Capacitive sensing array modulation
First Claim
1. An electronic device, comprising:
- a capacitive sensor comprising;
a sensor pad comprising an array of individual capacitive sensing elements, the sensor pad configured to receive;
a sensor pad ground reference voltage greater than earth ground; and
a sensor pad supply voltage;
a ring surrounding the sensor pad and maintained at a system ground reference voltage, the ring elevated with respect to the sensor pad and configured for direct contact by user'"'"'s fingertip; and
a dielectric entirely covering the sensor pad and positioned within the ring;
a modulating circuit operably connected to the sensor pad and adapted to modulate the sensor pad supply voltage relative to the sensor pad ground reference voltage;
a inductive boost circuit configured to provide the sensor pad ground reference voltage to the sensor pad; and
a housing surrounding the modulating circuit and the inductive boost circuit;
wherein;
the sensor pad ground reference voltage is greater than the system ground.
1 Assignment
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Accused Products
Abstract
A capacitive fingerprint sensor that may be formed of an array of sensing elements. Each capacitive sensing element of the array may register a voltage that varies with the capacitance of a capacitive coupling. A finger may capacitively couple to the individual capacitive sensing elements of the sensor, such that the sensor may sense a capacitance between each capacitive sensing element and the flesh of the fingerprint. The capacitance signal may be detected by sensing the change in voltage on the capacitive sensing element as the relative voltage between the finger and the sensing chip is changed. Alternately, the capacitance signal may be detected by sensing the change in charge received by the capacitive sensing elements as the relative voltage between the finger and the sensing chip is changed.
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Citations
17 Claims
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1. An electronic device, comprising:
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a capacitive sensor comprising; a sensor pad comprising an array of individual capacitive sensing elements, the sensor pad configured to receive; a sensor pad ground reference voltage greater than earth ground; and a sensor pad supply voltage; a ring surrounding the sensor pad and maintained at a system ground reference voltage, the ring elevated with respect to the sensor pad and configured for direct contact by user'"'"'s fingertip; and a dielectric entirely covering the sensor pad and positioned within the ring; a modulating circuit operably connected to the sensor pad and adapted to modulate the sensor pad supply voltage relative to the sensor pad ground reference voltage; a inductive boost circuit configured to provide the sensor pad ground reference voltage to the sensor pad; and a housing surrounding the modulating circuit and the inductive boost circuit;
wherein;the sensor pad ground reference voltage is greater than the system ground. - View Dependent Claims (2, 3, 4, 5, 6, 7, 9, 10)
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8. An electronic device, comprising:
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a sensor pad comprising an array of individual capacitive sensing elements and configured to receive a sensor pad ground reference voltage and a sensor pad supply voltage; a dielectric positioned over the sensor pad configured for direct contact by a user'"'"'s fingertip; a ring surrounding the sensor pad and configured for direct contact by the user'"'"'s fingertip, the ring maintained at a system ground reference voltage; and a modulating circuit adapted to control the sensor pad supply voltage and to maintain the sensor pad supply voltage relative to the sensor pad ground reference voltage;
whereinthe sensor pad ground reference voltage exceeds the system ground reference voltage; and the system ground reference voltage is greater than earth ground.
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11. A method for operating a capacitive sensor, wherein the capacitive sensor includes a sensor pad comprising an array of individual capacitive sensing elements, a dielectric positioned over the sensor pad, and a ring that is adjacent to, surrounds and is in an elevated position with respect to the sensor pad, the method comprising:
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during a scanning state and when the ring is directly contacted by user'"'"'s fingertip, modulating a sensor pad supply voltage and a sensor pad ground reference voltage received by the sensor pad while maintaining the ring at a system ground level greater than earth ground; and during an idle state, maintaining the supply voltage received by the sensor pad at a boosted ground that exceeds the system ground level;
whereinthe sensor pad ground reference voltage is boosted with respect to the system ground level. - View Dependent Claims (12)
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13. A method for operating a capacitive sensor, wherein the capacitive sensor includes a sensor pad comprising an array of individual capacitive sensing elements, a dielectric covering the sensor pad, and a ring that surrounds and is elevated with respect to the sensor pad, the method comprising:
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initiating a scanning operation when user'"'"'s fingertip is in direct contact with the ring when the ring is coupled to a system ground level greater than earth ground; reading a first signal from a capacitive sensing element of the array of individual capacitive sensing elements when a sensor pad supply voltage supplied to the sensor pad is in a low state relative to a sensor pad ground reference voltage; and reading a second signal from the capacitive sensing element when the sensor pad ground reference voltage is supplied to the sensor pad and is greater than the system ground level. - View Dependent Claims (14, 15, 16, 17)
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Specification