Noise handling in capacitive touch sensors
First Claim
1. A method of measuring proximity of a body to a capacitive sensor device comprising a coupling capacitor having a capacitance sensitive to proximity of a body, and a charge accumulation capacitor having first and second plates, the first plate being connected to the coupling capacitor, and the second plate being connected to a voltage output line, the method comprising:
- making a signal measurement by transferring charge indicative of the capacitance of the coupling capacitor from the coupling capacitor to the charge accumulation capacitor, and by reading the voltage on the voltage output line, thereby to measure proximity of a body; and
making a noise measurement by emulating the signal measurement, but inhibiting charge from arising on the coupling capacitor as a result of proximity of a body, thereby to transfer charge indicative of noise induced on the coupling capacitor to the charge accumulation capacitor, and by reading the voltage on the voltage output line, thereby to measure noise.
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Accused Products
Abstract
In a capacitive sensor of the type having X electrodes which are driven and Y electrodes that are used as sense channels connected to charge measurement capacitors, signal measurements may be made by driving the X electrodes to transfer successive packets of charge to the charge measurement capacitors. An additional noise measurement may be made by emulating or mimicking the signal measurement, but in certain embodiments without driving the X electrodes. The packets of charge transferred to the charge accumulation capacitor may be indicative of noise induced on the XY sensing nodes. These noise measurements can be used to configure post-processing of the signal measurements.
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Citations
14 Claims
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1. A method of measuring proximity of a body to a capacitive sensor device comprising a coupling capacitor having a capacitance sensitive to proximity of a body, and a charge accumulation capacitor having first and second plates, the first plate being connected to the coupling capacitor, and the second plate being connected to a voltage output line, the method comprising:
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making a signal measurement by transferring charge indicative of the capacitance of the coupling capacitor from the coupling capacitor to the charge accumulation capacitor, and by reading the voltage on the voltage output line, thereby to measure proximity of a body; and making a noise measurement by emulating the signal measurement, but inhibiting charge from arising on the coupling capacitor as a result of proximity of a body, thereby to transfer charge indicative of noise induced on the coupling capacitor to the charge accumulation capacitor, and by reading the voltage on the voltage output line, thereby to measure noise. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A capacitive sensor device comprising a coupling capacitor having a capacitance sensitive to proximity of a body, and a charge accumulation capacitor having first and second plates, the first plate being connected to the coupling capacitor, and the second plate being connected to a voltage output line,
the device being operable in a first mode to make a signal measurement by transferring charge indicative of the capacitance of the coupling capacitor from the coupling capacitor to the charge accumulation capacitor, wherein the voltage on the voltage output line is a measure of proximity of a body; - and
the device being operable in a second mode to make a noise measurement by emulating the signal measurement, but inhibiting charge from arising on the coupling capacitor as a result of proximity of a body, thereby to transfer charge indicative of noise induced on the coupling capacitor to the charge accumulation capacitor, wherein the voltage on the voltage output line is a measure of noise. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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Specification