Atmel Targets Mobile Devices with Capacitive Touch Button Controller
Atmel has announced a low cost touch sensor IC, which brings capacitive user interfaces to price-sensitive consumer and mobile devices. This AT42QT1040 device is available in a 3mm x 3mm VQFN 20 pin package, making it ideal for use in mobile phones and other handheld devices where PCB space is at a premium. In low power mode the AT42QT1040 draws only 31uA from a 1.8 VDC supply, allowing capacitive sensing to be added with minimal impact on battery lifetime.
The AT42QT1040 is the latest solution from Atmel’s touch sensor division, which develops capacitive touch button, slider, wheel and touchscreen controllers. The AT42QT1040 includes 4 digital output channels, enabling per-channel indication on touch detection. The IC can also 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.
The AT42QT1040 is based on Atmel’s patented QTouch charge-transfer sensing method. This robust technology uses spread-spectrum modulation to achieve high immunity to electrical noise. Atmel’s patented Adjacent Key Suppression (AKS), technology, essential for tight-pitched keys, is used to ensure that only the intended key is activated by the touch of a finger. Long-term reliability is achieved because the device automatically calibrates on power-up and always 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.
Individual key sensitivity can be configured to support a range of front panel thicknesses and materials including glass or plastic up to several millimeters thick. Electrodes can be made from copper, silver, carbon, indium tin oxide (ITO) or any other conductive material. Widely different electrode sizes and shapes are possible, giving the product designer great flexibility to tailor the user interface. The device has two power modes: a low power mode, which is ideal for small, battery-driven devices and a fast response mode, which provides minimum response time for applications where low touch latency is essential. To aid product development the AT42QT1040 has a debug mode in which internal data from the chip can be accessed. The ability to monitor the behavior of the device in this way means that designs can quickly be evaluated and tuned resulting in a shorter product design time frame.