High resolution capacitance to code converter
First Claim
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1. An apparatus comprising:
- an integration circuit comprising a first capacitor and a second capacitor, the integration circuit coupled to a capacitive sense array;
a comparator, operatively coupled to the integration circuit, to compare a first capacitor voltage of the first capacitor to a reference voltage and produce a first comparator output based on the comparison;
a current generator, operatively coupled with the integration circuit, the current generator configured to balance charge on the first capacitor, the second capacitor configured to integrate charge when the current generator balances charge on the first capacitor, and be charge balanced by the current generator when the first capacitor integrates charge; and
a control unit, operatively coupled to the comparator and the current generator, the control unit configured to balance charge on the first capacitor by sensing the first comparator output and controlling the current generator based on the first comparator output.
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Abstract
An integration circuit including a first capacitor is operatively coupled to a comparator. The comparator is configured to compare a first capacitor voltage of the first capacitor to a reference voltage and produce a first comparator output based on the comparison. A current generator is operatively coupled with the integration circuit and configured to balance charge on the first capacitor. A control unit is operatively coupled to the comparator and the current generator and configured to balance charge on the first capacitor by sensing the first comparator output and controlling the current generator based on the first comparator output.
20 Citations
18 Claims
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1. An apparatus comprising:
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an integration circuit comprising a first capacitor and a second capacitor, the integration circuit coupled to a capacitive sense array; a comparator, operatively coupled to the integration circuit, to compare a first capacitor voltage of the first capacitor to a reference voltage and produce a first comparator output based on the comparison; a current generator, operatively coupled with the integration circuit, the current generator configured to balance charge on the first capacitor, the second capacitor configured to integrate charge when the current generator balances charge on the first capacitor, and be charge balanced by the current generator when the first capacitor integrates charge; and a control unit, operatively coupled to the comparator and the current generator, the control unit configured to balance charge on the first capacitor by sensing the first comparator output and controlling the current generator based on the first comparator output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method comprising:
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integrating charge on a first capacitor, the first capacitor coupled to a capacitive sense array; comparing a first capacitor voltage on the first capacitor to a reference voltage at a comparator, the comparator to produce a first comparator output based on a first comparison; balancing, by a current generator, charge on the first capacitor based on the first comparator output of the first comparison; measuring a charge balancing period, based on the charge balancing, by the current generator, on the first capacitor; and accumulating a quantization error over successive charge balancing periods. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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16. A system comprising:
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a capacitance-sensing circuit configured to measure touch data from a capacitive sense array, the capacitance-sensing circuit comprising; a first capacitor configured to alternately integrate charge or balance charge; a second capacitor configured to alternately integrate charge or balance charge; a comparator, operatively coupled to the first capacitor to compare a first capacitor voltage of the first capacitor to a reference voltage and produce a first comparator output based on the comparison; a current generator, operatively coupled with the first capacitor, the current generator configured to balance charge on the first capacitor, the second capacitor configured to integrate charge when the current generator balances charge on the first capacitor, and the current generator configured to balance charge on the second capacitor when the first capacitor integrates charge; and a control unit, operatively coupled to the comparator and the current generator, the control unit configured to balance charge on the first capacitor by sensing the first comparator output and controlling the current generator based on the first comparator output. - View Dependent Claims (17, 18)
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Specification