Device and method for reading a capacitive sensor, in particular of a micro-electromechanical type
First Claim
1. A read device of a capacitive sensor, comprising:
- modulated signal source structured to generate a modulated electrical read signal and supply said modulated electrical read signal to said capacitive sensor;
a discrete-time sense circuit, connectable to said capacitive sensor, for generating a first electrical output signal, correlated to capacitance variations of said capacitive sensor, in response to variations of said electrical read signal;
a demodulator stage, connected to said sense circuit, for demodulating said first electrical output signal and generating a demodulated second electrical output signal; and
a low-pass filtering stage, connected to said demodulator stage, for generating a filtered third electrical output signal, on the basis of said second electrical output signal; and
a phase generator structured to control the modulated signal source in first and second read cycles in which the second read cycle is consecutive to said first read cycle, each read cycle including a reset phase and a sense phase, the modulated electrical read signal presenting a first value in the reset phase of the first read cycle, a second value in the sense phase of the first read cycle, the second value in the reset phase of the second read cycle, and the first value in the sense phase of the second read cycle.
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Abstract
A read device of a capacitive sensor includes: a signal source supplying an electrical read signal for driving the capacitive sensor; and a discrete-time sense circuit for generating an electrical output signal, correlated to variations of capacitance of the capacitive sensor, in response to variations of the electrical read signal. The device moreover includes: a modulator stage for generating a modulated electrical read signal on the basis of the electrical read signal and supplying the modulated electrical read signal to the capacitive sensor; a demodulator stage, connected to the sense circuit, for demodulating the electrical output signal and generating a demodulated electrical output signal; and a low-pass filtering stage for generating a filtered electrical output signal, on the basis of the modulated electrical output signal.
83 Citations
31 Claims
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1. A read device of a capacitive sensor, comprising:
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modulated signal source structured to generate a modulated electrical read signal and supply said modulated electrical read signal to said capacitive sensor; a discrete-time sense circuit, connectable to said capacitive sensor, for generating a first electrical output signal, correlated to capacitance variations of said capacitive sensor, in response to variations of said electrical read signal; a demodulator stage, connected to said sense circuit, for demodulating said first electrical output signal and generating a demodulated second electrical output signal; and a low-pass filtering stage, connected to said demodulator stage, for generating a filtered third electrical output signal, on the basis of said second electrical output signal; and a phase generator structured to control the modulated signal source in first and second read cycles in which the second read cycle is consecutive to said first read cycle, each read cycle including a reset phase and a sense phase, the modulated electrical read signal presenting a first value in the reset phase of the first read cycle, a second value in the sense phase of the first read cycle, the second value in the reset phase of the second read cycle, and the first value in the sense phase of the second read cycle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A detecting apparatus comprising:
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a capacitive sensor; and a read device that includes; a modulated signal source structured to generate a modulated electrical read signal and supply said modulated electrical read signal to said capacitive sensor; a discrete-time sense circuit connectable to said capacitive sensor and structured to generate a first electrical output signal, correlated to capacitance variations of said capacitive sensor, in response to variations of said first electrical read signal; a demodulator stage connected to said sense circuit and structured to demodulate said first electrical output signal and generate a demodulated second electrical output signal; a low-pass filtering stage connected to said demodulator stage and structured to generate a filtered third electrical output signal based on said second electrical output signal; and a phase generator structured to control the modulated signal source in first and second read cycles in which the second read cycle is consecutive to said first read cycle, each read cycle including a reset phase and a sense phase, the modulated electrical read signal presenting a first value in the reset phase of the first read cycle, a second value in the sense phase of the first read cycle, the second value in the reset phase of the second read cycle, and the first value in the sense phase of the second read cycle. - View Dependent Claims (15, 16, 17, 18)
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19. An electronic device, comprising:
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a processing unit; a capacitive sensor; and a read device coupled to the processing unit and including; a modulated signal source structured to generate a modulated electrical read signal and supply said modulated electrical read signal to said capacitive sensor; a discrete-time sense circuit connectable to said capacitive sensor and structured to generate a first electrical output signal, correlated to capacitance variations of said capacitive sensor, in response to variations of said first electrical read signal; a demodulator stage connected to said sense circuit and structured to demodulate said first electrical output signal and generate a demodulated second electrical output signal; and a phase generator structured to control the modulated signal source in first and second read cycles in which the second read cycle is consecutive to said first read cycle, each read cycle including a reset phase and a sense phase, the modulated electrical read signal presenting a first value in the reset phase of the first read cycle, a second value in the sense phase of the first read cycle, the second value in the reset phase of the second read cycle, and the first value in the sense phase of the second read cycle. - View Dependent Claims (20, 21, 22, 23, 24)
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25. A method for reading a capacitive sensor, comprising:
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generating a modulated electrical read signal; driving said capacitive sensor by said modulated electrical read signal; discrete-time generating a first electrical output signal correlated to variations of capacitance of said capacitive sensor, in response to variations of said first electrical read signal; demodulating said first electrical output signal for generating a demodulated second electrical output signal; and low-pass filtering said second electrical output signal for generating a filtered third electrical output signal, wherein generating the modulated electrical read signal includes; providing the modulated electrical read signal as a first value in a reset phase of a first read cycle; providing the modulated electrical read signal as a second value in a sense phase of the first read cycle; providing the modulated electrical read signal as the second value in a reset phase of a second read cycle that is consecutive to the first read cycle; and providing the modulated electrical read signal as the first value in a sense phase of the second read cycle. - View Dependent Claims (26, 27, 28, 29, 30, 31)
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Specification