Methods and systems for detecting a capacitance using sigma-delta measurement techniques
First Claim
1. A system for determining a capacitance value of a measurable capacitance, the system comprising:
- an integrating capacitance configured to store charge received from the measurable capacitance;
a charge changing circuit coupled to the integrating capacitance, the charge changing circuit including at least one delta capacitance; and
a controller configured to determine the capacitance value by repeatedly applying a predetermined voltage to the measurable capacitance, repeatedly sharing charge between the measurable capacitance and the integrating capacitance to accumulate charge on the integrating capacitance, repeatedly measuring a voltage on the integrating capacitance using a quantizer of the controller and generating quantized values responsive to the repeated measurings, repeatedly changing charge on the integrating capacitance by a quantized amount of charge based on the quantized values using the delta capacitance in the charge changing circuit, and determining the capacitance value of the measurable capacitance 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.
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Citations
25 Claims
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1. A system for determining a capacitance value of a measurable capacitance, the system comprising:
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an integrating capacitance configured to store charge received from the measurable capacitance; a charge changing circuit coupled to the integrating capacitance, the charge changing circuit including at least one delta capacitance; and a controller configured to determine the capacitance value by repeatedly applying a predetermined voltage to the measurable capacitance, repeatedly sharing charge between the measurable capacitance and the integrating capacitance to accumulate charge on the integrating capacitance, repeatedly measuring a voltage on the integrating capacitance using a quantizer of the controller and generating quantized values responsive to the repeated measurings, repeatedly changing charge on the integrating capacitance by a quantized amount of charge based on the quantized values using the delta capacitance in the charge changing circuit, and determining the capacitance value of the measurable capacitance by digitally filtering the quantized values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system for determining a capacitance value of a measurable capacitance, the system comprising:
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an integrating capacitance configured to store charge received from the measurable capacitance; a charge changing circuit coupled to the integrating capacitance, the charge changing circuit including an array of delta capacitances; and a controller configured to determine the capacitance value by repeatedly applying a predetermined voltage to the measurable capacitance, repeatedly sharing charge between the measurable capacitance and the integrating capacitance to accumulate charge on the integrating capacitance, repeatedly measuring a voltage on the integrating capacitance using a quantizer of the controller and generating quantized values responsive to the repeated measurings, repeatedly changing charge on the integrating capacitance by a quantized amount of charge using a selected portion of the array of delta capacitance in the charge changing circuit, the selected portion of the array based on the quantized values, and determining the capacitance value of the measurable capacitance by digitally filtering the quantized values. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. A method for measuring a measurable capacitance, the method comprising the steps of:
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applying a voltage to the measurable capacitance using a first switch; allowing the measurable capacitance to share charge with an integrating capacitance; changing a charge on the integrating capacitance by a quantized amount of charge if the voltage on the integrating capacitance is past a threshold of a quantizer, the quantized amount of charge determined at least in part as a function of a quantized value outputted by the quantizer; repeating each of the applying step, the allowing step, and the changing step at least once, wherein the repeating maintains the voltage on the integrating capacitance near the threshold of the quantizer; and filtering the quantized values outputted by the quantizer to provide a measure of the measurable capacitance. - View Dependent Claims (21, 22, 23, 24, 25)
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Specification