Atmel has introduced a four channel capacitive touch switch controller for battery products from its Hampshire-based design centre.

The IC can be configured using one channel as a proximity sensor, enabling hidden-until-lit user interfaces where the device detects the presence of a finger some distance away from the keypad.

Charge-transfer sensing, originally patented by Quantum Research - which Atmel bought last year - uses spread-spectrum modulation to improve immunity from electrical noise.

Adjacent key suppression is provided for tight-pitched keys.

The AT42QT1040 is available in a 3x3mm 20pin VQFN package and in low-power mode it draws 31µA from a 1.8V supply.

It calibrates on power-up and “stays calibrated even if there is a build-up of moisture or other contaminants on the touch surface or if the overall system is subject to aging”, claimed the firm. “Individual key sensitivity can be configured to support a range of front panel thicknesses and materials including glass or plastic up to several millimetres thick.”

Electrodes can be made from any conductive material including metals, ITO and carbon, and a wide range of electrode sizes and shapes can be accommodated.

Fast response mode cuts detection latency at the expense of power consumption, and there is a debug mode where internal data from the chip can be accessed.

More information: www.atmel.com