at42qt1481 ATMEL Corporation, at42qt1481 Datasheet - Page 6

• Manufacturer Part Number: at42qt1481
• Description: 48-key Qmatrix Ic
• Manufacturer: ATMEL Corporation

2. Hardware and Functional
2.1
6
Introduction
AT42QT1481
The AT42QT1481 (QT1481) is a digital burst mode sensor, designed specifically for matrix
layout touch controls; it includes all signal processing functions necessary to provide stable
sensing under a wide variety of changing conditions. Only a few external parts are required for
operation. The entire circuit can be built within a few square centimeters of single-sided PCB
area. CEM-1 and FR1 punched, single-sided materials can be used for the lowest possible cost.
The PCB’s rear can be mounted flush on the back of a glass or plastic panel using a
conventional adhesive, such as 3M VHB two-sided adhesive acrylic film.
The QT1481 employs transverse charge-transfer (QT
changes in electrical charge forced across two electrode elements by a pulse edge (see
Figure
Figure 2-1.
The QT1481 allows a wide range of key sizes and shapes to be mixed together in a single touch
panel. The QT1481 is designed for use with up to 48 keys.
The QT1481 uses both UART and SPI interfaces (only one at a time) to allow key data to be
extracted and to permit individual key parameter setup. The interface protocol uses simple
single byte commands and responds with single byte responses in most cases. The command
structure is designed to minimize the amount of data traffic while maximizing the amount of
information conveyed.
In addition to normal operating and setup functions the QT1481 can also report back actual
signal strengths and error codes.
QmBtn
back key status and signal levels in real time.
A Debug output interface is also supported, which can be used to monitor many operating
variables during product development.
The QT1481 incorporates many tests and checks to enable a product to achieve FMEA and
EN60730 compliance. The results of some tests need to be checked by the host. To achieve a
compliant design, the host must read back the test results and confirm their validity.
The QT1481 is able to scan the touch matrix twice as fast as previous generation devices; it can
take twice the number of samples in a given time frame. This means the QT1481 is much better
equipped to continue normal operation in the face of heavy noise.
2-1).
™
software for the PC can be used to program the operation of the IC as well as read
Field Flow Between X and Y Elements
element
X
™
) sensing, a technology that senses
overlying panel
elem ent
Y
9621B–AT42–06/11