at42qt2100 ATMEL Corporation, at42qt2100 Datasheet - Page 10

• Manufacturer Part Number: at42qt2100
• Description: Qtouch Touch Sensor Ic
• Manufacturer: ATMEL Corporation

3.6
3.7
3.8
3.9
10
Oscillator
PCB Layout and Construction
PCB Cleanliness
Spread-spectrum Circuit
AT42QT2100
No external oscillator is needed.
Refer to Application Note QTAN0079, Buttons, Sliders and Wheels Sensor Design Guide and
the Touch Sensors Design Guide (both downloadable from the Atmel
information on construction and design methods.
The sensing channels used for the individual keys can be implemented as per the Touch
Sensors Design Guide.
Modern no-clean-flux is generally compatible with capacitive sensing circuits.
The QT2100 offers the ability to spectrally spread its frequency of operation to heavily reduce
susceptibility to external noise sources and to limit RF emissions.
With this option enabled, bursts operate over a spread of frequencies, so that external fields
will have 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 may be enabled by connecting the SPREAD pin to Vdd via a pull-up resistor,
or disabled by connecting to Vss via a pull-down resistor.
CAUTION:
to any associated traces or components, be sure that you fully understand the nature
of the flux used during the rework process. Leakage currents from hygroscopic ionic
residues can stop capacitive sensors from functioning. If you have any doubts, a
thorough cleaning after rework may be the only safe option.
If a PCB is reworked to correct soldering faults relating to the QT2100, or
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website), for more
9554CX–AT42–11/11