Methods and systems for detecting a capacitance using sigma-delta measurement techniques
First Claim
1. An electrical circuit for measuring a capacitance value, the electrical circuit comprising:
- a first switch coupled to a first capacitance;
a passive network coupled to the first capacitance, wherein the passive network is configured to store charge received from the first capacitance;
a charge changing circuit coupled to the passive network; and
a controller configured to measure the capacitance value by repeatedly applying a voltage to the first capacitance using the first switch, repeatedly storing charge received from the first capacitance on the passive network, and repeatedly changing a charge on the passive network by a quantized amount of charge using the charge changing circuit in response to a voltage on the passive network being past a threshold of a quantizer, the quantized amount of charge determined at least in part as a function of an output of the quantizer.
3 Assignments
0 Petitions
Accused Products
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.
-
Citations
36 Claims
-
1. An electrical circuit for measuring a capacitance value, the electrical circuit comprising:
-
a first switch coupled to a first capacitance; a passive network coupled to the first capacitance, wherein the passive network is configured to store charge received from the first capacitance; a charge changing circuit coupled to the passive network; and a controller configured to measure the capacitance value by repeatedly applying a voltage to the first capacitance using the first switch, repeatedly storing charge received from the first capacitance on the passive network, and repeatedly changing a charge on the passive network by a quantized amount of charge using the charge changing circuit in response to a voltage on the passive network being past a threshold of a quantizer, the quantized amount of charge determined at least in part as a function of an output of the quantizer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
-
-
23. A system for measuring a plurality of measurable capacitances in a proximity sensor, the system comprising:
-
a passive network coupled to the plurality of measurable capacitances, the passive network comprising an integrating capacitance, the integrating capacitance configured to store charge received from the plurality of measurable capacitances; a charge changing circuit coupled to the passive network; and a controller, the controller including a plurality of digital outputs, each of the plurality of measurable capacitances coupled to an associated digital output in the plurality of digital outputs, the controller configured to measure each of the plurality of measurable capacitances by, for each measurable capacitance in the plurality of measurable capacitances, repeatedly applying a predetermined voltage to the measurable capacitance using the associated digital output, repeatedly sharing charge between the measurable capacitance and the passive network to accumulate charge on the integrating capacitance, repeatedly measuring a voltage on the passive network using an analog-to-digital converter 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 a value for the measurable capacitance by digitally filtering the quantized values. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
-
Specification