Current feedback techniques for capacitive sensing
First Claim
1. A processing system for a capacitive touch sensing device, comprising:
- an operational amplifier having a non-inverting input, an inverting input coupled to a sensor electrode, and an output;
a voltage source coupled to the non-inverting input and configured to input a control voltage to the operational amplifier;
a first voltage-controlled current source coupled to the sensor electrode and coupled between the output and the inverting input to form a feedback path to the operational amplifier to modify the control voltage to a modified control voltage and to modify an amount of charge stored in the sensor electrode,wherein the operational amplifier is configured to;
modify the control voltage based on the modified amount of charge stored in the sensor electrode; and
output the modified control voltage;
a second voltage-controlled current source coupled between the output and a capacitor and configured to modify a charge on the capacitor based on the modified control voltage at the output; and
a determination module coupled to the capacitor and configured to determine a capacitance measurement of the sensor electrode based on the modified charge on the capacitor.
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Accused Products
Abstract
Examples of the present disclosure generally provide current feedback techniques for capacitive sensing with an input device. A processing system for an input device includes an operational amplifier having a non-inverting input, an inverting input, and an output. A voltage source is coupled to the non-inverting input. A first voltage-controlled current source is coupled between the output and the inverting input to form a feedback path. A second voltage-controlled current source is coupled to the output and configured for modifying a charge on a capacitor based on a control voltage at the output. A determination module is coupled to the capacitor and configured for determining a capacitance measurement at the inverting input based on the charge on the capacitor.
24 Citations
25 Claims
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1. A processing system for a capacitive touch sensing device, comprising:
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an operational amplifier having a non-inverting input, an inverting input coupled to a sensor electrode, and an output; a voltage source coupled to the non-inverting input and configured to input a control voltage to the operational amplifier; a first voltage-controlled current source coupled to the sensor electrode and coupled between the output and the inverting input to form a feedback path to the operational amplifier to modify the control voltage to a modified control voltage and to modify an amount of charge stored in the sensor electrode, wherein the operational amplifier is configured to; modify the control voltage based on the modified amount of charge stored in the sensor electrode; and output the modified control voltage; a second voltage-controlled current source coupled between the output and a capacitor and configured to modify a charge on the capacitor based on the modified control voltage at the output; and a determination module coupled to the capacitor and configured to determine a capacitance measurement of the sensor electrode based on the modified charge on the capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A capacitive touch sensing device, comprising:
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a plurality of sensor electrodes; and a processing system coupled to the plurality of sensor electrodes, the processing system comprising; an operational amplifier having a non-inverting input, an inverting input coupled to at least one of the plurality of sensor electrodes, and an output; a voltage source coupled to the non-inverting input and configured to input a control voltage to the operational amplifier; a first voltage-controlled current source coupled to the at least one sensor electrode and coupled between the output and the inverting input to form a feedback path to the operational amplifier to modify the control voltage to a modified control voltage and to modify an amount of charge stored in the least one sensor electrode, wherein the operational amplifier is configured to; modify the control voltage based on the modified amount of charge stored in the at least one sensor electrode; and output the modified control voltage; a second voltage-controlled current source coupled between the output and a capacitor and configured to modify a charge on the capacitor based on the modified control voltage at the output; and a determination module coupled to the capacitor and configured to; determine a capacitance measurement associated with the at least one sensor electrode based on the modified charge on the capacitor; and determine positional information based on the capacitance measurement. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A method of capacitive touch sensing with a sensor electrode, the method comprising:
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driving an input voltage onto a non-inverting input of an operational amplifier, wherein a first voltage-controlled current source is coupled to the sensor electrode and coupled between an output of the operational amplifier and an inverting input of the operational amplifier to form a feedback path to the operational amplifier to modify the control voltage to a modified control voltage and to modify an amount of charge stored in the sensor electrode, wherein the operational amplifier is configured to; modify the control voltage based on the modified amount of charge stored in the sensor electrode; and output the modified control voltage; modifying, via a second voltage-controlled current source coupled between the output and a capacitor, a charge on the capacitor based on the modified control voltage at the output; and determining a capacitance measurement associated with the sensor electrode based on the modified charge on the capacitor. - View Dependent Claims (20, 21, 22, 23, 24, 25)
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Specification