Renesas’ IP for capacitive touch sensing improves HMI performance

July 16, 2014 // By Graham Prophet
Renesas Electronics Europe has developed intellectual property (IP) that implements leading-performance capacitive touch sensing technology suitable for home appliances, and healthcare equipment, such as blood pressure and blood glucose meters.

The IP achieves high-touch sensitivity five times better than of Renesas' R8C/3xT microcontrollers (MCUs), as well as high- noise immunity allowing the technology to pass strict noise tests. For the first time, Renesas IP now supports the mutual capacitance method which is more reliable and versatile than the common self-capacitance method. Renesas will also provide development tools to make application development easier.

For human machine interface (HMI) applications for electric and electronic equipment, touch-key interfaces have been the subject of increasing attention. System manufacturers are now developing new touch interfaces with a curved surface, instead of the flat panels that have been mainstream up to now. Looking ahead, touch-sensing technologies with even higher sensitivity and noise immunity will become highly desirable for a wider range of applications.

For home appliances used in the kitchen, it is often the case that the appliance will be splashed with water or the user will be wearing gloves. Furthermore, there is also equipment, such as IH stoves, that emit strong electromagnetic fields. This means that a technology that achieves both high sensitivity and high noise immunity at the same time is required to reliably respond to the static capacitance when such end products are operated by the user's hand.

Renesas launched its R8C/3xT Series of MCUs supporting capacitive touch interfaces in October 2009, in ti s own words, “contributing to the proliferation of touch-key manipulation systems.”

The Renesas IP not only offers high-noise immunity, but also provides characteristics that allow reliable sensing even with acrylic panels with thicknesses in excess of 10 mm. The technology can implement flexible designs, for example products that implement curved panels. Furthermore, since this new IP enables a high-level of touch sensitivity it can expand the range of scenarios for consumer interaction, such as gloved hands and proximity sensing where there is no actual touch. In addition, since the IP passes the strict electromagnetic noise testing stipulated in the