Single-chip touch control for Windows 8 tablets

April 30, 2013 // By Graham Prophet
Atmel has extended its maxTouch range of touch controller ICs with the T-series. With high volumes of touch products being marketed in smartphone/handset and tablet formats, Atmel has optimised this product for that sector.

The mXT2952T is, according to Rob Frizzell, Director Touch Product Marketing in Atmel, mXT2952T: the first ultra low-power, single chip, capacitive touch solution for Windows 8 certified 15.6-in. displays. This conforms to the Windows 8 specification of up to 15.6 inch – but you can control an larger touch screen under Linux or Android, Frizzell says. The series offers solutions for screens of 3 to 23 inches. The company has incorporated several of the features it has developed for existing Atmel touch products. You can use the maxStylus (on screens of up to 13.3 in.), and active stylus that interacts with the touch sensing matrix without the need for an extra sensor layer; the maxFusion SensorHub integrates motion and sensory controls; and the Xsense technology supports the use of flexible and “edgeless” - or frameless – displays.

The maxTouch T uses dual mutual- and self-capacitance sensing, claimed to give the best performance in terms of power, noise immunity, glove-touch sensitivity, moisture-insensitivity and latency. It handles 2952 nodes, has a refresh rate of over 150 Hz, can track at over 60 inches per second, and track 10 touches at over 100 Hz with full noise avoidance. Latency is under 10 msec. You can use fine-line-metal (FLM) screen technology as well as ITO overlays, and a 32-bit AVR-derived microcontroller filters noise, computes multi-touch points, and eliminates false responses. The mXT2952T replaces a 3-chip set to achieve similar results, occupies a 5 x 10 mm package and could yield a functional outline of 6 mm wide by 80 mm long to fit within a typicla potable product build. Frizzell estimates a cost reduction over the 3-chip solution of around 2x.