Touchscreen controller also integrates haptics control
The new controller combines 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, together with a high-performance proprietary digital signal processor (DSP) engine. This new architecture has a high signal-to-noise ratio (SNR) of 80dB, compared to the typical 50-55dB of competing products in the market, claims the manufacturer.
The aXiom controller drives the capacitive 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. This in turn produces very low levels of radiated emissions and the DC neutral bias also dramatically reduces the stresses experienced by the touchscreen materials. 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. The chip’s 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 5 µm. The aXiom controller ICs support touchscreens with up to 56×56 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, and in non-standard form factors and arbitrary aspect ratios. TouchHub development software is provided with the aXiom controllers to ease the design and tuning of touchscreen designs.
TouchNetix – www.touchnetix.com