Single-chip simplifies touch sensor design

The Programmable Radio-on-Chip User Interface (PRoC-UI) Product of the Year winner from Cypress Semiconductor was in response to the touch capabilities of operating systems such as Windows 8. When it was introduced, the only way an engineer could design a touch product was to use three different ICs from a couple of vendors. The PRoC-UI is a single chip solution that helps designers because they only have to learn one integrated development environment and don’t have to deal with multiple vendors. The engineer also saves on BOM and board space. Even though Windows 8 prompted this design, the product will likely be adopted in other markets including remotes for Smart TVs, set-up boxes and keyboards for TVs to allow accessing the internet.

The biggest challenge the team faced was integrating two IPs — for RF and touch sensing — because they interfere with each other when placed in a single chip. Both RF and touch sensing are prone to noise from switching signals. Also, the challenge was not limited to routing inside the device. The team also had to figure out how to make it easy for the engineer to lay out a design. The team tried different routing options and simulated and characterized the receive sensitivity on the radio pins and the signal-to-noise ratio on the touch-sensing pins. Even with the best design, they had to disable touch sensing on a couple of I/Os to avoid a drop in receive sensitivity.

The PRoC-UI solution does touch sensing, acts as a general-purpose MCU, and receives and transmits radio packets. The team wanted to make the device powerful enough to do all this and be a low-cost solution and a low-power device, while maintaining a good system refresh rate. They had to make sure that the digital and analog resources used were just enough to support the target applications.

It took a global team of 10 members about 45 weeks to characterize and validate the integrated RF and touch-sensing functions.