METHODS AND SYSTEMS FOR SIGMA DELTA CAPACITANCE MEASURING USING SHARED COMPONENTS
First Claim
1. A system for measuring a plurality of measurable capacitances, the system comprising:
- at least one passive network coupled to 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 coupled to the plurality of measurable capacitances, wherein the controller is configured to perform, for each of the plurality of measurable capacitances, a charge transfer measurement process comprising;
repeatedly applying an associated voltage to the measurable capacitance using an associated digital output in the plurality of digital outputs,accumulating charge on an associated passive network of the at least one passive network by repeatedly sharing charge between the measurable capacitance and the associated passive network,generating quantized values by repeatedly measuring a voltage on the associated passive network using a quantizer having at least one threshold,repeatedly changing charge on the associated passive network by a quantized amount of charge using an associated charge changing circuit of the at least one charge changing circuit, the quantized amount of charge based on the quantized values, anddigitally filtering the quantized values.
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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.
28 Citations
21 Claims
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1. A system for measuring a plurality of measurable capacitances, the system comprising:
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at least one passive network coupled to 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 coupled to the plurality of measurable capacitances, wherein the controller is configured to perform, for each of the plurality of measurable capacitances, a charge transfer measurement process comprising; repeatedly applying an associated voltage to the measurable capacitance using an associated digital output in the plurality of digital outputs, accumulating charge on an associated passive network of the at least one passive network by repeatedly sharing charge between the measurable capacitance and the associated passive network, generating quantized values by repeatedly measuring a voltage on the associated passive network using a quantizer having at least one threshold, repeatedly changing charge on the associated passive network by a quantized amount of charge using an associated charge changing circuit of the at least one charge changing circuit, the quantized amount of charge based on the quantized values, and digitally filtering the quantized values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A controller comprising:
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a plurality of digital outputs; and a memory, the memory including executable instructions to perform, for each of a plurality of measureable capacitances, a charge transfer measurement process comprising; repeatedly applying an associated voltage to the measurable capacitance using a digital output in the plurality of digital outputs; accumulating charge on an associated passive network by repeatedly sharing charge from the measurable capacitance; generating quantized values by repeatedly measuring a voltage on the associated passive network using a quantizer having at least one threshold; repeatedly changing a charge on the associated passive network by a quantized amount of charge, the quantized amount of charge based on the quantized values; and digitally filtering the quantized values to determine a measure of the measurable capacitance. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A method of measuring a plurality of measurable capacitances, the method comprising:
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repeatedly applying a first voltage to a first measurable capacitance using a first switch; accumulating charge on a passive network by repeatedly sharing charge between the first measurable capacitance and the passive network; generating first quantized values by repeatedly measuring a voltage on the passive network using a quantizer having at least one threshold; repeatedly changing charge in the passive network by a quantized amount of charge based on the first quantized values; digitally filtering the first quantized values; repeatedly applying a second voltage to a second measurable capacitance using a second switch; accumulating charge on the passive network by repeatedly sharing charge between the second measurable capacitance and the passive network; generating second quantized values by repeatedly measuring a voltage on the second passive network using at least one of the quantizer and a second quantizer, repeatedly changing charge in the second passive network by a second quantized amount of charge based on the second quantized values; and digitally filtering the second quantized values.
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Specification