Datasheet

10
AT42QT1040 [DATASHEET]
9524D–AT42–05/2013
Figure 4-1. ~500 ns Pulse On OUT2 Pin
4.3 Speed Selection
Speed selection is determined by a 1 M resistor (RFS resistor) connected between SNSK1 and either Vdd (Fast
Mode) or Vss (Slow Mode).
In Fast Mode, the device sleeps for 16 ms between burst acquisitions. In Slow Mode, the device sleeps for 64 ms
between acquisitions. Hence, Slow Mode conserves more power but results in slightly less responsiveness.
Note: The RFS resistor should always be connected to either Vdd or Vss and not changed during operation of the
device. Changing the RFS option will affect the sensitivity of the particular key. Always check that the
sensitivity is suitable after a change. Retune Cs1 if necessary.
4.4 Moisture Tolerance
The presence of water (condensation, sweat, spilt water, and so on) on a sensor can alter the signal values
measured and thereby affect the performance of any capacitive device. The moisture tolerance of QTouch devices
can be improved by designing the hardware and fine-tuning the firmware following the recommendations in the
application note Atmel AVR3002: Moisture Tolerant QTouch Design (www.atmel.com/Images/doc42017.pdf).
Pulse on OUT2
SNS0K
OUT2
SNS0K
OUT2
~20 ms
Power-on/
Reset
Table 4-2. RFS Resistor
RFS Connected To Mode
Vdd Fast mode
Vss Slow mode