Low power A/D converter
First Claim
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1. An implantable cardiac stimulation device comprising:
- an analog chip including a sampling circuit having a first capacitor, a second capacitor, and a comparator arranged to compare a series of analog voltage signal samples on the first capacitor with a second voltage on the second capacitor, the second voltage being linearly increased or decreased to equal the sample value via first and second current sources coupled to analog control circuitry also disposed on the analog chip; and
a digital chip including digital control circuitry and a counter whose count is frozen at counts which are proportional to the voltage of the respective signal samples in response to an output from the comparator.
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Abstract
A comparator is arranged to compare a series of analog voltage signal samples on a first capacitor with a voltage on a second capacitor which is linearly increased or decreased to equal the sample value. The comparator'"'"'s single output freezes the count of the counter at counts which are proportional to the voltage of the respective samples. In this manner, analog to digital conversion can be accomplished using a single line between the analog and digital sides of a circuit, thereby reducing parasitic capacitance.
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Citations
7 Claims
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1. An implantable cardiac stimulation device comprising:
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an analog chip including a sampling circuit having a first capacitor, a second capacitor, and a comparator arranged to compare a series of analog voltage signal samples on the first capacitor with a second voltage on the second capacitor, the second voltage being linearly increased or decreased to equal the sample value via first and second current sources coupled to analog control circuitry also disposed on the analog chip; and
a digital chip including digital control circuitry and a counter whose count is frozen at counts which are proportional to the voltage of the respective signal samples in response to an output from the comparator. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An implantable cardiac stimulus device comprising first and second electrodes for sensing cardiac activity and circuitry for processing signals received from the electrodes, the circuitry including an analog chip and a digital chip, the circuitry further including a distributed analog-to-digital converter having at least a comparator providing an output signal indicating whether a most recent sample has an amplitude that is greater than or less than a next-most-recent sample, the comparator disposed on the analog chip, and a counter for receiving the comparator output, the counter disposed on the digital chip.
Specification