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PDF AT42QT1085 Data sheet ( Hoja de datos )
| Número de pieza | AT42QT1085 | |
| Descripción | QTouch 8-key Touch Sensor IC | |
| Fabricantes | ATMEL Corporation | |
| Logotipo |  |
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Features
• QTouch® Sensor Channels
– Up to 8 keys
• Integrated Haptic Engine
– Haptic events may be triggered by touch detection or controlled by a host
microcontroller over SPI
• Data Acquisition
– QTouchADC key measurement/touch detection method
– Configurable measurement timing and averaging
– Spread spectrum charge transfer
– Raw data from channel measurement can be read over the SPI interface
• GPIO Pins
– 12 dedicated bi-directional GPIO pins, plus up to 4 additional pins (replacing keys)
– Configurable as software PWM Drive, digital inputs or outputs
• Device setup
– Device configuration may be stored in NVRAM
• Operation
– Power-On reset and brown-out detection
– Internal calibrated oscillator
• Key Outline Sizes
– 6 mm x 6 mm or larger (panel thickness dependent); widely different sizes and
shapes possible, including solid or ring shapes
• Key Spacing
– 7 mm centre to centre or more (panel thickness dependent)
• Layers required
– One
• Electrode Materials:
– Etched copper, silver, carbon, ITO
• Electrode Substrates:
– PCB materials; polyamide FPCB; PET films, glass
• Panel materials:
– Plastic, glass, composites, painted surfaces (low particle density metallic paints
possible)
• Panel Thickness:
– Up to 10 mm glass, 5 mm plastic (electrode size dependent)
• Key Sensitivity:
– Individually configured over SPI interface
• Signal Processing:
– Self-calibration, auto drift compensation, noise filtering
– Patented Adjacent Key Suppression® (AKS®) technology to ensure accurate key
detection
• Interface:
– Master/Slave SPI interface, up to 750 kHz
– Object-based communications protocol
• Power:
– 2.0V to 5.5V
• Packages:
– 32-pin 5 x 5 mm MLF RoHS compliant
– 32-pin 7 x 7mm TQFP RoHS compliant
QTouch 8-key
Touch Sensor IC
AT42QT1085
9625C–AT42–12/11
1 page  
AT42QT1085
2. Overview
2.1 Introduction
The AT42QT1085 (QT1085) is an easy to use QTouchADC mode sensor IC based on Atmel
principles for robust operation and ease of design. It is intended for any touch-key application.
There are four dedicated channels configured as keys (Key 0 – Key 3). Another four channels
can be configured as keys or GPIO channels (Key 4 – Key 7 or GPIO 12 – GPIO 15).
There are 12 dedicated GPIO channels (GPIO_0 – GPIO_11).
The QT1085 is capable of detecting proximity or touch on the channels configured as keys.
The keys can be constructed in different shapes and sizes. Refer to the Touch Sensors
Design Guide and Application Note QTAN0079, Buttons, Sliders and Wheels Sensor Design
Guide, for more information on construction and design methods (both downloadable from the
Atmel® website).
Each GPIO channel may be configured as a digital input or output. In output mode, a GPIO pin
may be set to output a PWM signal at any of 16 duty cycles (4-bit PWM). The QT1085 allows
electrodes to project sense fields through any dielectric such as glass or plastic.
This device has many advanced features which provide for reliable, trouble-free operation
over the life of the product. In particular the QT1085 features advanced self-calibration, drift
compensation, and fast thermal tracking. The QT1085 can tolerate some fluctuations in the
power supply, and in many applications will not require a dedicated voltage regulator.
A full haptics engine is integrated into the device, allowing feedback effects to be triggered on
key detection or directly activated by a host microcontroller.
The QT1085 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 and no external Cs capacitors are required.
The QT1085 modulates its acquisition pulses in a spread-spectrum fashion in order to heavily
suppress the effects of external noise, and to suppress RF emissions. This provides greater
noise immunity and eliminates the need for external sampling capacitors, allowing touch
sensing using a single pin.
2.2 Understanding Unfamiliar Concepts
If some of the concepts mentioned in this datasheet are unfamiliar, see the following sections
for more information:
• Section 5 “SPI Protocol for Object Protocol Memory Map Access” on page 14.
9625C–AT42–12/11
5
5 Page 
AT42QT1085
– The user issues a recalibrate command.
A status message is generated on the start and completion of a calibration.
Note that the device performs a global calibration; that is, all the channels are calibrated
together for power-on or user-requested calibration. Only the individual channel is calibrated
for an ATCHCALTHR recalibration.
4.3 Communications
4.3.1
Introduction
The QT1085 communicates as a slave device over a full-duplex 4-wire (MISO, MOSI, SCK,
SS) SPI interface. In addition there is a CHANGE pin which is asserted when a message is
waiting to be read:
• Low = Message waiting
• High = No Message waiting
See Section 7.3 on page 19 for details of the SPI Configuration and Timing Parameters.
Figure 7-1 and Figure 7-2 on page 20 show the basic timing for SPI operation. The host does
the clocking and controls the timing of the transfers from the QT1085.
After the host asserts SS low, it should wait >22 µs in low-power mode before starting SCK; in
Free run mode, a delay of 2 µs is sufficient. The QT1085 reads the MOSI pin with each rising
edge of SCK, and shifts data out on the MISO pin on falling edges. The host should do the
same to ensure proper operation.
SS must be held low for the duration of a communications exchange (a 'Read' or 'Write'
operation). To begin a new communications exchange, SS must be pulled high for at least
2 ms after a Read or 10 ms after a Write and then pulled low. SS should be held high when not
communicating; if SS is low this is taken as an indication of impending communications.
In this case, extra current is drawn, as the QT1085 does not enter its lowest power Sleep
mode.
All timings not mentioned above should be as in Figure 7-2 on page 20.
4.3.2
CHANGE Pin
The QT1085 has an open-drain CHANGE pin which notifies the host when a message is
waiting to be read.
CHANGE is released after each message has been read through an SPI transfer. If further
messages are pending, the QT1085 loads the next one into the Message Handler and then
reasserts (pulls low) the CHANGE pin.
4.4 Signal Processing
4.4.1
Power-up Self-calibration
On power-up, or after reset, all channels are typically calibrated and operational within
200 ms.
9625C–AT42–12/11
11
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| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet AT42QT1085.PDF ] | |
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