Capacitive sensor system with improved capacitance measuring sensitivity
First Claim
1. A capacitance sensor device comprising:
- a semiconductor integrated circuit;
a sensor electrode array arranged in a two dimensional array of n rows and m columns;
a shield electrode array arranged in a one dimensional array of n rows;
a quantity of m charge pump circuits;
a quantity of n switched level drivers with output levels of Vcc and 0, and when addressed, switching synchronous to the charge pump circuits, and with outputs connected to each of the n shield electrodes; and
a quantity of m blocks of n switches that allows the connection of one of the n sensor electrodes along a column to a charge pump circuit.
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Accused Products
Abstract
A capacitance sensor system and method includes a capacitive sensor as an array of sensor electrodes near the surface of the integrated circuit and charge pump circuits for measuring the capacitance at each sensor electrode. Shield electrodes and unused sense electrodes are used for background capacitance cancellation at each array location. The shield electrodes are switched between the circuit supply potentials in a manner synchronous to the capacitance sensing at the sense electrodes. The improved background capacitance cancellation allows all circuitry to be located outside the sensor array. The capacitance data is used to determine the positions of fingerprint artifacts and other fingerprint features.
122 Citations
42 Claims
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1. A capacitance sensor device comprising:
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a semiconductor integrated circuit; a sensor electrode array arranged in a two dimensional array of n rows and m columns; a shield electrode array arranged in a one dimensional array of n rows; a quantity of m charge pump circuits; a quantity of n switched level drivers with output levels of Vcc and 0, and when addressed, switching synchronous to the charge pump circuits, and with outputs connected to each of the n shield electrodes; and a quantity of m blocks of n switches that allows the connection of one of the n sensor electrodes along a column to a charge pump circuit. - View Dependent Claims (2, 3, 4, 5)
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6. A capacitance sensor system comprising:
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a semiconductor integrated circuit in which no transistor devices are beneath or between any sensor or shield electrodes; a plurality of sensor and shield electrodes; at least one reference electrode; a plurality of circuits;
whereinat least one of the plurality of shield electrodes separates at least one of the plurality of sensor electrodes from at least one reference electrode; and at least one of the plurality of sensor electrodes is disposed in a layered structure in a first plane that is entirely offset from a second plane in which at least one of the at least one reference electrode is disposed and is entirely offset from a third plane in which at least one of the plurality shield electrodes is disposed.
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7. A capacitance sensor device comprising:
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a semiconductor integrated circuit; a plurality of sensor electrodes arranged as an array; a plurality of shield electrodes; a plurality of amplifier circuits; a plurality of charge pump circuits; and a plurality of switches that allows the connection amongst the circuits and the electrodes;
whereinat least one of the plurality of sensor electrodes is disposed in a layered structure in a first plane that is entirely offset from a second plane in which at least one of the at least one reference electrode is disposed and is entirely offset from a third plane in which at least one of the plurality shield electrodes is disposed. - View Dependent Claims (8)
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9. A capacitive sensor for detecting capacitive variations associated with physical contact between a finger and a surface of the sensor, the capacitive sensor characterized in that:
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all electronic circuits other than electrodes are located physically outside an area associated with physical contact by the finger at which are disposed a plurality of sensor electrodes; and at least one shield electrode separates at least one of the plurality of sensor electrodes from at least one reference electrode;
whereinat least one sense electrode is disposed in a layered structure in a first plane that is entirely offset from a second plane in which at least one of the at least one reference electrode is disposed and is entirely offset from a third plane in which the at least one shield electrode is disposed. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method of operating a capacitive sensor to capture at least a portion of a fingerprint, the method comprising:
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measuring capacitance at a plurality of sense electrodes, no transistor devices being located between or beneath any of the sense electrodes, at least one shield electrode separating at least one of the plurality of sensor electrodes from at least one reference electrode; and reconstructing at least a portion of a fingerprint, based at least in part on the measured capacitance;
whereinthe measured capacitance is measured with at least one sense electrode disposed in a layered structure in a first plane that is entirely offset from a third plane in which at least one of the at least one shield electrode is disposed and is entirely offset from a second plane in which at least one reference electrode is disposed. - View Dependent Claims (24, 25, 26, 27, 28)
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29. A capacitance sensor system comprising:
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a semiconductor integrated circuit in which no transistor devices are beneath or between any sensor or shield electrodes; a plurality of sensor and shield electrodes; a plurality of circuits; a plurality of switches that allows the connection amongst the plurality of circuits and the plurality of sensor and shield electrodes; and at least one reference electrode, wherein each of said plurality of shield electrodes is placed beneath at least one of the plurality of sensor electrodes to separate the at least one of the plurality of sensor electrodes from at least one reference electrode.
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30. A capacitance sensor device comprising:
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a semiconductor integrated circuit; a plurality of sensor electrodes arranged as an array; a plurality of shield electrodes; a plurality of amplifier circuits; a plurality of charge pump circuits; a plurality of switches that allows the connection amongst the circuits and the electrodes; and at least one reference electrode, wherein each of said plurality of shield electrodes is placed beneath at least one of the plurality of sensor electrodes to separate the at least one of the plurality of sensor electrodes from at least one reference electrode.
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31. A capacitance sensor for detecting capacitive variations associated with physical contact between a finger and a surface of the sensor, the capacitive sensor characterized in that:
all electronic circuits other than a sense and a shield electrode are located physically outside an area associated with physical contact by the finger at which are disposed a plurality of sensor electrodes, further comprising at least one reference electrode wherein the shield electrode is placed beneath the sensor electrode to separate the sensor electrode from at least one reference electrode.
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32. A capacitive sensor comprising:
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a switched capacitor circuit; a sensor electrode connected to the switched capacitor circuit such that the switched capacitor circuit is configured to charge and discharge the sensor electrode; and a shield electrode connected to the switched capacitor circuit and placed beneath the sensor electrode to separate the sensor electrode from a reference electrode. - View Dependent Claims (33)
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34. A method of operating a capacitive sensor to capture at least a portion of a fingerprint, the method comprising:
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placing all transistor components outside a capacitive sensor sense elements area to reduce generation of optically induced electrical currents in the area; measuring capacitance at a plurality of sense electrodes based at least in part on the measured capacitance and reference capacitance cancellation using at least one reference electrode, the sense electrodes being separated from the at least one reference electrode by at least one shield electrode, the reference capacitance cancellation selected from the set consisting of localized reference capacitance cancellation, column-shared reference capacitance cancellation, and array-shared reference capacitance cancellation; and reconstructing at least a portion of a fingerprint, based at least in part on the measured capacitance;
whereinsaid transistor components are formed on a common substrate with said plurality of sense electrodes.
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35. A method of operating a capacitive sensor having a plurality of sensor electrodes to detect capacitive variations associated with an interaction between a finger and the capacitive sensor, comprising:
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locating all electronic circuits other than the plurality of sensor electrodes physically outside an area associated with interaction between the sensor and the finger and on a substrate on which the plurality of sensor electrodes are formed; sensing variations in capacitance among the plurality of sensor electrodes; and canceling capacitances in the sensed variations in capacitance among the plurality of sensor electrodes using reference capacitance cancellation using at least one reference electrode, the sense electrodes being separated from the at least one reference electrode by at least one shield electrode, the reference capacitance cancellation selected from the set consisting of;
localized reference capacitance cancellation, column-shared reference capacitance cancellation, an array-shared reference capacitance cancellation, and a row-shared reference cancellation.
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36. A capacitance sensor device in an integrated circuit comprising:
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a sensor electrode array arranged in a two dimensional array of n rows and m columns; a shield electrode array arranged in a one dimensional array of m columns and each configured to provide shielding between a column of sensor electrode and at least one reference electrode; a quantity of m charge pump circuits; a quantity of m amplifiers each having an input connected to a respective one of the charge pump circuits and an output connected to a respective shield electrode in the shield electrode array; first m groups of n switches, each of the first m groups of n switches associated with a respective column in the sensor electrode array and coupled between respective ones of the sensor electrodes in the column and the output of a respective one of the m amplifiers; and second m groups of n switches, each of the second m groups of n switches associated with a respective column in the sensor electrode array and coupled between respective ones of the sensor electrodes in the column and the output of a respective one of the m charge pumps. - View Dependent Claims (37)
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38. A capacitance sensor device in an integrated circuit comprising:
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a sensor electrode array arranged in a two dimensional array of n rows and m columns; a shield electrode array arranged in a one dimensional array of m columns; a quantity of m charge pump circuits each having an output connected to a respective shield electrode in the shield electrode array; a quantity of m switch cancellation circuit each configured to switch between first and second output levels synchronously with an output of the respective one of the charge pump circuits; first m groups of n switches, each of the first m groups of n switches associated with a respective column in the sensor electrode array and coupled between respective ones of the sensor electrodes in the column and the output of a respective one of the m switched level drivers; and second m groups of n switches, each of the second m groups of n switches associated with a respective column in the sensor electrode array and coupled between respective ones of the sensor electrodes in the column and the output of a respective one of the m charge pumps. - View Dependent Claims (39)
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40. A capacitance sensor device in an integrated circuit comprising:
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a sensor electrode array arranged in a two dimensional array of n rows and m columns; a shield electrode array arranged in a one dimensional array of n rows; a quantity of m charge pump circuits; a quantity of n switched level drivers each having an output connected to a respective one of the n shield electrodes, and when addressed, switching synchronously to a selected one of the charge pump circuits and between output levels of Vcc and 0; and a quantity of m blocks of n switches, each block of n switches corresponding to a column in the sensor electrode array and coupled between respective ones of the sensor electrodes in the column and one of the m charge pump circuits. - View Dependent Claims (41)
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42. A capacitance sensor system comprising:
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a plurality of sensor electrodes; a plurality of shield electrodes each configured to provide shielding between at least one sensor electrode and at least one reference electrode; a plurality of charge pump circuits each associated with a group of sensor electrodes; and a plurality of switch cancellation circuits each associated with at least one shield electrode and configured to switch synchronously with a switch in a respective one of the charge pump circuits;
whereinat least one of the plurality of shield electrodes is disposed in a plane that is offset along a vertical axis from a different plane in which at least one of the plurality of sensor electrodes is disposed.
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Specification