Method and circuit for detecting movements through micro-electric-mechanical sensors, compensating parasitic capacitances and spurious movements
First Claim
1. A method for compensating parasitic capacitances in a micro-electric-mechanical sensor having a fixed body and a moving mass, forming first and second detection capacitors, connected to a common node and to a first and second detection node respectively and having a common rest detection capacitance, the method comprising:
- feeding said common node with a detection voltage; and
maintaining said first and second detection node at a constant common mode voltage through a feedback voltage, the maintaining step including feeding said common node with a compensating electric quantity, inversely proportional to said common rest detection capacitance in at least one predetermined interval.
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Abstract
Method for detecting movements through a micro-electric-mechanical sensor, having a fixed body and a moving mass, forming at least one first and one second detection capacitor, connected to a common node and to a first, respectively a second detection node and having a common detection capacitance at rest and a capacitive unbalance in case of a movement. The method includes the steps of: feeding the common node with a constant detection voltage of predetermined duration; generating a feedback voltage to maintain the first and the second detection node at a constant common mode voltage; generating a compensation electric quantity, inversely proportional to the common detection capacitance at least in one predetermined range; supplying the compensating electric quantity to the common node; and detecting an output quantity related to the capacitive unbalance.
29 Citations
26 Claims
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1. A method for compensating parasitic capacitances in a micro-electric-mechanical sensor having a fixed body and a moving mass, forming first and second detection capacitors, connected to a common node and to a first and second detection node respectively and having a common rest detection capacitance, the method comprising:
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feeding said common node with a detection voltage; and
maintaining said first and second detection node at a constant common mode voltage through a feedback voltage, the maintaining step including feeding said common node with a compensating electric quantity, inversely proportional to said common rest detection capacitance in at least one predetermined interval. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for detecting a movement of a micro-electric-mechanical sensor having a fixed body and a moving mass, forming first and second detection capacitors, connected to a common node and to first and second detection nodes, respectively, and having a common detection rest capacitance and a capacitive unbalance following a movement of said moving mass;
- the method comprising;
feeding said common node with a detection voltage;
maintaining said first and the second detection node at a constant common mode voltage through a feedback voltage;
detecting an output quantity related to said capacitive unbalance; and
_feeding said common node with a compensating electric quantity, inversely proportional to said common detection rest capacitance in at least one predetermined interval.
- the method comprising;
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11. A circuit for detecting movements through a micro-electric-mechanical sensor having a fixed body and a moving mass, forming first and second detection capacitors, connected to a common node and to first and second detection nodes, respectively and having a common detection rest capacitance;
- the circuit comprising;
detection amplifying means, having inputs connected to said first and second detection capacitor, respectively and an output supplying an output voltage related to a voltage present on said common node;
a feedback stage, connected to said first and second detection node and generating a feedback voltage, maintaining said first and second detection node at a constant common mode voltage; and
a compensating stage, receiving said feedback voltage and feeding said common node with a compensating electric quantity, inversely proportional to said common detection rest capacitance in at least one predetermined interval. - View Dependent Claims (12, 13, 14, 15, 16)
- the circuit comprising;
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17. A method for compensating for effects of spurious movements of an electro-mechanical sensor in a detection circuit, comprising:
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comparing capacitances of first and second detection capacitors formed between a moving mass of the electro-mechanical sensor and a fixed body of the sensor, wherein the moving mass is a common node of the first and second capacitors;
measuring a common detection capacitance of the sensor; and
introducing a compensation voltage, inversely proportionate to the common detection capacitance, to the common node of the sensor. - View Dependent Claims (18, 19)
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20. A device, comprising:
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an electro-mechanical sensor having a movable mass and a fixed body, configured to detect motion in a first axis and including first and second detection capacitors formed between the movable mass and the fixed body, the movable mass being a common node of the first and second capacitors;
a first circuit, configured to compare capacitances of the first and second capacitors and provide an output voltage proportionate to a difference of the capacitances; and
a second circuit, configured to supply a compensation voltage to the common node, inversely proportionate to a common capacitance of the sensor. - View Dependent Claims (21, 22, 23)
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24. A method for operating an electro-mechanical sensor in a detection circuit, comprising:
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detecting a change in capacitance of first and second detection capacitors formed between a movable mass of the sensor and a fixed body of the sensor;
providing, during the detecting step, an output value proportionate to a capacitive unbalance between the first and second detection capacitors;
storing, during the detecting step, a value corresponding to a on detection capacitance of the sensor; and
compensating, in the detection circuit, and during the detecting step, for changes in the common detection capacitance. - View Dependent Claims (25, 26)
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Specification