MULTI-TOUCH RESOLVE MUTUAL CAPACITANCE SENSOR
First Claim
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1. A method of interfacing with a capacitive touch screen, comprising:
- charging an internal capacitor in the touch screen, which internal capacitor is disposed proximate a fixed location on the touch screen and is capable of changing in value in response to a touch at the fixed location; and
determining the value of the charge on the internal capacitor.
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Abstract
A method for interfacing with a capacitive touch screen is disclosed. The method includes charging an internal capacitor in the touch screen, which internal capacitor is disposed proximate a fixed location on the touch screen and is capable of changing in response to a touch at the specific location. After charging, the charge on the internal capacitor is transferred from the touch screen and the value of the charge on the internal capacitor then determined.
68 Citations
34 Claims
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1. A method of interfacing with a capacitive touch screen, comprising:
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charging an internal capacitor in the touch screen, which internal capacitor is disposed proximate a fixed location on the touch screen and is capable of changing in value in response to a touch at the fixed location; and determining the value of the charge on the internal capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of determining the value of an initial capacitance between a row line and a column line in a capacitive touch screen comprising a plurality of intersecting row and column lines, comprising the steps of:
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driving one of the row or column lines to a first voltage with an intersecting one of a column or row lines being connected to an external node external to the launch screen to charge the mutual capacitance at the intersection, the external node having a reference capacitor disposed thereon charged to a reference voltage; driving the one of the row or column lines to a second voltage with the reference node controlled to allow charge to be transferred between the mutual capacitance and the reference capacitor; and determining the value of the change of the charge on the reference capacitor. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23)
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24. A method for determining the value of charge on a Capacitor Under Test (CUT), comprising:
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charging a reference capacitor on a first node to a first charge level; transferring a substantially fixed percentage of the charge between the CUT and the reference capacitor such that the charge on the reference capacitor changes by the substantially fixed percentage of the charge transferred; isolating the CUT from the reference capacitor; determining the change in charge on the reference capacitor; and correlating the change in charge on the reference capacitor to the value of the charge on the CUT. - View Dependent Claims (25, 26, 27, 28, 29)
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30. A capacitance value sensor for determining a capacitance value corresponding to the value of an internal mutual capacitance in a touch screen display having intersecting first lines and second lines with the mutual capacitance disposed at the intersection of one of the first and second lines, comprising:
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a driver for driving the one of the first lines to drive one plate of the mutual capacitance from a first voltage to a second voltage level; and a capacitance sense circuit, including; a reference capacitor having one plate thereof connected to ground and the other plate thereof connected to a voltage node, a charging circuit operating in a first mode to connect the voltage node to the one of the second line with the driver operating to drive the one plate of the mutual capacitance to the first voltage level, the charging circuit charge the reference capacitor to a reference voltage level, transfer circuitry operating in a second mode and cause the driver to change the first voltage from the first to the second voltage level to transfer charge from the mutual capacitance to the reference capacitor, and a charge detect circuit operating in a third mode for determining the change in charge on the reference capacitor after transfer of charge thereto from the mutual capacitance and outputting a value for such change in charge, which value corresponds to the value of the mutual capacitance. - View Dependent Claims (31, 32, 33, 34)
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Specification