MULTIPLE CAPACITIVE (BUTTON) SENSOR WITH REDUCED PINOUT
First Claim
Patent Images
1. An electronic touch sensor device comprising:
- a control circuit;
at least one light emitting diode (LED) having a first electrode and a second electrode;
at least one input/output circuit operatively connected to the control circuit and comprising;
a capacitive sense circuit configured to detect a change in capacitance when an object approaches the touch sensor device, wherein the capacitive sense circuit is selectively disabled and enabled by the control circuit;
an LED driver circuit configured to drive the first electrode of the at least one LED, wherein the LED driver circuit is selectively enabled and disabled by the control circuit;
wherein the LED driver circuit is disabled when the capacitive sense circuit is enabled, and wherein the LED driver circuit is enabled when the capacitive sense circuit is disabled; and
a bias driver circuit configured to drive the second electrode of the at least one LED.
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Abstract
A capacitive touch sensor and LED driver device achieves a reduction in pin count by multiplexing LED drive functionality and capacitive sense functionality on each input/output pin. A control circuit switches between LED drive mode and capacitive sense mode at a frequency of approximately 200 Hz, although other switching frequencies can be used. A bias driver functions as a current sink for LEDs in LED drive mode and can also be used to drive a bias voltage to the LEDs during capacitive sense mode to improve noise immunity.
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Citations
17 Claims
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1. An electronic touch sensor device comprising:
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a control circuit; at least one light emitting diode (LED) having a first electrode and a second electrode; at least one input/output circuit operatively connected to the control circuit and comprising; a capacitive sense circuit configured to detect a change in capacitance when an object approaches the touch sensor device, wherein the capacitive sense circuit is selectively disabled and enabled by the control circuit; an LED driver circuit configured to drive the first electrode of the at least one LED, wherein the LED driver circuit is selectively enabled and disabled by the control circuit; wherein the LED driver circuit is disabled when the capacitive sense circuit is enabled, and wherein the LED driver circuit is enabled when the capacitive sense circuit is disabled; and a bias driver circuit configured to drive the second electrode of the at least one LED. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An electronic touch sensor device comprising:
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a control circuit; N light emitting diodes (LEDs), wherein N is an integer greater than one; and wherein each of the N LEDs has a first electrode and a second electrode; N input/output circuits, each operatively connected to the control circuit and each comprising; a capacitive sense circuit configured to detect a change in capacitance when an object approaches the touch sensor device, wherein the capacitive sense circuit is selectively disabled and enabled by the control circuit; an LED driver circuit configured to drive the first electrode of one of the N LEDs, wherein the LED driver circuit is selectively enabled and disabled by the control circuit, wherein; an output of the LED driver circuit, an input of the capacitive sense circuit, and the first electrode of one of the N LEDs all connect to a common node; and the LED driver circuit is disabled when the capacitive sense circuit is enabled, and the LED driver circuit is enabled when the capacitive sense circuit is disabled; and a bias driver circuit configured to drive the second electrode of each of the N LEDs. - View Dependent Claims (9, 10, 11, 12, 13)
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14. In an electronic touch sensor device comprising a control circuit;
- N input/output circuits each comprising an LED driver circuit and a capacitive sense circuit; and
a bias driver circuit;
a method of multiplexing capacitive sensing functionality and LED driving functionality comprises the steps of;during a drive-off portion of an operational cycle; disabling the LED driver circuit of each of the N input/output circuits; and enabling the capacitive sense circuit of each of the N input/output circuits; and during a drive-on portion of the operational cycle; enabling the LED driver circuit of each of the N input/output circuits; and disabling the capacitive sense circuit of each of the N input/output circuits. - View Dependent Claims (15, 16, 17)
- N input/output circuits each comprising an LED driver circuit and a capacitive sense circuit; and
Specification