Battery monitoring system for an implantable medical device
First Claim
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1. An implantable medical device comprising:
- a therapy delivery device that is adapted to deliver therapy to an organ of a patient;
a controller that controls the delivery of therapy to the organ of the patient;
a CFx battery that supplies power to the therapy delivery device wherein the battery has an output characteristic with a substantially non-decreasing output voltage for a first period of time followed by a declining voltage as the battery approaches end-of-life;
a battery monitoring circuit, that samples the output voltage of the CFx battery and periodically provides sampled output voltage signals indicative thereof to the controller, wherein the controller determines a predicted end-of-life point of the battery based upon the sampled output voltage signals and wherein the controller monitors the sampled output voltage signals and determines when the sampled voltage signals are indicative of the predictive end-of-life point of the battery.
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Abstract
An implantable cardiac device, such as a pacemaker, provided with a carbon monofluoride (CFx) battery. The CFx battery enables replacement of the typical voltage tripler with a voltage doubler and eliminates the need for a bulky decoupling capacitor. The device includes a precision A/D and voltage monitor to enable more accurate prediction of impending battery end-of-life. Several methods of accurately determining a pending end-of-life of a battery with a flat voltage output throughout discharge, such as a CFx battery, are provided.
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Citations
38 Claims
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1. An implantable medical device comprising:
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a therapy delivery device that is adapted to deliver therapy to an organ of a patient;
a controller that controls the delivery of therapy to the organ of the patient;
a CFx battery that supplies power to the therapy delivery device wherein the battery has an output characteristic with a substantially non-decreasing output voltage for a first period of time followed by a declining voltage as the battery approaches end-of-life;
a battery monitoring circuit, that samples the output voltage of the CFx battery and periodically provides sampled output voltage signals indicative thereof to the controller, wherein the controller determines a predicted end-of-life point of the battery based upon the sampled output voltage signals and wherein the controller monitors the sampled output voltage signals and determines when the sampled voltage signals are indicative of the predictive end-of-life point of the battery. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
a band gap reference device coupled to the battery that provides a reference voltage that is substantially temperature independent and substantially voltage independent; and
an A/D converter that receives the reference voltage and also receives the output voltage from the battery, wherein the A/D converter sends a digital signal to the controller indicative of the ratio between the output voltage from the battery and the reference voltage.
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9. The device of claim 8, wherein the A/D converter is a 12 bit A/D converter that provides a digital word to the controller that has a resolution of approximately 1 millivolt.
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10. The device of claim 1, wherein the controller periodically receives a plurality of signals from the battery monitoring circuit and wherein the controller normalizes the periodically received values so as to reduce the effect of temporary variations in the output voltage of the battery.
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11. The device of claim 10, wherein the controller averages each received sampled output voltage signal with a pre-selected number of previous sampled output voltage values to obtain a periodic value for evaluation of whether the periodic value is indicative of the predictive end-of-life of the battery.
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12. The device of claim 11, wherein the battery monitoring circuit provides the sampled output voltage signals on a daily basis.
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13. The device of claim 1, wherein the controller sets a flag to indicate that the end-of-life of the battery has been reached such that on subsequent review of the device by a treating medical professional, the treating medical professional is advised of the need to replace the battery in the implantable device.
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14. The device of claim 1, wherein the therapy delivery device comprises at least one lead adapted to be implanted adjacent the heart of the patient so as to provide electrical stimulation to the heart.
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15. The device of claim 1, wherein the controller senses the delivery of therapy by the therapy delivery device and further implements a fuel gauge routine that models battery energy output corresponding to the delivery of therapy and correlates the modeled battery energy output with the sampled voltage signals to determine whether the battery has reached the predicted end-of-life point.
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16. An implantable cardiac stimulation device comprising:
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at least one lead adapted to be implanted adjacent the heart so as to provide therapeutic stimulation to the heart;
a therapeutic stimulation circuit that develops electrical stimulation waveforms to be delivered via the at least one lead to the heart;
a controller that controls the delivery of therapeutic electrical stimulation to the heart of the patient;
a CFx battery that provides power to the implantable cardiac stimulation device wherein the battery has an output characteristic with a substantially non-decreasing output voltage for a first period of time followed by a declining voltage as the battery approaches end-of-life;
a battery monitoring circuit that samples the output voltage of the CFx battery and periodically provides sampled output voltage signals indicative thereof to the controller, wherein the controller determines a beginning-of-life voltage value and a predicted end-of-life point of the CFx battery based at least in part upon the beginning-of-life voltage value and wherein the controller monitors the sampled output voltage signals and determines when the sampled voltage signals are indicative of the predictive end-of-life point of the CFx battery. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
a band gap reference device coupled to the battery that provides a reference voltage that is substantially temperature independent and substantially voltage independent; and
an A/D converter that receives the reference voltage and also receives the output voltage from the battery, wherein the A/D converter sends a digital signal to the controller indicative of the difference between the output voltage from the battery and the reference voltage.
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25. The device of claim 24, wherein the A/D converter is a 12 bit A/D converter that provides a digital word to the controller that has a resolution of approximately 1 millivolt.
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26. The device of claim 16, wherein the controller periodically receives a plurality of signals from the battery monitoring circuit and wherein the controller normalizes the periodically received values so as to reduce the effect of temporary variations in the output voltage of the CFx battery.
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27. An implantable cardiac stimulation device comprising:
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means for delivering therapy to the heart of a patient;
means for controlling the delivery of therapy to the heart of the patient;
means for supplying power to the implantable cardiac stimulation device wherein the means provides a relatively non-decreasing output voltage over a normal useful life and then transitions into an end-of-life state wherein the output voltage declines from the relatively non-decreasing output voltage;
means for monitoring the output characteristics of the battery, wherein the monitoring means periodically samples an output characteristic of the battery and provides an output signal indicative thereof, wherein the means for controlling receives the output signals and uses the output signals to (i) determine a predicted end-of-life point of the means for supplying power based on a beginning-of-life voltage value and (ii) determining whether the output signals are indicative of the means for supplying power having reached the predicted end-of-life point based on the beginning-of-life voltage value. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38)
a band gap reference device coupled to the battery that provides a reference voltage that is substantially temperature independent and substantially voltage independent; and
an A/D converter that receives the reference voltage and also receives the output voltage from the battery, wherein the A/D converter sends a digital signal to the control means indicative of the difference between the output voltage from the battery and the reference voltage.
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36. The device of claim 27, wherein the control means develops a normalized battery voltage signal corresponding to each of the output signals wherein the normalized battery voltage signal is processed so as to reduce the effect of temporary variations in the output voltage in the means for supplying power.
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37. The device of claim 36, wherein the control means averages each receives sampled output signals with a pre-selected number of previous sampled output signals to obtain a periodic value for evaluation of whether the periodic value is indicative of the predicted end-of-life of the means for supplying power.
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38. The device of claim 27, wherein the therapy is antitachycardia pacing.
Specification