Multi-touch technology application

Over the years, the core control chip of multi-touch technology has evolved from 8-bit to 32-bit and from multi-chip control to single-chip control, with rapid performance improvement. In addition, there is no shortage of innovative touch technologies that have come onto the scene.

1 Large-screen applications: Market demand drives the evolution of capacitive touch technology

Capacitive multi-touch technology has officially entered the consumer electronics field for more than three years and has received a lot of market feedback.

Users believe that the problems that need to be solved by multi-touch technology include the identification and avoidance of misoperations, more accurate positioning, support for pen and finger touch, higher resistance to environmental interference, etc. Manufacturers have optimized the performance of their respective next-generation capacitive touch products based on the above requirements, and further launched single-chip products with lower cost, lower power consumption, stronger performance, and support for large-screen displays, such as Atmel's recently launched maXTouch E series that can support up to 12-inch screens and Cypress's CY8CTMA884 series that can support up to 11.6-inch screens.

Patrick Hanley, Atmel's touch technology marketing manager, said that the maXTouch E series products have enhanced and expanded their functions and performance in response to market needs, mainly in six aspects. First, in terms of noise avoidance and noise suppression, the new series of products have higher frequency agility and more complete noise filtering capabilities; second, it supports multi-touch and stylus operations. The maXTouch E can accurately locate very light touches, including passive conductive styluses that are only 2mm thick; third, the form factor is thinner. The new product can support configurations such as unshielded sensors, touch-on-lens, and on-cell, so that it can be used to produce thinner and lower-cost touch screens; fourth, the display is brighter and the power consumption is lower. Since the number of touch screen layers can be reduced, the brightness of the display can be increased, and the low-power design can also make the device have a thinner battery; fifth, the selection of display panels and chargers is wider, thanks to the high precision of the new products, which can support lower-cost and noisy displays and chargers; sixth, it has better moisture resistance and can track the operation of wet fingers, so it has good working performance in all environments.

According to reports, there are currently four new products in the maXTouch E series. Among them, the mXT768E is the industry's first single-chip capacitive touch screen controller using a 32-bit AVR architecture for applications in tablet computers up to 12 inches, supporting 768 channels and 16 touch points. The product has a fast response speed, a report rate of up to 150Hz, and a significant reduction in power consumption; the mXT224E uses an 8-bit architecture and supports 10-point touch for mobile phones and mobile device applications. Compared with the previous generation of products, the chip performance has also been greatly enhanced. The mXT540E and mXT384E are single-chip products with a 32-bit AVR architecture with new node density and high cost performance, supporting 16-point touch.

Also aimed at large-screen applications, Cypress's new CY8CTMA884 series has 60 sensing I/O channels. Other optimized features include support for 10-finger touch, low power consumption, elimination of hold and palm misoperation, high accuracy and fast scanning, etc.

2 Small and medium screen applications: Touch technology innovation layout future market

Currently, there are only a few solutions that can support large-screen capacitive multi-touch in the world, but there are many touch solutions for mobile devices such as mobile phones. Based on various factors such as cost, both resistive touch and capacitive touch technologies are well used in this market, and the product solutions are relatively mature. In order to plan for the future as early as possible, some innovative technical products have begun to appear in the field of small and medium-sized screen touch, such as the single-layer multi-touch solution recently launched by IDT, a company specializing in analog and digital technologies.

According to Eric Itakura, strategic marketing director of IDT's Advanced User Interface Division, IDT's latest technology solution can achieve true single-layer multi-point capacitive touch. "The standard or traditional method is to use a general-purpose controller plus a multi-layer indium tin oxide conductive film (ITO) array using a standard matrix to form a consistent multi-touch solution; IDT's latest method is to use a proprietary single-layer, multi-touch sensor combined with a high noise-resistant controller IC to form an optimized low-cost solution." Itakura said.

Typically, a standard capacitive touch screen sensor requires three conductive layers, including an X sensor, a Y sensor, and a shielding layer. The price of a 5-inch ITO layer is about $1 per layer.

It is reported that the single-layer touch screen design can be realized through IDT's patented sensor technology, which saves about $2 by eliminating the two ITO layers in the traditional touch screen. At the same time, the light transmittance and yield rate are improved. Itakura pointed out that compared with traditional touch screen technology, IDT's single-layer technology does not use the previous sensor cross-arrangement matrix, so multi-touch ghosting is eliminated. In addition, the technology can also support the use of ITO alternative materials such as carbon nanotubes to achieve continuous roll-to-roll ITO production and manufacturing, thereby further reducing production costs. "Our capacitive touch solution has achieved innovations in both sensors and controllers. The innovation of the sensor lies in the realization of a true single-layer multi-touch design, the elimination of multi-point ghosting, and a unified X/Y resolution; the innovation of the controller lies in advanced multi-touch algorithms, high noise immunity, and no need for a shielding layer." He said.

Currently, IDT has launched two chips, LDS7000 and LDS7001, for single-layer multi-touch, which support 30 channels and 35 channels respectively, and the maximum applicable screen size is 3.5 inches and 5 inches respectively. This series of chips is mainly used in small-size screen applications such as mobile phones, and supports IDT single-layer sensor touch screens. "In addition to high noise resistance and no need for a shielding layer, the advantages of LDS7000 and LDS7001 also have an 8ms data rate, which supports a very sensitive touch experience. Other features include 10-bit X/Y resolution, which can reduce the resolution to match the display; and a 32-bit processor core, which can achieve customized additional processing power and storage space expansion, including support for integrated gesture functions," said Itakura.

3 Conclusion

Looking ahead, mobile phones will remain the main battlefield for touch technology in the near future. However, the demand for touch control on large screens such as tablet computers will enter a period of rapid growth starting from 2011. With the further development of technology, new interactive methods such as force feedback and gesture input will also become one of the focuses of touch technology research.