Providing a baseline capacitance for a capacitance sensing channel
First Claim
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1. A capacitance-sensing circuit comprising:
- a channel input associated with measuring a capacitance of a unit cell of a capacitive sense array; and
a capacitive hardware baseliner coupled to the channel input, wherein the capacitive hardware baseliner comprises;
a programmable baseline capacitor;
a programmable baseline resistor; and
a current buffer with an input coupled to the programmable baseline capacitor and the programmable baseline resistor and an output coupled to the channel input,wherein the capacitive hardware baseliner generates a baseline current based on a time constant of the channel input associated with the measuring of the capacitance of the unit cell of the capacitive sense array using the programmable baseline capacitor and the programmable baseline resistor,wherein the capacitive hardware baseliner provides the baseline current at the channel input to provide a charge for a sense capacitor,wherein a change in the charge of the sense capacitor is provided by the baseline current indicating a presence of a touch object proximate to the unit cell.
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Abstract
A capacitance-sensing circuit may include a channel input associated with measuring a capacitance of a unit cell of a capacitive sense array. The capacitance-sensing circuit may also include a capacitive hardware baseliner that is coupled to the channel input. The capacitive hardware baseliner may generate a baseline current using a baseline capacitor and may provide the baseline current to the channel input.
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Citations
16 Claims
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1. A capacitance-sensing circuit comprising:
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a channel input associated with measuring a capacitance of a unit cell of a capacitive sense array; and a capacitive hardware baseliner coupled to the channel input, wherein the capacitive hardware baseliner comprises; a programmable baseline capacitor; a programmable baseline resistor; and a current buffer with an input coupled to the programmable baseline capacitor and the programmable baseline resistor and an output coupled to the channel input, wherein the capacitive hardware baseliner generates a baseline current based on a time constant of the channel input associated with the measuring of the capacitance of the unit cell of the capacitive sense array using the programmable baseline capacitor and the programmable baseline resistor, wherein the capacitive hardware baseliner provides the baseline current at the channel input to provide a charge for a sense capacitor, wherein a change in the charge of the sense capacitor is provided by the baseline current indicating a presence of a touch object proximate to the unit cell. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method comprising:
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generating, by a capacitive baseline circuit associated with a capacitive sense array, having an output current based on a set capacitance value of a programmable capacitor and a set resistance value of a programmable resistor, a time constant at a channel input of the capacitive sense array; buffering, by a current buffer coupled to the programmable capacitor and the programmable resistor, an input channel associated with the capacitive sense array, the output current to generate a buffered current; applying a gain factor to the buffered current to generate a baseline current; and providing the baseline current at the channel input associated with the capacitive sense array to provide a charge for a sense capacitor, wherein a change in the charge of the sense capacitor that is provided by the baseline current indicates a presence of a touch object at the capacitive sense array. - View Dependent Claims (12)
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13. A capacitive sense array system comprising:
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a plurality of unit cells, each unit cell comprising an electrode or a pair of electrodes; a plurality of channel inputs to measure capacitances of the plurality of unit cells; and a capacitive hardware baseliner coupled to the plurality of channel inputs, wherein the capacitive hardware baseliner comprises; a programmable baseline capacitor; a programmable baseline resistor; and a current buffer with an input coupled to the programmable baseline capacitor and the programmable baseline resistor and an output coupled to the one of the plurality of channel inputs, wherein the capacitive hardware baseliner generates a plurality of baseline currents based on a time constant of the channel inputs associated with the measuring of the capacitances of the unit cells of the capacitive sense array using the programmable baseline capacitor and the programmable baseline resistor, wherein the capacitive hardware baseliner provides the plurality of baseline currents at the plurality of channel inputs to provide a charge for a plurality of sense capacitors, wherein a change in one of the plurality of sense capacitors that is provided by the baseline current indicates a presence of a touch object proximate to the corresponding unit cell. - View Dependent Claims (14, 15, 16)
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Specification