Capacitance measurement circuit with dynamic feedback
First Claim
1. A method of measuring a capacitance, comprising:
- building up charge on a first accumulator over a plurality of switch-controlled charging or discharging cycles governed by a first control signal;
partially discharging the first accumulator as a function of a second control signal, optionally using a variable current device;
monitoring an accumulator signal that is based on the charge on the first accumulator;
dynamically adjusting one of the first and second control signals so as to keep the accumulator signal in a desired range; and
using the dynamically adjusted control signal as a measure of the capacitance.
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Accused Products
Abstract
Methods, devices, and systems that measure capacitance are disclosed. Typically, an accumulator circuit couples to the capacitance and includes an accumulator and switch(es) that charge the accumulator over a series of switch-controlled charging or discharging cycles governed by a first control signal. The accumulator circuit provides an accumulator signal based on the charge on the first accumulator. A discharge circuit couples to the accumulator circuit and includes an optional variable current device, the discharge circuit partially discharging the accumulator based on a second control signal. A control circuit, which couples to the accumulator circuit and the discharge circuit, dynamically adjusts the first and/or second control signals to keep the accumulator signal in a desired range. The dynamically adjusted control signal can be used as a measure of the capacitance. Such methods and systems may be used in capacitive touch sensing devices such as capacitive buttons and capacitive touch panels.
37 Citations
24 Claims
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1. A method of measuring a capacitance, comprising:
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building up charge on a first accumulator over a plurality of switch-controlled charging or discharging cycles governed by a first control signal; partially discharging the first accumulator as a function of a second control signal, optionally using a variable current device; monitoring an accumulator signal that is based on the charge on the first accumulator; dynamically adjusting one of the first and second control signals so as to keep the accumulator signal in a desired range; and using the dynamically adjusted control signal as a measure of the capacitance. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A device for measuring a capacitance, comprising:
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an accumulator circuit coupleable to the capacitance and comprising a first accumulator and one or more switches configured to build up charge on the first accumulator over a plurality of switch-controlled charging or discharging cycles governed by a first control signal coupled to the one or more switches, the accumulator circuit adapted to provide an accumulator signal based on the charge on the first accumulator; a discharge circuit coupled to the accumulator circuit and optionally comprising a variable current device, the discharge circuit being adapted to partially discharge the first accumulator as a function of a second control signal; and a control circuit coupled to the accumulator circuit and the discharge circuit, the control circuit being adapted to dynamically adjust one of the first and second control signals so as to keep the accumulator signal in a desired range; wherein the device uses the dynamically adjusted control signal as a measure of the capacitance. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method of measuring a capacitance, comprising:
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building up charge on a first accumulator over a plurality of switch-controlled charging or discharging cycles governed by a first control signal; partially discharging the first accumulator during the plurality of switch-controlled charging or discharging cycles; monitoring an accumulator signal that is based on the charge on the first accumulator; dynamically adjusting the first control signal so as to keep the accumulator signal in a desired range; and using the dynamically adjusted control signal as a measure of the capacitance.
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24. A device for measuring a capacitance, comprising:
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an accumulator circuit coupleable to the capacitance and comprising a first accumulator and one or more switches configured to build up charge on the first accumulator over a plurality of switch-controlled charging or discharging cycles governed by a first control signal coupled to the one or more switches, the accumulator circuit adapted to provide an accumulator signal based on the charge on the first accumulator; a discharge circuit coupled to the accumulator circuit, the discharge circuit being adapted to partially discharge the first accumulator during the plurality of switch-controlled charging or discharging cycles; and a control circuit coupled to the accumulator circuit, the control circuit being adapted to dynamically adjust the first control signal so as to keep the accumulator signal in a desired range; wherein the device uses the dynamically adjusted control signal as a measure of the capacitance.
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Specification