AT42QT1111-MU Atmel, AT42QT1111-MU Datasheet - Page 37

• Manufacturer Part Number: AT42QT1111-MU
• Description: IC TOUCH SENSOR 11KEY QFN
• Manufacturer: Atmel
• Series: QTouch™r
• Type: Capacitiver

Specifications of AT42QT1111-MU

• Touch Panel Interface: 10, 2-Wire
• Number Of Inputs/keys: 11 Key
• Data Interface: Serial, SPI™
• Voltage Reference: Internal
• Voltage - Supply: 3 V ~ 5.5 V
• Current - Supply: 12mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN Exposed Pad
• Output Type: Logic
• Interface: SPI
• Input Type: Logic
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: AT42QT1111-MU; AT42QT1111-MUTR

7.17
9571A–AT42–02/10
Addresses 31–41: Negative Drift Compensation (NDRIFT)/Negative Recalibration Delay (NRD)
Table 7-17.
KEY_n_NDRIFT: the negative drift compensation for key n (where n is 0–10).
When changing ambient conditions cause a change in the key signal, the QT1111 will
compensate through its drift functions. “Negative Drift” refers to the case where the signal for a
key is lower than the reference. Drift compensation occurs at a rate of 1 count per drift
compensation period. The entered number is a multiple of 320 ms.
Note that as a key touch, or an approaching touch, naturally causes a negative change in the
signal, negative drift should be carried out at a much slower rate than positive drift. Otherwise, a
slowly approaching finger will not cause a touch detection, as the falling signal could be
compensated through the negative drift mechanism.
Note:
KEY_n_NRD: the negative recalibration delay for key n (where n is 0–10).
In order to avoid a situation where a key remains “stuck” in detect due to, for example, changing
environmental conditions, the “Negative Recalibration Delay” sets an upper limit on how long a
key can remain “touched”. When this time is exceeded, the QT1111 (that is, all keys) is
recalibrated, taking this key (and any others which are in detect) out of detection. This delay is
set in a multiple of 2560 ms.
Note:
Default KEY_n_NDRIFT value:
Default KEY_n_NRD value:
Address
31
32
33
34
35
36
37
38
39
40
41
Drift compensation timing is paused while Drift Hold is activated, and continues when
Drift Hold has timed out.
A setting of “0” disables the NRD Timeout.
Bit 7
Negative Drift Compensation/Negative Recalibration Delay
Bit 6
KEY_10_NDRIFT
KEY_0_NDRIFT
KEY_1_NDRIFT
KEY_2_NDRIFT
KEY_3_NDRIFT
KEY_4_NDRIFT
KEY_5_NDRIFT
KEY_6_NDRIFT
KEY_7_NDRIFT
KEY_8_NDRIFT
KEY_9_NDRIFT
AT42QT1111-MU/AT42QT1111-AU
Bit 5
7 (2240 ms)
10 (25.6 seconds)
Bit 4
Bit 3
Bit 2
KEY_10_NRD
KEY_0_NRD
KEY_1_NRD
KEY_2_NRD
KEY_3_NRD
KEY_4_NRD
KEY_5_NRD
KEY_6_NRD
KEY_7_NRD
KEY_8_NRD
KEY_9_NRD
Bit 1
Bit 0
37