded to the housing.

20. A leadless cardiac pacemaker comprising:

a hermetic housing configured to be disposed in a chamber of a human heart;

a power source disposed in the housing;

at least two electrodes supported by the housing;

a semiconductor temperature sensor disposed in the housing, the semiconductor temperature sensor being configured to sense temperature information within a predetermined range of less than 20 degrees C.; and

a controller disposed in the housing and configured to deliver energy from the power source to the electrodes to stimulate the heart based upon temperature information from the temperature sensor.

21. The leadless cardiac pacemaker of claim 20 wherein the semiconductor temperature sensor is configured to sense temperature information within a predetermined range of less than 10 degrees C.

22. The leadless cardiac pacemaker of claim 20 wherein the semiconductor temperature sensor is configured to sense temperature information within a predetermined range of 36 to 42 degrees C.

23. The leadless cardiac pacemaker of claim 20 wherein the controller comprises an ASIC and the semiconductor temperature sensor is incorporated into the ASIC.

24. The leadless cardiac pacemaker of claim 20 wherein the semiconductor temperature sensor is configured to sense the temperature of blood surrounding the leadless cardiac pacemaker.

25. The leadless cardiac pacemaker of claim 20 wherein the semiconductor temperature sensor is not bonded to the housing.

26. The leadless cardiac pacemaker of claim 20 wherein the semiconductor temperature sensor includes a low-resolution analog-to-digital converter adapted to consume less than 100 nA of current at greater than 0.1 temperature samples per second.