Methods and systems for detecting a capacitance using switched charge transfer techniques
First Claim
1. A method for measuring a measurable capacitance, the method comprising the steps of:
- performing a first charge transfer process for a first number of times equal to at least two, wherein the first charge transfer process comprises the steps of;
applying a first voltage to the measurable capacitance; and
allowing the measurable capacitance to share charge through a passive impedance with a filter capacitance, wherein the passive impedance remains coupled to both the measurable capacitance and the filter capacitance throughout the applying and allowing steps of the first charge transfer process;
performing a second charge transfer process for a second number of times equal to at least one, wherein the second charge transfer process comprises the steps of;
applying a second voltage to the measurable capacitance; and
allowing the measurable capacitance to share charge with the filter capacitance through the passive impedance, wherein the first voltage transfers charge in a first direction, and the second voltage transfers charge in a second direction opposite the first direction, and wherein the passive impedance remains coupled to both the measurable capacitance and the filter capacitance throughout the applying and allowing steps of the second charge transfer process; and
determining a value of the measurable capacitance from the first charge transfer process and the second charge transfer process.
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Accused Products
Abstract
Methods, systems and devices are described for detecting a measurable capacitance using charge transfer techniques. According to various embodiments, a charge transfer process is performed for two or more times. During the charge transfer process, a pre-determined voltage is applied to the measurable capacitance, and the measurable capacitance is then allowed to share charge with a filter capacitance through a passive impedance that remains coupled to both the measurable capacitance and to the filter capacitance throughout the charge transfer process. The value of the measurable capacitance can then be determined as a function of a representation of a charge on the filter capacitance and the number of times that the charge transfer process was performed. 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 an input sensor.
98 Citations
26 Claims
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1. A method for measuring a measurable capacitance, the method comprising the steps of:
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performing a first charge transfer process for a first number of times equal to at least two, wherein the first charge transfer process comprises the steps of; applying a first voltage to the measurable capacitance; and allowing the measurable capacitance to share charge through a passive impedance with a filter capacitance, wherein the passive impedance remains coupled to both the measurable capacitance and the filter capacitance throughout the applying and allowing steps of the first charge transfer process; performing a second charge transfer process for a second number of times equal to at least one, wherein the second charge transfer process comprises the steps of; applying a second voltage to the measurable capacitance; and allowing the measurable capacitance to share charge with the filter capacitance through the passive impedance, wherein the first voltage transfers charge in a first direction, and the second voltage transfers charge in a second direction opposite the first direction, and wherein the passive impedance remains coupled to both the measurable capacitance and the filter capacitance throughout the applying and allowing steps of the second charge transfer process; and determining a value of the measurable capacitance from the first charge transfer process and the second charge transfer process. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A proximity sensor comprising:
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a sensor electrode having a measurable capacitance; a switch coupled to the measurable capacitance; a passive network coupled to the measurable capacitance and the switch, the passive network comprising a passive impedance and a filter capacitance, wherein the passive impedance statically couples the measurable capacitance to the filter capacitance; and a controller coupled to the switch, wherein the controller is configured to perform a first charge transfer process for a first number of times equal to at least two and a second charge transfer process for a second number of times equal to at least one, wherein the first charge transfer process comprises; applying a first voltage to the measurable capacitance; and allowing the measurable capacitance to share charge through a passive impedance with a filter capacitance, wherein the passive impedance remains coupled to both the measurable capacitance and the filter capacitance throughout the applying and allowing of the first charge transfer process; and wherein the second charge transfer process comprises; applying a second voltage to the measurable capacitance; and allowing the measurable capacitance to share charge with the filter capacitance through the passive impedance, wherein the first voltage transfers charge in a first direction, and the second voltage transfers charge in a second direction opposite the first direction, and wherein the passive impedance remains coupled to both the measurable capacitance and the filter capacitance throughout the applying and allowing of the second charge transfer process; and and wherein the controller is further configured to determine a value of the measurable capacitance from the first charge transfer process and the second charge transfer process. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A proximity sensor comprising:
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a sensor electrode having a measurable capacitance; a switch coupled to the sensor electrode; a passive network coupled to the sensor electrode and the switch, the passive network comprising a passive impedance and a filter capacitance, wherein the passive impedance statically couples the sensor electrode to the filter capacitance; and a controller coupled to the switch, wherein the controller is configured to perform a charge transfer process for a number of times greater than one, wherein the charge transfer process comprises applying a pre-determined voltage to the measurable capacitance using the switch and allowing the measurable capacitance to share charge with the filter capacitance through the passive impedance, and wherein the controller is further configured to determine a voltage of the filter capacitance and determine a value of the measurable capacitance as a function of the voltage of the filter capacitance. - View Dependent Claims (21, 22, 23, 24, 25, 26)
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Specification