Capacitive touch sensing IP enables HMI applications

16th July 2014

Renesas

Nat Bowers

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Suitable for home appliances and healthcare equipment, such as blood pressure and blood glucose meters, Renesas has announced the development of intellectual property (IP) that implements industry-leading capacitive touch sensing technology. The company will also be providing development tools to ease application development.

Compared to Renesas’ R8C/3xT microcontrollers, the IP achieves five times greater high-touch sensitivity. With high- noise immunity allowing the technology to pass strict noise tests, the IP supports the mutual capacitance method which is more reliable and versatile than the common self-capacitance method.

Touch-key interfaces are increasingly being adopted for human machine interface (HMI) applications for electric and electronic equipment because it can easily improve reliability in product design, and enhance the end-user experience. System manufacturers are even starting to develop touch interfaces with a curved surface, instead of the currently mainstream flat panels.

For home kitchen appliances, more robustness is required since the appliance may be splashed with water or the user may be wearing gloves. Strong electromagnetic fields may also be exhibited by equipment such as IH (Induction Heating) stoves. Therefore a technology providing high sensitivity and high noise immunity is necessary to reliably respond to the static capacitance when such end products are operated by the user's hand.

As the IP passes the strict electromagnetic noise testing stipulated in the International Electrotechnical Commission (IEC) 61000-4-3 and IEC 61000-4-6 standards, it enables the design of robust systems even under noisy conditions. Ensuring that false detections do not occur even if there is water on the touch key area, the IP supports the mutual capacitance method which makes it easier to implement moisture proofing measures in end products.

The high-level of touch sensitivity enables the IP to be used with gloved hands and for proximity sensing, where there is no actual touch. The IP also supports embedding touch keys in a matrix configuration to eliminate false ghost detections, a phenomenon associated with devices implementing the self-capacitance method. This allows the number of touch keys to be increased with minimal number of pins.

Renesas plans to provide a new development environment that maintains compatibility with the existing Renesas tool chain while improving ease of use for its customers.

Samples of the Renesas MCUs incorporating the new static capacitive touch panel IP will be available during the fiscal year 2014.