New industrial grade touchscreen

Louise Smyth

TouchNetix has announced the introduction of the first in its aXiom series of touchscreen controller ICs.

They have been designed from the ground up for operation in harsh and noisy industrial and automotive environments and over a wide temperature range. The all-new, highly digital architecture gives it performance advantages that are impossible for modified consumer-grade touchscreen controllers to match.

The aXiom products owe their performance to a combination of a novel analogue front end which uses a narrowband, low-voltage sinusoidal drive waveform, an innovative seamless frequency-changing capability to avoid noisy frequency ranges, and a high performance proprietary digital signal processor (DSP) engine. The most striking 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 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 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 aXiom IC's high SNR also enables reliable multi-point touch sensing through thick overlays, including acrylic thicker than 10mm or with an air gap in the stack, and even when the user wears gloves. Touch response to wet fingers, or when the screen is wet, is also superior to that of existing touchscreen controllers.

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 10 cm, and coarse position sensing of a finger as much as 6 cm distant from the screen. This supports new hover and proximity functions in touchscreen UIs. In addition, the AX310 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 AX310's high-performance force-sensing measurement engine detects displacement of as little as 5µm. 

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