Servo techniques for approximation of differential capacitance of a sensor
First Claim
1. A device for approximating a difference between two capacitive components, comprising:
- a first capacitive component and a second capacitive component;
a capacitance approximation bank including a plurality of approximation capacitors;
a capacitance adjustment module configured to connect one or more of the approximation capacitors in parallel with one of the first and second capacitive components;
a memory location for storage of an indication of a first set of approximation capacitors that was previously connected in a preceding approximation test;
a control module that identifies the smaller of the first and second capacitive components, that identifies the larger of the first and second capacitive components, that retrieves the indication of the first set of approximation capacitors and connects the one or more capacitors of the first set of capacitors to the smaller capacitive component, and computes a variation between the value of the larger capacitive component and the value of the smaller capacitive component connected to the first set of approximation capacitors, wherein the difference between the first and second capacitive components is determined to be equivalent to the value of the first set of approximation capacitors in response to the variation being less than or equal to a first predefined value.
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Abstract
Techniques and circuits are described for approximation of the differential capacitance of a capacitive sensor to, among other things, optimize device operation and power consumption. In particular, feedback techniques are utilized for measurement and approximation of the differential capacitance of the capacitive sensor. In accordance with the disclosure, the capacitance approximation value for a test cycle preceding a given test cycle is utilized to reduce the number of iterations to be performed in a continuous series of test cycles. The capacitance approximation value for the given test cycle is reported as being equivalent to that of the preceding test cycle if the variance between the selected capacitance and the unselected capacitance is less than or equal to a first predefined value.
80 Citations
26 Claims
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1. A device for approximating a difference between two capacitive components, comprising:
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a first capacitive component and a second capacitive component; a capacitance approximation bank including a plurality of approximation capacitors; a capacitance adjustment module configured to connect one or more of the approximation capacitors in parallel with one of the first and second capacitive components; a memory location for storage of an indication of a first set of approximation capacitors that was previously connected in a preceding approximation test; a control module that identifies the smaller of the first and second capacitive components, that identifies the larger of the first and second capacitive components, that retrieves the indication of the first set of approximation capacitors and connects the one or more capacitors of the first set of capacitors to the smaller capacitive component, and computes a variation between the value of the larger capacitive component and the value of the smaller capacitive component connected to the first set of approximation capacitors, wherein the difference between the first and second capacitive components is determined to be equivalent to the value of the first set of approximation capacitors in response to the variation being less than or equal to a first predefined value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method of performing an approximation test of a difference between two capacitive components, the approximation test comprising:
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obtaining a first value of a first capacitive component; obtaining a second value of a second capacitive component; comparing the first value to the second value, wherein the result of the comparison identifies the smaller of the first and second values corresponding to the smaller of the first and second capacitive component and identifies the larger of the first and second values corresponding to the larger of the first and second capacitive component; connecting a first set of approximation capacitors to the identified smaller capacitive component in parallel responsive to the difference between the first value and the second value exceeding a predetermined value, wherein the first set of approximation capacitors include the capacitors previously connected in a preceding approximation test; computing a variation between the value of the larger capacitive component and the combined value associated with the smaller capacitive component and the first set of approximation capacitors; and determining the difference between the first and second capacitive components to be equivalent to the value of the first set of approximation capacitors in response to the variation being less than a predefined value. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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Specification