IMPLANTABLE MEDICAL DEVICE WITH LOW POWER DELTA-SIGMA ANALOG-TO-DIGITAL CONVERTER
First Claim
1. An implantable medical device comprising:
- at least one sensor that generates an analog input signal;
at least one delta-sigma analog-to-digital converter (ADC) that converts the analog input signal to a digital signal, the delta-sigma ADC comprising;
an integrator that produces an integrated difference between the analog input signal and a reconstruction of the analog input signal;
a quantizer that produces a control signal based on the integrated differencean up/down counter that adjusts a digital value according to the control signal;
a digital-to-analog converter (DAC) that generates the reconstruction of the analog input signal based on the digital value of the up/down counter and provides the reconstruction of the analog input signal as negative feedback to the integrator, wherein a resolution of the quantizer is less than a resolution of the DAC; and
a compensation module that compensates for a phase shift in the negative feedback caused by the integrator and the up/down counter,wherein the device further comprises;
a processor that receives the digital signal from the delta-sigma ADC.
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Abstract
In general, this disclosure describes techniques for reducing power consumption within an implantable medical device (IMD). An IMD implanted within a patient may have finite power resources that are intended to last several years. To promote device longevity, sensing and therapy circuits of the IMD are designed to incorporate an analog-to-digital converter (ADC) that provides relatively high resolution output at a relatively low operation frequency, and does so with relatively low power consumption. An ADC designed in accordance with the techniques described herein utilizes a quantizer that has a lower resolution than a digital-to-analog converter (DAC) used for negative feedback. Such a configuration provides the benefits of higher resolution DAC feedback without having the use high oversampling ratios that result in high power consumption. Also, the techniques avoid the use of, and the associated high power consumption of, a high resolution flash ADC, within the sigma delta loop.
98 Citations
25 Claims
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1. An implantable medical device comprising:
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at least one sensor that generates an analog input signal; at least one delta-sigma analog-to-digital converter (ADC) that converts the analog input signal to a digital signal, the delta-sigma ADC comprising; an integrator that produces an integrated difference between the analog input signal and a reconstruction of the analog input signal; a quantizer that produces a control signal based on the integrated difference an up/down counter that adjusts a digital value according to the control signal; a digital-to-analog converter (DAC) that generates the reconstruction of the analog input signal based on the digital value of the up/down counter and provides the reconstruction of the analog input signal as negative feedback to the integrator, wherein a resolution of the quantizer is less than a resolution of the DAC; and a compensation module that compensates for a phase shift in the negative feedback caused by the integrator and the up/down counter, wherein the device further comprises; a processor that receives the digital signal from the delta-sigma ADC. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method comprising:
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receiving an analog input signal from at least one sensor of an implantable medical device; converting the analog input signal to a digital signal using at least one delta-sigma analog-to-digital converter (ADC), wherein converting the analog input signal to the digital signal using the at least one delta-sigma ADC comprises; producing, with an integrator, an integrated difference between the analog input signal and a reconstruction of the analog input signal, producing, with a quantizer, a control signal based on the integrated difference, adjusting a digital value of an up/down counter according to the control signal, generating the reconstruction of the analog input signal based the digital value of the up/down counter using a digital-to-analog converter (DAC), wherein a resolution of the quantizer is less than a resolution of the DAC, providing the reconstruction of the analog input signal as negative feedback to the integrator, and compensating for a phase shift in the negative feedback caused by the integrator and the up/down counter, wherein the method further comprises; sending the digital signal from the delta-sigma ADC to a processor for analysis. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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17. The method of claim 11, further comprising controlling delivery of a therapy to a patient based on analysis of the digital signal from the delta-sigma ADC.
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18. The method of claim 17, wherein controlling delivery of a therapy to a patient based on analysis of the digital signal comprises:
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determining whether an intrinsic depolarization occurs within a time interval based on the digital signal from the delta-sigma ADC; and delivering the therapy to the patient based on the determination.
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19. The method of claim 11, wherein receiving an analog input signal from at least one sensor comprises receiving an analog input signal representative of a sensed physiological parameter of a patient.
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20. The method of claim 11, wherein the implantable medical device includes one of a cardiac pacemaker, a cardiac defibrillator, an electrical neurostimulator, an implantable drug delivery device, and a monitoring device.
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21. An implantable medical device comprising:
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means for generating an analog input signal; means for converting the analog input signal to a digital signal, wherein the converting means comprises; means for producing an integrated difference between the analog input signal and a reconstruction of the analog input signal, means for producing a control signal at a first resolution based on the integrated difference, means for adjusting a digital value according to the control signal, means for generating the reconstruction of the analog input signal at a second resolution based on the digital value and providing the reconstruction of the analog input signal as negative feedback to the means for producing the integrated difference, wherein the first resolution is less than the second resolution, means for compensating for a phase shift in the negative feedback caused by the means for producing the integrated difference and the means for adjusting the digital value, wherein the device further comprises; means for analyzing the digital signal from the converting means. - View Dependent Claims (22, 23, 24, 25)
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Specification