METHOD AND APPARATUS FOR IMPROVING DYNAMIC RANGE OF A TOUCHSCREEN CONTROLLER
First Claim
1. A capacitance-to-voltage converter for use with a capacitive touchscreen having one or more capacitance sensors, the converter comprising:
- a. a capacitance offset cancellation element coupled for alleviating effects of parasitic capacitance on signals produced by one or more of the capacitance sensors; and
b. a analog-to-digital converter coupled to the offset cancellation element for converting the signals to digital signals.
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Accused Products
Abstract
A touchscreen system for increasing the dynamic range of the system comprising a touchscreen coupled to an offset cancellation element and a capacitance measuring element. The offset cancellation element is configured to be dynamically changed in capacitance such that it offsets parasitic and sensor capacitances of the touchscreen sensors thereby leaving only touch event capacitance to be measured by the measuring element. The offset cancellation element is able to adjust to the initial unwanted capacitances of each sensor as well as dynamically adjust to changes in the unwanted capacitance due to the environment. In some embodiments, the offset cancellation element is a capacitance digital-to-analog converter that is controlled by a controller for offsetting the unwanted capacitance. As a result, the touchscreen system is able to utilize a small integrating capacitor thereby lowering cost and improving the dynamic range of the system.
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Citations
46 Claims
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1. A capacitance-to-voltage converter for use with a capacitive touchscreen having one or more capacitance sensors, the converter comprising:
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a. a capacitance offset cancellation element coupled for alleviating effects of parasitic capacitance on signals produced by one or more of the capacitance sensors; and b. a analog-to-digital converter coupled to the offset cancellation element for converting the signals to digital signals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A touchscreen system comprising:
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a. a capacitive touch screen having one or more capacitance sensors; and b. a capacitance-to-voltage converter comprising; i. a capacitance offset cancellation element coupled for alleviating effects of parasitic capacitance on signals produced by one or more of the capacitance sensors; and ii. a analog-to-digital converter coupled to the offset cancellation element for converting the signals to digital signals. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method of improving dynamic range of a capacitance-to-voltage converter for use with a touchscreen having one or more capacitance sensors, the method comprising:
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a. determining an average digital output over a period with a controller, wherein the average digital output is associated with a sensor of the converter; and b. adjusting an offset value produced by an offset cancellation element of the converter until the digital output of the converter is equal to a predetermined baseline value. - View Dependent Claims (30, 31, 32, 33, 34, 35, 36, 37)
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38. A method of improving dynamic range in a capacitance-to-voltage converter for use with a touchscreen having one or more capacitance sensors, the method comprising:
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a. averaging a digital output associated with a sensor of the converter in order to determine a baseline value; b. determining a baseline threshold value; and c. dynamically adjusting an offset value of an offset cancellation element of the converter by a delta value if the baseline value reaches the baseline threshold value such that the baseline value is distanced from the threshold value. - View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46)
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Specification