Microchip Technology

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  • 3-Channel Capacitive Touch Sensing Circuit

  • Created: May 27, 2016

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The consumer electronics device is now into capacitive touch button or in soft touch technology, since it brings simplicity and elegance to our electronic devices nowadays. In this design, it features capacitive touch sensor controller that is capable of three capacitive touch sensor inputs, proximity detection, and signal guard. It supports multiple button pattern detection, power button, and press and hold features for volume-like application.

The circuit is comprised of CAP1293-1-AC3 with few external components. The CAP1293-1-AC3 is the 3-channel capacitive touch sensor controller in which each sensor input is calibrated to compensate for systems parasitic capacitance and automatically recalibrated to compensate for gradual environmental changes. The touch button should determine the sensor input that can be done through program configuration and sensor controller calibration. The proximity sensor works almost the same with the touch button in which the sensor input is configured to detect changes in capacitance due to proximity of a touch. The circuitry to this proximity sensor detects the change of capacitance that is generated as an object approaches, but does not physically touch, the enabled sensor pad(s). The sensor inputs used to detect proximity have physically larger pads than standard buttons. The MCU is the embedded controller that supports I2C data communications. The capacitors act as the filters in the supply while the resistors are for pull-up in the I2C communications.

The design is applicable for small or DIY projects. The capacitive touch sensor controller can be part of large circuit board of consumer electronics that can add features. It is also LCD monitors, Notebook PCs, and Desktop PCs.



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