User Manual
7
9570H–AT42–02/10
AT42QT1110-MZ/AT42QT1110-AZ
2. Overview of the AT42QT1110
2.1 Introduction
The AT42QT1110 (QT1110) is a digital burst mode charge-transfer (QT
™
) capacitive sensor
driver designed for any touch-key applications.
The keys can be constructed in different shapes and sizes. Refer to the Touch Sensors Design
Guide and Application Note QTAN0002, Secrets of a Successful QTouch™ Design, for more
information on construction and design methods (both downloadable from the Atmel
®
website).
The device includes all signal processing functions necessary to provide stable sensing under a
wide variety of changing conditions, and the outputs are fully debounced. Only a few external
parts are required for operation.
The QT1110 modulates its bursts in a spread-spectrum fashion in order to suppress heavily the
effects of external noise, and to suppress RF emissions.
2.2 Configurations
The QT1110 is designed as a versatile device, capable of various configurations. There are two
basic configurations for the QT1110:
• 11-key QTouch. The device can sense up to 11 keys.
• 7-key QTouch with individual outputs for each key. The device can sense up to 7 keys and
drive the matching Detect outputs to a user-configurable PWM.
Both configurations allow for a choice of acquisition modes, thus providing a variety of
possibilities that will satisfy most applications (see the following sections for more information).
Additionally, the SYNC line can be used as an external trigger input. Note that in 11-key mode
the SYNC line replaces one key, thus allowing only 10 keys.
See Section 4.7 on page 18 for more information.
2.3 Guard Channel
The device has a guard channel option (available in all key modes), which allows one key to be
configured as a guard channel to help prevent false detection. See Section 4.9 on page 19 for
more information.
2.4 Self-test Functions
The QT1110 has two types of self-test functions:
• Internal Hardware tests – check for hardware failures in the device’s internal memory.
• Functional checks – confirm that the device is operating within expected parameters.
See Section 4.10 on page 20 for more information.