NXP capacitive touch switches for harsh environments

Using digital signal processing to detect changes in capacitance on a remote sensing plate, NXP’s capacitive touch switches eliminate the need for a microcontroller and firmware for post-processing. With very low power consumption – typically 3 μA per channel – NXP’s capacitive touch and proximity switches can also run continuously, with no complicated power-down and wake-up schemes required.

The sampling frequency and response times are easily adjustable, allowing designers to configure the PCF8883, PCF8885, PCA8885 and PCA8886 for a wide range of industrial and automotive applications. The single-channel PCF8883 and dual-channel PCA8886 can be used as touch switches, or as proximity sensors which wake up and reactivate the system from power-down mode. The multi-channel PCF8885 can be used as a slider, as a rotary wheel and for dedicated touch keys.

NXP’s highly robust capacitive touch and proximity switches are ideal for applications using touch screen control panels, including:

• Home appliances such as washing machines, ovens and vacuum cleaners,
• Building control systems for heating, ventilation and air conditioning and lighting,
• Industrial equipment such as automated teller machines,
• Medical devices such as blood pressure monitors,
• Automotive applications such as climate control units, car entertainment systems, car access systems, and mirror and sun-roof control units.

"Thanks to smartphones, consumers have come to expect the convenience of touch screens to control a whole host of other devices. With our self-calibrating capacitive touch and proximity switches, NXP is making it straightforward for leading appliance makers, automotive suppliers and other equipment manufacturers to bring touch controls and LCD displays together – with minimal overhead. Through extensive testing, we’ve also been able to demonstrate the robustness of our solution, even in extreme environmental conditions. With world-class LCD drivers, LED controllers, real-time clocks, GPIOs and capacitive touch sensors, NXP offers a comprehensive portfolio of very low power interface solutions that also deliver accuracy, clarity, robustness and reliability over time," commented Grahame Cooney, general manager of high-speed interfaces and clock, watches and graphic drivers, NXP Semiconductors.

Key features:

• Dynamic touch and proximity switch,
• Proprietary digital signal processing method,
• Adjustable response time,
• Continuous over-life self-calibration,
• Sensing plate can be placed on a remote location – e.g. 50 cm away,
• Large temperature operating range (Tamb = -40ºC to 85ºC).