Innovation award for multi-function touchscreen controller IC

The Society for Information Display, which runs the Display Week exhibition in San Jose, California named TouchNetix a ‘2019 Best Prototype Honoree’ in its I-Zone awards for innovative display technology. The award was for ‘commercialisation of a multi-function IC that includes capacitive touch, force sensing, and haptic feedback’.

The award follows TouchNetix’ launch of the AX112, the first chip in its aXiom series of touchscreen controller ICs. The aXiom series devices integrate touchscreen control, force-sensing control, proximity sensing and haptic feedback control in a single chip. The product is an all-new design drawing on innovations in controller architecture and in the silicon implementation of the design.

Chris Ard, Managing Director of TouchNetix, said: ‘Before TouchNetix began work on the aXiom series, the market for touchscreen controllers had been starved of development effort – the controllers designed for use in phones and tablets are just good enough to operate adequately behind very thin, flat cover glass. 

“Our goal was to disrupt the market by creating a very high-performance product at a price that is affordable for manufacturers of automotive and industrial equipment. This award from the Society for Information Display is evidence that we have succeeded.’

While competing consumer-grade touchscreen controllers typically feature a signal-to-noise ratio of 50-55dB, the aXiom series devices achieve a high SNR of 80dB. The aXiom chips’ high SNR results in robust touch-sensing performance in noisy industrial and automotive environments, as well as reliable detection of touches when the screen is wet or used with gloves. 

It also supports innovative touchscreen designs incorporating ridges and bumps to guide the user’s hand by touch, enabling the finger’s capacitance to be detected even through an acrylic overlay thicker than ten millimetre. 

By integrating touch, proximity, hover, force sensing and haptic feedback control into a single chip, TouchNetix enables manufacturers of industrial, medical and automotive display systems to simplify their designs, minimise latency, and co-ordinate touch, force and haptic events while imposing almost no burden on the system host processor. 

The aXiom products owe their performance to a combination of a novel analogue front end which uses a narrowband, low-voltage sinusoidal drive waveform, frequency diversity to avoid electrical noise, and a high-performance proprietary digital signal processor (DSP) engine. A key feature of this new architecture is its high signal-to-noise ratio (SNR) of 80dB, compared to the typical 50-55dB of competing products in the market.

This high SNR is enabled with TouchNetix’ aXiom controller while driving the sensor at a low DC-neutral 2.5Vpk-pk, whereas other controllers often use a drive voltage of +30V or higher to achieve even a modest SNR. The aXiom IC’s low drive voltage produces very low levels of radiated emissions. The DC neutral bias also dramatically reduces the stresses experienced by the touchscreen materials. High drive voltages can result in optical damage and even metal migration - a form of galvanic corrosion – in the sensor material leading to premature failure of the touchscreen sensor stack. 

The chip’s powerful DSP engine enables micro-adjustment of the sensitivity at each node in the sensor matrix: the screen’s touch-sensing behaviour can be tuned regionally to provide uniform responsiveness to touch across a screen with an overlay of variable thickness. This allows OEMs to rethink the display user interface (UI), building in contours, ridges or valleys to guide the user’s finger while the user looks away from the screen. 

The aXiom controller can also perform capacitive proximity sensing at a distance of up to ten centimetres, and coarse position sensing of a finger as much as six centimetres distant from the screen, supporting new functions in touchscreen UIs such as zoom-on-approach or hidden-until-lit display concepts. 

In addition, the controller integrates concurrent force sensing and haptics control, to allow the touchscreen to guide the user’s finger through space to their chosen button, touch it, and only register a button press when force is detected at the button’s location. The device’s high-performance force-sensing measurement engine detects displacement of 5µm or less. 

The aXiom controller ICs support touchscreens with up to 56x56 sensing channels, and touch- and force-sensing sampling rates of more than 200Hz. They are suitable for use with displays bigger than 15.6” diagonal, with non-standard form factors and arbitrary aspect ratios.