case study # 01

Capacitive Multi-Touch Panel Controller Integrated Circuit

 

Kapik has significant experience in developing mixed-signal controllers for touch-sensitive panels, having worked with two clients that had different very different device parameters.

The first project was for an Asian electronic components manufacturer seeking to enter the touch panel market. This client was seeking an IC and associated detection algorithms for large format multi-touch projected-capacitive touch (PCT) panels (17” or larger, for use in large tablet devices, televisions and computer monitors).

The second project was for a major tier one mobile communications supplier with a high degree of familiarity with touch panel technology. The client required similar technology, however it was intended for small touch panels (5” to 7”), such as those found on small mobile phone and tablets.

Though the physical layouts of the designs needed to vary considerable based on the form factors involved in each client’s project, they shared the following requirements:

  • Effectively handle environmental noise while working within the limits on signal drive strength, such as electromagnetic interference; charger noise; noise injected by the user.
  • Work within power constraints, which included keeping overall power consumption low and managing multiplexing incompatible high and low voltage circuitry.
  • Work with different types of touch panels with different transmit and receive line layouts and which correspondingly respond to touch differently.
  • Manage multiplexing incompatible high and low voltage circuitry to take advantage of the benefits of reversing transmit (TX) and receive (RX) lines on some panel configurations.

With the first client, Kapik was allowed considerable autonomy and decision-making power on design decisions. This enabled us to pioneer an architecture that was highly innovative and helped us address well-known power and noise issues at the time.

Our Walsh-based drive pattern eliminated the need for a specialized high-voltage drive and semiconductor process, which would have added considerable product cost, and improved signal-to-noise ratio (SNR).

We also designed advanced multi-touch algorithms and a firmware that also helped filter out noise and external electromagnetic interference coupled in from the user's body and from the LCD sitting next to the touch panel.

Both our clients were able to benefit from an approach that entailed:

  • Embedding flexibility into all elements of design and development: Both IC architectures had a high degree of flexibility and programmability; a digital architecture that was compatible with a wide range of analog front-end transceiver arrays with minimal power and area overheads. Because the technology was so new, Kapik provided extensive hands-on programming assistance
  • Developing an optimal physical layout: Working iteratively, we were able to ensure that the size of the IC met the required specifications and signal routing didn’t introduce unnecessary noise
  • Analysis and verification: We needed to determine the precise range of signal levels required to optimize SNR; analyze speed and performance requirements to ensure flexibility did not come at the expense of performance; and verify the performance of our schematic analog circuit, core processor and micro-sequencer designs. Finally we conducted testing on a fabricated circuit to ensure accuracy and precision and developed firmware that addressed the testing and verification results

Our second client was able to benefit from the breakthroughs we achieved in our first project as well as important incremental innovations, especially relevant to mobile. We were able to drive power reductions further by enabling circuits to power down when not active; develop a low frequency and power scanning mode that can detect and react to touches via an on-board 8-bit microcontroller; and clock-gate the IC to meet the power requirements for mobile.

In both cases, we achieved first silicon success. Kapik was able to meet the customer service needs and engineering requirements of two very different clients and raise the bar on how touch panel controllers use power, handle noise and respond to touch.

Learn about how we can help you drive engineering innovation into your devices with mixed signal analog. Contact us today.

Tags: customer service, sensor, consumer, power, human-machine, mobile

>