Capacitance sensing circuits
First Claim
1. A capacitance sensing circuit comprising:
- a buffer circuit coupled to an external capacitor through a touch-sensing pad and including a pull-up device and a pull-down device;
a modulation circuit including a first current mirror device having a current drivability corresponding to one Nth (where “
N”
denotes a positive real number) a current drivability of the pull-up device and a second current mirror device having a current drivability corresponding to one Nth a current drivability of the pull-down device; and
an integral circuit configured to integrate voltage values at an output node of the modulation circuit to output the integrated voltage values,wherein the pull-up device and the first current mirror device constitute a current mirror circuit, and the pull-down device and the second current mirror device constitute another current mirror circuit.
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Accused Products
Abstract
A capacitance sensing circuit includes a buffer circuit, a modulation circuit, and an integral circuit. The buffer circuit is coupled to an external capacitor through a touch-sensing pad, and includes a pull-up device and a pull-down device. The modulation circuit includes a first current mirror device having a current drivability corresponding to one Nth (where “N” denotes a positive real number) a current drivability of the pull-up device and a second current mirror device having a current drivability corresponding to one Nth a current drivability of the pull-down device. The integral circuit integrates voltage values at an output node of the modulation circuit to output the integrated voltage values. The pull-up device and the first current mirror device constitute a current mirror circuit, and the pull-down device and the second current mirror device constitute another current mirror circuit.
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Citations
23 Claims
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1. A capacitance sensing circuit comprising:
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a buffer circuit coupled to an external capacitor through a touch-sensing pad and including a pull-up device and a pull-down device; a modulation circuit including a first current mirror device having a current drivability corresponding to one Nth (where “
N”
denotes a positive real number) a current drivability of the pull-up device and a second current mirror device having a current drivability corresponding to one Nth a current drivability of the pull-down device; andan integral circuit configured to integrate voltage values at an output node of the modulation circuit to output the integrated voltage values, wherein the pull-up device and the first current mirror device constitute a current mirror circuit, and the pull-down device and the second current mirror device constitute another current mirror circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A capacitance sensing circuit comprising:
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a buffer circuit coupled to an external capacitor through a touch-sensing pad and including a pull-up device and a pull-down device; a first modulation circuit including a first current mirror device having a current drivability corresponding to one Nth (where “
N”
denotes a positive real number) a current drivability of the pull-up device and a second current mirror device having a current drivability corresponding to one Nth a current drivability of the pull-down device, the pull-up device and the first current mirror device constituting a current mirror circuit, the pull-down device and the second current mirror device constituting another current mirror circuit;a second modulation circuit including a third current mirror device having a current drivability corresponding to one Nth a current drivability of the pull-up device and a first diode-connected device coupled between the third current mirror device and a ground voltage terminal, the pull-up device and the third current mirror device constituting a current mirror circuit; a third modulation circuit including a fourth current mirror device having a current drivability corresponding to one Nth a current drivability of the pull-down device and a second diode-connected device coupled between a power supply voltage terminal and the fourth current mirror device, the pull-down device and the fourth current mirror device constituting a current mirror circuit; a fourth modulation circuit including a fifth current mirror device and a sixth current mirror device, the second diode-connected device and the fifth current mirror device constituting one current mirror circuit, the first diode-connected device and the sixth current mirror device constituting another current mirror circuit; an integral circuit configured to integrate voltage values at one of output nodes of the first and fourth modulation circuits to output the integrated voltage values; and a switch configured to electrically connect one of the output nodes of the first and fourth modulation circuits to the integral circuit. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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Specification