at42qt1481 ATMEL Corporation, at42qt1481 Datasheet - Page 50

• Manufacturer Part Number: at42qt1481
• Description: 48-key Qmatrix Ic
• Manufacturer: ATMEL Corporation

5.21
5.22
50
Awake Time – AWAKE
Drift Hold Time – DHT
AT42QT1481
The AWAKE feature is effective only if the part has been configured for automatic sleep, via
SDC, and if the sleep command (0x16) has been issued. AWAKE determines the period of time
that elapses from the last key release before the part tries to sleep.
An internal timer is restarted at each key release and runs for the time configured via AWAKE.
The part will not enter sleep while this timer is active, or while any of the following conditions are
present:
Note:
This function is programmed on a global basis.
AWAKE default value: 15 (25.4s)
AWAKE range: 0 – 15 (100 ms – 25.4s)
AWAKE Timeout accuracy: to within ±50 ms
Drift Hold Time (DHT) is used to suspend drift compensation from all keys while the keypad is
being used. With the feature enabled, drift compensation is suspended while any key is touched
and also for a period afterwards. DHT defines the length of time the drift compensation
continues to be suspended after a key detection has finished.
This feature is particularly useful in cases of high-density keypads where touching a key or
hovering a finger over the keypad would cause untouched keys to drift, and therefore create a
sensitivity shift, and ultimately inhibit other touch detections.
DHT can be configured to one of 16 values between 100 ms and 25.4s via LUT (see
on page
This function is programmed on a global basis.
DHT default value: 11 (9s)
DHT range: 0 – 15 (100 ms – 25.4s)
• DRDY asserted (low level)
• SS low (assume host trying to send a command)
• A command is being processed or response data is being returned or pending return to the
• Any key calibrating
• Any key touch delta exceeds the threshold (positive or negative)
host
If the sleep feature has been disabled, the QT1481 never sleeps and the AWAKE setup
has no effect. The AWAKE period can be configured to one of 16 values between
100 ms and 25.4s via LUT (see
58).
Table 5-8 on page
58).
9621B–AT42–06/11
Table 5-8