ATMXT224-CCU

The mXT224 uses a unique charge-transfer acquisition engine to implement the QMatrix capacitive sensing method patented by . This allows the measurement of up to 224 mutual capacitance nodes in under 1 ms. Coupled with a state-of-the-art XMEGA CPU, the entire touch screen sensing solution can measure, classify and track a single finger touch every 4 ms if required. The acquisition engine uses an optimal measurement approach to ensure almost complete immunity from parasitic capacitance on the receiver inputs (Y lines). The engine includes sufficient dynamic range to cope with touch screen mutual capacitances spanning 0.5 pF to 5 pF, allowing great flexibility for use with proprietary ITO pattern designs. One and two layer ITO sensors are possible using glass or PET substrates. The main AVR XMEGA CPU has, under its control, two powerful, yet low power, micro sequencer coprocessors. These combine to allow the signal acquisition, preprocessing, post processing and housekeeping to be partitioned in an efficient and flexible way. This gives ample scope for sensing algorithms, touch tracking or advanced shape-based filtering. An in-circuit reflash can be performed over the chip’s hardware-driven two-wire interface (I²C-compatible). Overall, the mXT224 represents a step improvement over competing technologies, providing a near optimal mix of low power, small size and low part count, while offering unrivalled true multitouch performance.