OMO ElectronicOMO Electronic
Expand menu
Hello, Sign inMy Account
0 Cart

AT42QT1085-MU

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30
7
AT42QT1085 [DATASHEET]
9625D–AT42–05/2013
2.3.3 Guard Channel
A guard channel may be used to prevent accidental touch detection on other keys which share the same Adjacent
Key Suppression (AKS) group. The guard channel is made more sensitive than the others in the AKS group through
a larger touch electrode area combined with higher gain / lower threshold. The QT1085 remains in Idle mode while a
guard channel is in detect, and Touch Automatic Calibration will not occur for a guard key detection.
2.4 Proximity Effect
Any channel can function as a proximity sensor, based on hand or body proximity to a product. This is achieved by
using a relatively large electrode and tuning the QTouchADC and Threshold configuration options. Refer to
QTAN0087, Proximity Design Guide, for more information.
2.5 SPI Interface
The QT1085 is an SPI slave-mode device, utilizing a four-wire full-duplex SPI interface.
There are four standard SPI signals: SS
, SCK, MOSI and MISO.
The QT1085 also provides a CHANGE
signal to indicate when there is a message waiting to be read. This removes
the need for the host to poll the QT1085 continuously.
Communications are performed through Read and Write operations on the Object Protocol memory map.
2.6 Operating Modes
Cycle times, Free-run and Sleep modes are controlled by the Power Configuration T7 object settings.
2.7 Haptics Engine
The QT1085 can be configured to play a selected haptic effect in response to a touch detection, a state change on a
GPIO pin or on demand by the host microcontroller.
A selection of haptic effects is available on the device from the Haptic Event T31 object. The effects include:
Strong Click
Strong Click 60% strength
Strong Click 30% strength
Sharp Click
Sharp Click 60% strength
Sharp Click 30% strength
Soft Bump
Soft Bump 60% strength
Soft Bump 30% strength
Double Click
Double Click 60% strength
Triple Click
Soft Buzz
Strong Buzz
Effects may be assigned to events, such as a key touch or GPIO state change.
Refer to the QTAN0085 Haptics Design Guide Application Note and the AT42QT1085 Protocol Guide for more
information on this object.
8
AT42QT1085 [DATASHEET]
9625D–AT42–05/2013
3. Wiring and Parts
3.1 Bypass Capacitors
One 100 nF bypass capacitor and one 1 µF bypass capacitor must be used on the Vdd digital supply and a 100 nF
capacitor on AVDD. The 100 nF capacitors should be mounted close to the device, within 10 mm if possible.
3.2 Rs Series Resistors
Series Rs resistors (Rs0 – RS7) are in-line with the electrode connections and are used to limit electrostatic
discharge (ESD) currents and to suppress radio frequency interference (RFI). For most applications the Rs resistors
will be in the range 4.7 k – 33 k each. For maximum noise rejection the value may be up to 100 k.
Although these resistors may be omitted, the device may become susceptible to external noise or RFI. For details of
how to select these resistors refer to Application Note QTAN0002, Secrets of a Successful QTouch Design.
3.3 Power Supply
See Section 7. on page 19 for the power supply range. If this fluctuates slowly with temperature, the device tracks
and compensates for these changes automatically with only minor changes in sensitivity. If the supply voltage drifts
or shifts quickly, the drift compensation mechanism will not be able to keep up, causing sensitivity anomalies or false
detections. In this situation a dedicated voltage regulator should be included in the circuit.
The QT1085 power supply should be locally regulated using a three-terminal device. If the supply is shared with
another electronic system, care should be taken to ensure that the supply is free of digital spikes, sags, and surges,
all of which can cause adverse effects.
3.4 QFN Package Restrictions
The central pad on the underside of the QFN chip should be connected to ground. Do not run any tracks underneath
the body of the chip, only ground. Figure 3-1 on page 8 shows an example of good/bad tracking.
Figure 3-1. Examples of Good and Bad Tracking
Example of GOOD tracking Example of BAD tracking
9
AT42QT1085 [DATASHEET]
9625D–AT42–05/2013
3.5 Oscillator
The device has an internal oscillator. No external oscillator or clock input is required.
3.6 PCB Layout and Construction
Refer to Application Note QTAN0079 – Buttons, Sliders and Wheels Sensor Design Guide and the Touch Sensors
Design Guide (both downloadable from the Atmel website), for more information on construction and design
methods.
The sensing channels used for the individual keys can be implemented as per the Touch Sensors Design Guide.
3.7 PCB Cleanliness
Modern no-clean flux is generally compatible with capacitive sensing circuits.
If a PCB is reworked in any way, clean it thoroughly to remove all traces of the flux residue around the capacitive
sensor components. Dry it thoroughly before any further testing is conducted.
3.8 Spread-spectrum Circuit
The QT1085 spectrally spreads its frequency of operation to heavily reduce susceptibility to external noise sources
and to limit RF emissions.
Bursts operate over a spread of frequencies, so that external fields will have a minimal effect on key operation and
emissions are very weak. Spread-spectrum operation works together with the Detect Integrator (DI) mechanism to
dramatically reduce the probability of false detection due to noise.
Spread spectrum is hardwired in the chip and is automatically enabled.
CAUTION: If a PCB is reworked in any way, it is highly likely that the behavior of the no-clean
flux changes. This can mean that the flux changes from an inert material to one that can
absorb moisture and dramatically affect capacitive measurements due to additional leakage
currents. If so, the circuit can become erratic and exhibit poor environmental stability.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30

AT42QT1085-MU

Mfr. #:
Buy AT42QT1085-MU
Manufacturer:
Microchip Technology / Atmel
Description:
Capacitive Touch Sensors 8 Channel QTouch Haptic Sensor IC
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet