AT42QT1110-MU_14 Datasheet, PDF (32/50 Pages) ATMEL Corporation – 11-key QTouch Touch Sensor IC

PHYST: positive hysteresis. This setting provides a greater degree of control over the implementation of the positive
threshold recalibration. The positive hysteresis operates as a “modifier” for the positive threshold. When a key signal
is detected as being over the positive threshold, the positive threshold is reduced by a factor corresponding to the
positive hysteresis so that the key will not go in and out of positive detection when the signal is on the borderline
between drift-compensation of a positive error or recalibration.
The settings for positive hysteresis are:
00 = No change to positive threshold
01 = 12.5% reduction in positive-detect threshold
10 = 25% reduction in positive-detect threshold
11 = 37.5% reduction in positive-detect threshold
Default PTHR value:
Default PHYST value:
4 (4 counts above reference)
2 (25% positive hysteresis)
7.8 Address 4: Positive Drift Compensation (PDRIFT)
Table 7-6. Positive Drift Compensation
Address
Bit 7
Bit 6
Bit 5
4
0
Bit 4
Bit 3
PDRIFT
Bit 2
Bit 1
Bit 0
When changing ambient conditions cause a change in the key signal, the QT1110 will compensate through its drift
functions. Positive Drift refers to the case where the signal for a key is greater than the reference.
Drift compensation occurs at a rate of 1 count per drift compensation period.
PDRIFT: the drift compensation period, in multiples of 160 ms. The valid range is 0 to 127, where 0 disables positive
drift compensation.
Note: Drift compensation timing is paused while Drift Hold is activated, and continued when Drift Hold has timed
out.
Default value:
6 (960 ms)
7.9 Address 5: Positive Recalibration Delay (PRD)
Table 7-7. Positive Recalibration Delay
Address
Bit 7
Bit 6
Bit 5
5
Bit 4
Bit 3
PRD
Bit 2
Bit 1
Bit 0
If a key signal is determined to be above the positive threshold, the QT1110 will wait for this delay and confirm that
the error condition is still present before initiating a recalibration.
PRD: the positive recalibration delay, in multiples of 160 ms.
Note: All keys are recalibrated in the case of a positive recalibration.
Default value:
6 (960 ms)
AT42QT1110-MU / AT42QT1110-AU [DATASHEET] 32
9520J–AT42–05/2013