Methods and systems for guarding a charge transfer capacitance sensor for proximity detection
First Claim
1. A device for determining a measurable capacitance for proximity detection, the device comprising:
- a plurality of sensing electrodes;
a guarding electrode proximate the plurality of sensing electrodes;
a passive network that includes a filter capacitance; and
a controller coupled to the plurality of sensing electrodes, the guarding electrode, and the passive network, the controller configured to apply a pre-determined voltage to at least one of the plurality of sensing electrodes using a first switch, apply a first guard voltage to the at least one guarding electrode using a second switch, share charge between at least one of the plurality of sensing electrodes and the passive network such that shared charge is accumulated on the filter capacitance, apply a second guard voltage different from the first guard voltage to the guarding electrode; and
measure a voltage on the filter capacitance for a number of measurements equal to at least one to produce at least one result to determine the measurable capacitance for proximity detection.
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Accused Products
Abstract
Methods, systems and devices are described for determining a measurable capacitance for proximity detection in a sensor having a plurality of sensing electrodes and at least one guarding electrode. A charge transfer process is executed for at least two executions. The charge transfer process includes applying a pre-determined voltage to at least one of the plurality of sensing electrodes using a first switch, applying a first guard voltage to the at least one guarding electrode using a second switch, sharing charge between the at least one of the plurality of sensing electrodes and a filter capacitance, and applying a second guard voltage different from the first guard voltage to the at least one guarding electrode. A voltage is measured on the filter capacitance for a number of measurements equal to at least one to produce at least one result to determine the measurable capacitance for proximity detection.
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Citations
25 Claims
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1. A device for determining a measurable capacitance for proximity detection, the device comprising:
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a plurality of sensing electrodes; a guarding electrode proximate the plurality of sensing electrodes; a passive network that includes a filter capacitance; and a controller coupled to the plurality of sensing electrodes, the guarding electrode, and the passive network, the controller configured to apply a pre-determined voltage to at least one of the plurality of sensing electrodes using a first switch, apply a first guard voltage to the at least one guarding electrode using a second switch, share charge between at least one of the plurality of sensing electrodes and the passive network such that shared charge is accumulated on the filter capacitance, apply a second guard voltage different from the first guard voltage to the guarding electrode; and
measure a voltage on the filter capacitance for a number of measurements equal to at least one to produce at least one result to determine the measurable capacitance for proximity detection. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A device for measuring a capacitance value, the device comprising:
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a passive network coupled to a 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; a guarding electrode proximate the first capacitance; a controller configured to measure the capacitance value by repeatedly applying a predetermined voltage to the first capacitance, repeatedly storing charge received from the first capacitance on the passive network, and repeatedly comparing a voltage on the passive network to a threshold of a quantizer and changing a charge on the passive network by a quantized amount of charge using the charge changing circuit in response to the voltage on the passive network being past the threshold of the quantizer, the quantized amount of charge determined at least in part as a function of an output of the quantizer; and
wherein the controller is configured to apply a guarding signal to the guarding electrode, the guarding signal including at least a first guard voltage level and a second guard voltage level. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A device for measuring a measurable capacitance, the device comprising:
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a filter capacitance; a passive impedance statically coupling the filter capacitance to the measurable capacitance; a guarding electrode proximate the measurable capacitance; and a controller coupled to the measurable capacitance, wherein the controller is configured to perform a charge transfer process, wherein the charge transfer process comprises applying a predetermined voltage to the measurable capacitance 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 value of the measurable capacitance as a function of an accumulated charge on the filter capacitance; and
wherein the controller is configured to apply a guarding signal to the guarding electrode, the guarding signal including at least a first guard voltage level and a second guard voltage level. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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Specification