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Flexing into future: Optimising touch sensing tech for broader markets

Posted: 07 Oct 2014 ?? ?Print Version ?Bookmark and Share

Keywords:projected-capacitive touch solutions? smartphones? Microchip?

Editor's Note: Many consumer products are now using multi-touch and gestures, but the touch sensing technology still has a long way to go before it can expand into other markets. Carol Crawford, director for touch screen controllers at Microchip Technology, and Charlie Riegert, product manager of touch screen controller group, lists the challenges that projected-capacitive touch sensing technology needs to overcome.

Projected-capacitive touch sensing technology is rapidly evolving to meet the advanced user-interface needs of modern applications. Popular consumer products that use multi-touch and gestures have fuelled an increased demand for projected-capacitive touch solutions beyond these applications. People expect to interact with most devices in the same manner as their smartphones and tablets. The challenge is that not all applications can afford the hardware, software and power budget associated with the current smartphone-optimised designs.

Applications such as security control panels, keypads, thermostats, gaming devices, remote controls and wearables have very different requirements with regard to response time, number of touches, power consumption and cost. The ability to optimise the touch controller and sensor solution to meet these requirements is crucial for the industry to expand beyond the main consumer applications.

One of the primary challenges of expanding projected-capacitive sensing technology into other markets is power consumption. The relatively high power consumption of most touch applications has limited their adoption in low-power input devices. Most embedded devices have user expectations for battery life measured in months and years, not hours like our current mobile devices. Power-consumption requirements and management become critical during the evaluation of projected-capacitive technology. The optimal combination of PCAP code with extreme low power management has enabled customers to address these power constraints while adding the PCAP touch and gesture functionality.

As an example, single-touch tap, swipe, swipe and hold, and double-tap gestures can be deployed using low-power and inexpensive electronics solutions. Performance data for a small 1in X 2in sensor running at 2V can have low power usage of ~15?A in an active idle mode, waiting for a touch and only 150?A for active scanning. In a recent design win, this translated into a more than two-year battery life. Remote controls, gaming controls and other power-conscious devices can benefit from these advancements in PCAP technology and power management. As with all applications, there are sometimes performance trade-offs, but power, size and other characteristics can be managed to meet the low-power design requirements.

Flexibility is the next challenge to expanding projected-capacitive touch sensing into new markets. The rapidly emerging market trend of incorporating touch and gestures into a wide range of devices outside the traditional mobile market requires customers to also move quickly to keep up with competition. The resulting fast design cycles require progressive and flexible PCAP touch controllers and sensor design options.

Traditional PCAP solutions have long design cycles with rigid implementations, consisting of an ASIC-style touch controller and fixed sensor design. Many suppliers of touch technology offer dedicated black-box, ASIC-style touch controllers that match up with specific touch sensors. They work for their dedicated application, but the customer has limited design flexibility. These fixed solutions do not allow for code modifications, if a small change is introduced during the development or production cycle. For example, if a designer wants to make a simple sensor design change in size or construction, this type of change could be considered a redesign and would require extensive work with the touch-sensor supplier to update their code and sensor design.

Also, these closed solutions do not allow customers to integrate code for other functions, such as LED control, WiFi or IR into the same controller to create a multi-functional device with touch. Customers can miss opportunities for cost reduction and efficiency by being locked into a closed solution. It is also difficult for customers to manage their development cycles and to deploy next-generation designs for cost reduction and feature enhancement.

Customers should not be boxed in by hardware and software in their PCAP solution. One approach to meet the challenge of providing flexible design changes and efficiencies is to empower designers with source-code access and tools that enable them to independently make further customisation and create optimised solutions for their applications. This design flexibility allows customers to manage their touch-interface solutions to enable fast and targeted modifications on their own timetables without depending on external vendors.

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