Capacitive interface circuit for low power sensor system
First Claim
1. An implantable medical device, comprising:
- a correlated sampling circuit that reduces one or more noise components in an output signal, the correlated sampling circuit comprising;
a differential amplifier that amplifies a sensor signal to produce the output signal, wherein the differential amplifier comprises a first input, a second input, and an output; and
a sampling capacitor comprising an input coupled to the output of the differential amplifier, wherein the sampling capacitor stores the output signal; and
a clock distribution network that controls the correlated sampling circuit,wherein the correlated sampling circuit controls the first and second inputs of the differential amplifier, responsive to timing signals provided by the clock distribution network, such that the differential amplifier amplifies the one or more noise components during at least a portion of a first clock phase and amplifies the sensor signal with the one or more noise components during a second clock phase, to reduce the one or more noise components in the output signal.
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Abstract
A capacitive interface circuit for a low power system is described. The capacitive interface circuit is configured to achieve very low noise sensing of capacitance-based transducers, such as a micro-electro-mechanical system (MEMS)-based sensor, with high resolution and low power. The capacitive interface circuit uses a differential amplifier and correlated triple sampling (CTS) to substantially eliminate, or at least reduce, kT/C noise, as well as amplifier offset and flicker (1/f) noise, from the output of the amplifier. The capacitive interface circuit may further include an output stage that reduces glitching, i.e., clock transients, in the output signal by allowing transients in the amplifier output to settle. In this manner, the circuit can be used in a low power system to produce a stable, low-noise output.
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Citations
43 Claims
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1. An implantable medical device, comprising:
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a correlated sampling circuit that reduces one or more noise components in an output signal, the correlated sampling circuit comprising; a differential amplifier that amplifies a sensor signal to produce the output signal, wherein the differential amplifier comprises a first input, a second input, and an output; and a sampling capacitor comprising an input coupled to the output of the differential amplifier, wherein the sampling capacitor stores the output signal; and a clock distribution network that controls the correlated sampling circuit, wherein the correlated sampling circuit controls the first and second inputs of the differential amplifier, responsive to timing signals provided by the clock distribution network, such that the differential amplifier amplifies the one or more noise components during at least a portion of a first clock phase and amplifies the sensor signal with the one or more noise components during a second clock phase, to reduce the one or more noise components in the output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method for operating an implantable medical device, comprising:
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amplifying, via a differential amplifier, a differential sensor signal to produce an output signal, wherein the differential amplifier comprises a first input, a second input, and an output; storing the output signal on a sampling capacitor comprising an input coupled to the output of the differential amplifier; and applying a correlated sampling process to reduce one or more noise components in the output signal, wherein applying the correlated sampling process includes controlling the first and second inputs of the differential amplifier, responsive to timing signals provided by a clock distribution network, such that the differential amplifier amplifies the one or more noise components during at least a portion of a first clock phase and amplifies the differential sensor signal with the one or more noise components during a second clock phase, to reduce the one or more noise components in the output signal. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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43. An implantable medical device, comprising:
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means for amplifying a differential sensor signal to produce an output signal, wherein the means for amplifying comprises a first input, a second input, and an output; means for storing the output signal on a sampling capacitor coupled to the output of the means for amplifying; and means for applying a correlated sampling process that reduces one or more noise components in the output signal, wherein the means for applying the correlated sampling process comprises means for controlling the first and second inputs of the means for amplifying, responsive to timing signals provided by a clock distribution network that controls the means for applying, such that the means for amplifying amplifies the one or more noise components during at least a portion of a first clock phase and amplifies the differential sensor signal with the one or more noise components during a second clock phase, to reduce the one or more noise components in the output signal.
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Specification