Methods and systems for detecting a capacitance using sigma-delta measurement techniques
First Claim
1. A system for determining a capacitance value, the system comprising:
- a first switch coupled to a first capacitance;
a passive network coupled to the first capacitance, wherein the passive network includes an integrating capacitance configured to store charge received from the first capacitance;
a charge changing circuit coupled to the passive network; and
a controller configured to determine the capacitance value by repeatedly applying a predetermined voltage to the first capacitance using the first switch, repeatedly sharing charge between the first capacitance and the passive network to accumulate charge on the integrating capacitance, repeatedly measuring a voltage on the passive network using a quantizer having at least one threshold and generating quantized values responsive to the repeated measurings, repeatedly changing the charge on the integrating capacitance by a quantized amount of charge based on the quantized values using the charge changing circuit, and determining the capacitance value by digitally filtering the quantized values.
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Abstract
Methods, systems and devices are described for detecting a measurable capacitance using sigma-delta measurement techniques. According to various embodiments, a voltage is applied to the measurable capacitance using a first switch. The measurable capacitance is allowed to share charge with a passive network. If the charge on the passive network is past a threshold value, then the charge on the passive network is changed by a known amount for a sufficient number of repetitions until the measurable capacitance can be detected. Such a detection scheme may be readily implemented using conventional components, and can be particularly useful in sensing the position of a finger, stylus or other object with respect to a button, slider, touchpad or other input sensor.
65 Citations
18 Claims
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1. A system for determining a capacitance value, the system comprising:
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a first switch coupled to a first capacitance; a passive network coupled to the first capacitance, wherein the passive network includes an integrating capacitance configured to store charge received from the first capacitance; a charge changing circuit coupled to the passive network; and a controller configured to determine the capacitance value by repeatedly applying a predetermined voltage to the first capacitance using the first switch, repeatedly sharing charge between the first capacitance and the passive network to accumulate charge on the integrating capacitance, repeatedly measuring a voltage on the passive network using a quantizer having at least one threshold and generating quantized values responsive to the repeated measurings, repeatedly changing the charge on the integrating capacitance by a quantized amount of charge based on the quantized values using the charge changing circuit, and determining the capacitance value by digitally filtering the quantized values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification