AT42QT1011-TSHR View Datasheet(PDF) - Atmel Corporation
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AT42QT1011-TSHR Datasheet PDF : 25 Pages
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The value of Cs also has a dramatic effect on sensitivity, and this can be increased in value with the trade-off of
slower response time and more power. Increasing the electrode's surface area will not substantially increase touch
sensitivity if its diameter is already much larger in surface area than the object being detected. Panel material can
also be changed to one having a higher dielectric constant, which will better help to propagate the field.
In the case of proximity detection, usually the object being detected is on an approaching hand, so a larger surface
area can be effective.
Ground planes around and under the electrode and its SNSK trace will cause high Cx loading and destroy gain. The
possible signal-to-noise ratio benefits of ground area are more than negated by the decreased gain from the circuit,
and so ground areas around electrodes are discouraged. Metal areas near the electrode will reduce the field strength
and increase Cx loading and should be avoided, if possible. Keep ground away from the electrodes and traces.
2.4.3 Decreasing Sensitivity
In some cases the QT1011 may be too sensitive. In this case gain can be easily lowered further by decreasing Cs.
2.4.4
Proximity Sensing
By increasing the sensitivity, the QT1011 can be used as a very effective proximity sensor, allowing the presence of
a nearby object (typically a hand) to be detected.
In this scenario, as the object being sensed is typically a hand, very large electrode sizes can be used, which is
extremely effective in increasing the sensitivity of the detector. In this case, the value of Cs will also need to be
increased to ensure improved sensitivity, as mentioned in Section 2.4.2. Note that, although this affects the
responsiveness of the sensor, it is less of an issue in proximity sensing applications; in such applications it is
necessary to detect simply the presence of a large object, rather than a small, precise touch.
AT42QT1010 [DATASHEET]
6
9542I–AT42–05/2013
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