Methods and systems for detecting a capacitance using sigma-delta measurement techniques
First Claim
1. An electric circuit for measuring a capacitance value, the electric circuit comprising:
- a first switch coupled to a first capacitance;
an integrating capacitance coupled to the first capacitance, wherein the integrating capacitance is configured to accumulate charge received from the first capacitance;
a charge changing circuit coupled to the integrating capacitance; and
a controller configured to measure the capacitance value by repeatedly applying a voltage to the first capacitance using the first switch, repeatedly accumulating charge received from the first capacitance on the integrating capacitance, and repeatedly changing a charge on the integrating capacitance using the charge changing circuit in response to a voltage on the integrating capacitance being past a threshold of a quantizer.
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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
27 Claims
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1. An electric circuit for measuring a capacitance value, the electric circuit comprising:
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a first switch coupled to a first capacitance; an integrating capacitance coupled to the first capacitance, wherein the integrating capacitance is configured to accumulate charge received from the first capacitance; a charge changing circuit coupled to the integrating capacitance; and a controller configured to measure the capacitance value by repeatedly applying a voltage to the first capacitance using the first switch, repeatedly accumulating charge received from the first capacitance on the integrating capacitance, and repeatedly changing a charge on the integrating capacitance using the charge changing circuit in response to a voltage on the integrating capacitance being past a threshold of a quantizer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. 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; 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 based on the quantized values using the charge changing circuit, and determining the capacitance value of the measurable capacitance from the quantized values. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for determining a capacitance value, the method comprising the steps of:
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applying a voltage to the first capacitance using a first switch; allowing the first capacitance to share charge with an integrating capacitance; outputting a quantized value reflective of whether the voltage on the integrating capacitance is past a threshold of a quantizer; changing a charge on the integrating capacitance by an amount of charge responsive to the voltage on the integrating capacitance being past the threshold of the quantizer, wherein the amount of charge is determined at least in part as a function of the quantized value outputted by the quantizer; repeating each of the applying step, the allowing step, the outputting, and the changing step at least once to generate a plurality of quantized values; and determining the capacitance value using the plurality of quantized values generated by the repeating step. - View Dependent Claims (22, 23, 24, 25, 26, 27)
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Specification