Capacitance to code converter with sigma-delta modulator
First Claim
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1. A method, comprising:
- measuring a capacitance on a sensor element of a sensing device using a sigma-delta modulator, wherein the sensor element is a switching capacitor in a feedback loop of the sigma-delta modulator;
switching the switching capacitor between a voltage source and a first node of a modulator capacitor of the sigma-delta modulator to provide a charge current to the modulator capacitor using a plurality of switches, wherein a first of the plurality of switches is coupled between the voltage source and a first node of the switching capacitor and the second of the plurality of switches is coupled between the first node of the switching capacitor and the first node of the modulator capacitor; and
converting the capacitance measured on the sensor element to a digital code.
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Abstract
An apparatus and method for converting a capacitance measured on a sensor element to a digital code. The apparatus may include a switching capacitor as a sensor element of a sensing device, and a sigma-delta modulator coupled to the sensor element to convert a capacitance measured on the sensor element to a digital code. The switching capacitor is in a feedback loop of the sigma-delta modulator. The method may include measuring a capacitance on a sensor element of a sensing device using a sigma-delta modulator, and converting the capacitance measured on the sensor element to a digital code.
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Citations
58 Claims
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1. A method, comprising:
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measuring a capacitance on a sensor element of a sensing device using a sigma-delta modulator, wherein the sensor element is a switching capacitor in a feedback loop of the sigma-delta modulator; switching the switching capacitor between a voltage source and a first node of a modulator capacitor of the sigma-delta modulator to provide a charge current to the modulator capacitor using a plurality of switches, wherein a first of the plurality of switches is coupled between the voltage source and a first node of the switching capacitor and the second of the plurality of switches is coupled between the first node of the switching capacitor and the first node of the modulator capacitor; and converting the capacitance measured on the sensor element to a digital code. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An apparatus, comprising:
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a sensor element, wherein the sensor element is a switching capacitor; a sigma-delta modulator coupled to the sensor element, wherein the switching capacitor is in a feedback loop of the sigma-delta modulator; and a switching circuit having a plurality of switches, wherein a first of the plurality of switches is coupled between a voltage source and a first node of the switching capacitor and the second of the plurality of switches is coupled between the first node of the switching capacitor and a first node of a modulator capacitor of the sigma-delta modulator, wherein the switching capacitor is configured to provide a charge current to the modulator capacitor using the second switch, wherein the sigma-delta modulator is configured to measure a capacitance on the sensor element using the plurality of switches, wherein the switching capacitor is configured to provide a charge current to the modulator capacitor using the second switch, and wherein the sigma-delta modulator is configured to convert the measured capacitance to a digital code. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40)
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41. An apparatus, comprising:
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a sensor element, wherein the sensor element is a switching capacitor; and a sigma-delta modulator coupled to the sensor element to measure a capacitance on the sensor element and to convert the measured capacitance to a digital code, wherein the switching capacitor is in a feedback loop of the sigma-delta modulator, wherein the sigma-delta modulator further comprises; a comparator configured to receive two inputs, wherein the two inputs are the voltage on the modulator capacitor and the reference voltage; a latch coupled to an output of the comparator, wherein the latch is configured to latch the output of the comparator based on a clock signal; and a control circuit coupled to receive an output of the latch and the clock signal, wherein the control circuit is configured to control the first and second switches of the switching circuit. - View Dependent Claims (42, 43, 44, 45, 46)
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47. An apparatus, comprising:
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a sensor element, wherein the sensor element is a switching capacitor; and a sigma-delta modulator coupled to the sensor element to measure a capacitance on the sensor element and to convert the measured capacitance to a digital code, wherein the switching capacitor is in a feedback loop of the sigma-delta modulator; a clock generation circuit coupled to the sigma-delta modulator, wherein the clock generation circuit is configured to provide a clock to the switching circuit; and a digital filter coupled to the sigma-delta modulator, wherein the digital filter is configured to filter the output of the sigma-delta modulator. - View Dependent Claims (48, 49, 50, 51, 52, 53, 54, 55, 56, 57)
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58. A method, comprising:
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measuring a capacitance on a sensor element of a sensing device using a sigma-delta modulator, wherein the sensor element is a switching capacitor in a feedback loop of the sigma-delta modulator; and converting the capacitance measured on the sensor element to a digital code, wherein measuring the capacitance further comprises; charging a modulator capacitor of the sigma-delta modulator using a first charge on the switching capacitor to increase a voltage on the modulator capacitor; when the voltage is equal to a reference voltage, discharging the modulator capacitor until the voltage is equal to the reference voltage; and charging the modulator capacitor using a second charge on the switching capacitor to increase the voltage on the modulator capacitor.
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Specification