Single-electrode capacitance touchpad sensor systems
First Claim
1. A sensor for indicating the presence or absence of direct contact by a human member, comprising:
- a sensor common bus;
first means for receiving a driving signal of at least one sequential pulse of a substantially predetermined peak amplitude with respect to said common bus;
a touchpad electrode formed of a conductive or semiconductive material and adapted to be directly contacted by said member;
a linear first impedance element connected between said first means and said touchpad electrode;
a second impedance element connected between said common bus and the junction between said first impedance element and said touchpad electrode;
a sense amplifier having an output and first and second inputs, said first input connected to the common junction of said first and second impedance elements and said touchpad electrode; and
second means coupled to said sense amplifier second input for providing a reference potential independent of said driving signal and of an essentially constant and predetermined non-zero value less than the peak amplitude of the driving signal;
the output of said sense amplifier being in one of first and second conditions responsive respectively to the first input receiving portions of the driving signal respectively having greater than and less than the value provided by said second means in the respective presence and absence of contact of said touchpad electrode by said member.
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Accused Products
Abstract
Each of an array of capacitive touchpad sensors has a single touchpad electrode fabricated upon a substrate and accessible to user personnel, with series coupling and shunt capacitance being provided respectively between a driving generator and the touchpad electrode, and the touchpad electrode and an array ground. Each capacitive touchpad sensor operates with a sense amplifier to provide a high density sensor array requiring relatively low driving voltage amplitudes and may be utilized with driven shields and a normalization network to provide reliable capacitance sensing with reduced sensitivity to contamination of the surface of the sensor array.
146 Citations
20 Claims
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1. A sensor for indicating the presence or absence of direct contact by a human member, comprising:
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a sensor common bus; first means for receiving a driving signal of at least one sequential pulse of a substantially predetermined peak amplitude with respect to said common bus; a touchpad electrode formed of a conductive or semiconductive material and adapted to be directly contacted by said member; a linear first impedance element connected between said first means and said touchpad electrode; a second impedance element connected between said common bus and the junction between said first impedance element and said touchpad electrode; a sense amplifier having an output and first and second inputs, said first input connected to the common junction of said first and second impedance elements and said touchpad electrode; and second means coupled to said sense amplifier second input for providing a reference potential independent of said driving signal and of an essentially constant and predetermined non-zero value less than the peak amplitude of the driving signal; the output of said sense amplifier being in one of first and second conditions responsive respectively to the first input receiving portions of the driving signal respectively having greater than and less than the value provided by said second means in the respective presence and absence of contact of said touchpad electrode by said member. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In combination, a plurality of sensors for indicating the presence or absence of contact by a member, each sensor having:
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a sensor common bus; first means for receiving a driving signal of at least one sequential pulse of a substantially predetermined peak amplitude with respect to said common bus; a conductive touchpad electrode adapted to be contacted by said member; a first impedance element connected between said first means and said touchpad electrode; a second impedance element connected between said common bus and the junction between said first impedance element and said touchpad electrode; a sense amplifier having an output and first and second inputs, said first input connected to the common junction of first and second impedance elements and said touchpad electrode; and second means coupled to said sense amplifier second input for providing a reference potential of an essentially constant and predetermined value less than the peak amplitude of the driving signal; the output of said sense amplifier being in one of first and second conditions responsive respectively to the first input receiving portions of the driving signal respectively having greater than and less than the value provided by said second means in the respective presence and absence of contact of said touchpad electrode by said member; a planar substrate having a surface, said plurality of touchpad electrodes of said plurality of sensors being fabricated as conductive or semiconductive areas upon said substrate surface; the common buses of all of said plurality of sensors being coupled together; the first means of all of said plurality of sensors being coupled together to form a single receiving means; said reference potential providing means being coupled in parallel to all of the second inputs of the plurality of sense amplifiers; and a conductive shield electrode fabricated upon at least a portion of the substrate surface adjacent to, but insulated from, at least one of said plurality of touchpad electrodes; means for providing a second reference potential; and third means coupled to said shield electrode for providing an output signal when the magnitude of a current in said shield electrode exceeds a reference magnitude determined by the magnitude of the second reference potential. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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16. An array of sensors for performing a selected one of a plurality of data input functions responsive to contact by a member, said array comprising;
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a substrate having a surface; a two-dimensional array of conductive or semiconductive touchpad electrodes fabricated upon the surface of said substrate, each electrode of the array being electrically isolated from all other electrodes of the array; a system ground bus; means for providing a reference voltage of essentially constant magnitude; a sense amplifier having a first input, a second input receiving said reference voltage, and an output caused to be at one of first and second conditions responsive to a voltage at said first input being respectively greater than and less than the reference voltage at said second input; an impedance element coupled between said sense amplifier input and said common bus; a plurality of networks each having first, second and third terminals, the impedance of each network between pairs of said terminal being substantially identical to the impedance between like pairs of said terminals in all like networks;
the first terminal of each network being coupled to an associated one of said plurality of touchpad electrodes;a plurality of isolation impedances, each isolation impedance being coupled from a second terminal of an associated level-clamping network to said sense amplifier first input; means for generating a sequence of pulses having a peak voltage amplitude greater than the amplitude of said reference voltage; means for connecting the pulse generating means sequentially to the third terminal of successive ones of said plurality of networks; and means for recognizing a change in the condition of the output of said sense amplifier to determine which of said touchpad electrodes has been contacted by said member. - View Dependent Claims (17, 18, 19, 20)
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Specification