Charge accumulation capacitance sensor with linear transfer characteristic
First Claim
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1. An apparatus, comprising:
- a first capacitor; and
a capacitance sensing circuit comprising a second capacitor selectively connectable to the first capacitor, wherein the capacitance sensing circuit is configured to transfer charge linearly from the first capacitor to the second capacitor for a plurality of cycles and to determine a value of the first capacitor;
a buffer amplifier comprising an input terminal and an output terminal, wherein the input terminal is coupled to the second capacitor; and
an adder to add an offset voltage to an output of the buffer amplifier, the adder comprising a first terminal and a second terminal, wherein the first terminal is coupled to the output terminal of the buffer amplifier and wherein the second terminal is selectively connectable to the first capacitor.
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Abstract
A method and apparatus for capacitance sensing uses an offset feedback voltage to linearize a charge-transfer characteristic.
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Citations
11 Claims
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1. An apparatus, comprising:
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a first capacitor; and a capacitance sensing circuit comprising a second capacitor selectively connectable to the first capacitor, wherein the capacitance sensing circuit is configured to transfer charge linearly from the first capacitor to the second capacitor for a plurality of cycles and to determine a value of the first capacitor; a buffer amplifier comprising an input terminal and an output terminal, wherein the input terminal is coupled to the second capacitor; and an adder to add an offset voltage to an output of the buffer amplifier, the adder comprising a first terminal and a second terminal, wherein the first terminal is coupled to the output terminal of the buffer amplifier and wherein the second terminal is selectively connectable to the first capacitor. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An apparatus, comprising:
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a first capacitor; and a capacitance sensing circuit comprising a second capacitor selectively connectable to the first capacitor, wherein the capacitance sensing circuit is configured to transfer charge linearly to the first capacitor from the second capacitor for a plurality of cycles; a reference voltage selectively connectable to the second capacitor; a buffer amplifier comprising an input terminal and an output terminal, wherein the input terminal is coupled to the second capacitor; and a voltage source comprising a first terminal and a second terminal, wherein the first terminal is coupled to the output terminal of the buffer amplifier and wherein the second terminal is selectively connectable to the first capacitor. - View Dependent Claims (8, 9, 10, 11)
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Specification