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AT42QT2100 [DATASHEET]

9554E–AT42–01/13

3.8

PCB Cleanliness

Modern no-clean-flux is generally compatible with capacitive sensing circuits.

3.9

Spread-spectrum Circuit

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:

If a PCB is reworked to correct soldering faults relating to the QT2100, or 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.