at42qt2160 ATMEL Corporation, at42qt2160 Datasheet - Page 29

• Manufacturer Part Number: at42qt2160
• Description: Qslide?, 16-key Qmatrix? Sensor Ic
• Manufacturer: ATMEL Corporation

7.14
7.15
9502A–AT42–07/08
Address 17: Detect Integrator
Address 18: Negative Recal Delay
Table 7-14.
Table 7-15.
However, an obstruction over the sense pad, for which the sensor has already made full
allowance, could suddenly be removed leaving the sensor with an artificially suppressed
reference level and thus become insensitive to touch. In this latter case, the sensor should
compensate for the object's removal by raising the reference level relatively quickly (PDRIFT).
Drift compensation and the detection time-outs work together to provide for robust, adaptive
sensing. The time-outs provide abrupt changes in reference calibration depending on the
duration of the signal 'event'.
If PDRIFT or NDRIFT is set to 0 then the drift compensation in the respective direction is
disabled.
Note: it is recommended that the drift compensation rate be more than four times the LP mode
period. This is to prevent undersampling, which decreases the algorithm's efficiency.
Default NDRIFT: 20 (3.2s/reference level)
Default PDRIFT: 5 (0.8s/reference level)
NDIL is used to provide signal filtering.
To suppress false detections caused by spurious events like electrical noise, the device
incorporates a 'detection integrator' or DI counter mechanism. A per-key counter is incremented
each time the key has exceeded its threshold and stayed there for a number of acquisitions in
succession, without going below the threshold level. When this counter reaches a preset limit
the key is finally declared to be touched.
If on any acquisition the signal is not seen to exceed the threshold level, the counter is cleared
and the process has to start from the beginning.
The QT2160 has a built in minimum of 1 DI counts in addition to the NDIL value. Therefore, if
setting a NDIL value of 3, the actual number of consecutive acquisitions is 4.
Available NDIL values are from 1 to 31.
Default: 3 (4 DI value)
If an object unintentionally contacts a key resulting in a detection for a prolonged interval it is
usually desirable to recalibrate the key in order to restore its function, perhaps after a time delay
of some seconds.
Address
Address
17
18
Detect Integrator
Negative Recal Delay
b7
b7
0
b6
b6
0
b5
b5
0
b4
b4
NRD
b3
b3
NDIL
b2
b2
AT42QT2160
b1
b1
b0
b0
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