Touch controller highlights reliability, trims component count

Atmel Corp.'s AT42QT1060 is a touch control chip that integrates 6 channels of touch sensing with the ability to drive up to 7 low current LEDs directly through a pulse width modulated (PWM) output function. The device operates from 5.5Vdc down to 1.8Vdc and consumes less than 1?A in standby mode to give long battery life; it comes in a tiny 4mm x 4mm MLF28 package, making it ideal for use in mobile phones and other handheld devices. The AT42QT1060 is the latest addition to Atmel's range of capacitive touch controllers based on Quantum Research Group's charge-transfer technology. These include QTouch and QMatrix based controllers for single and multiple touch buttons, touch sliders and touch wheels.

The AT42QT1060 is designed for use in portable electronics products. An inbuilt capacitive guard channel feature helps prevent false triggering, for example, where moisture is an issue. This feature also prevents against erroneous commands that can occur when devices such as MP3 players are carried in a pocket, or in the case of a cellular phone, when it is held against the ear. The highly integrated AT42QT1060 reduces component count, cutting design complexity and cost, and enabling faster product development.

The sensor chip is based on Quantum's patented QTouch charge-transfer sensing method. This robust technology uses spread-spectrum modulation to achieve high immunity to electrical noise and a patented technique—Adjacent Key Suppression (AKS)—ensures that only the intended key is activated by the touch of a finger. The guard channel feature uses AKSTM to eliminate false triggering of nearby keys. Long-term reliability is ensured because the device automatically re-calibrates on power-up, compensating for build-up of moisture or other contaminants on the touch surface. Individual key sensitivity is host-selectable.

A host wake up function allows the host to sleep and be woken up when a user triggers the corresponding input, providing another power-saving feature. Additional GPIO expansion can be achieved by the use of spare IC pins.

The AT42QT1060 functions through any insulating panel including glass or plastic up to 3mm thick. Electrodes can be made from copper, silver, carbon, indium tin oxide or Orgacon conductive ink and must be 6mm x 6mm or larger. Widely different electrode sizes and shapes are possible, giving the product designer great flexibility in tailoring the user interface.

Samples of the AT42QT1060 are available now in a space-saving 4mm x 4mm package. The device is priced at $0.89 in quantities of 100,000 units per year. A demonstration board is also available.