Methods and systems for sigma delta capacitance measuring using shared component
First Claim
1. A system for measuring each of a plurality of measurable capacitances, the system comprising:
- at least one passive network coupled to the plurality of measurable capacitances, each of the at least one passive network comprising at least one integrating capacitance configured to accumulate charge received from the plurality of measurable capacitances;
at least one charge changing circuit coupled to the at least one passive network; and
a controller, the controller including a plurality of digital outputs, each of the plurality of digital outputs coupled to a measurable capacitance in the plurality of measurable capacitances, the controller configured to measure each of the plurality of measurable capacitances by, for each selected measurable capacitance in the plurality of measurable capacitances, repeatedly applying a voltage to the selected measurable capacitance using a digital output in the plurality of digital outputs, repeatedly sharing charge between the selected measurable capacitance and the at least one passive network to accumulate charge on the at least one integrating capacitance, and repeatedly changing a charge on the at least one integrating capacitance by a quantized amount of charge using the at least one charge changing circuit in response to the charge on the at least one passive network being past a threshold of a quantizer, the quantized amount of charge determined at least in part as a function of an output of the quantizer.
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Abstract
Methods, systems and devices are described for detecting a measurable capacitance using sigma-delta charge transfer techniques that can be implemented with many standard microcontrollers, and can share components to reduce device complexity and improve performance. In the various implementations of this embodiment, the passive network used to accumulate charge can be shared between multiple measurable capacitances. A switch or IO controlling the charge sharing and/or charge changing can also be shared Likewise, in various implementations a voltage conditioning circuit configured to provide a variable reference voltage can be shared between multiple measurable capacitances. Finally, in various implementations a guarding electrode configured to guard the measurable capacitances can be shared between multiple measurable capacitances. In each of these cases, sharing components can reduce device complexity and improve performance.
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Citations
25 Claims
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1. A system for measuring each of a plurality of measurable capacitances, the system comprising:
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at least one passive network coupled to the plurality of measurable capacitances, each of the at least one passive network comprising at least one integrating capacitance configured to accumulate charge received from the plurality of measurable capacitances; at least one charge changing circuit coupled to the at least one passive network; and a controller, the controller including a plurality of digital outputs, each of the plurality of digital outputs coupled to a measurable capacitance in the plurality of measurable capacitances, the controller configured to measure each of the plurality of measurable capacitances by, for each selected measurable capacitance in the plurality of measurable capacitances, repeatedly applying a voltage to the selected measurable capacitance using a digital output in the plurality of digital outputs, repeatedly sharing charge between the selected measurable capacitance and the at least one passive network to accumulate charge on the at least one integrating capacitance, and repeatedly changing a charge on the at least one integrating capacitance by a quantized amount of charge using the at least one charge changing circuit in response to the charge on the at least one passive network being past a threshold of a quantizer, the quantized amount of charge determined at least in part as a function of an output of the quantizer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method for measuring each of a plurality of measurable capacitances, the method comprising the steps of:
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selecting a first measurable capacitance in the plurality of measurable capacitances, and for the first selected measurable capacitance; (A) repeatedly applying a voltage to the selected measurable capacitance using a digital output in a plurality of digital outputs; (B) repeatedly sharing charge between the selected measurable capacitance and at least one passive network to accumulate charge on at least one integrating capacitance in the at least one passive network; (C) repeatedly changing a charge on the at least one integrating capacitance by a quantized amount of charge in response to the charge on the at least one passive network being past a threshold of a quantizer, the quantized amount of charge determined at least in part as a function of an output of the quantizer; and (D) determine a measure of the selected measurable capacitance from the output of the quantizer; selecting a second measurable capacitance in the plurality of measurable capacitances, and repeating steps (A)-(D) for the second selected measurable capacitance. - View Dependent Claims (21, 22, 23, 24, 25)
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Specification