AT42QT1010
Figure 3-1. Fast Mode Bursts (SYNC Held High)
SNSK
~1ms
SYNC
3.1.3
Low Power Mode
The QT1010 runs in Low Power (LP) mode if the SYNC pin is held low. In this mode it sleeps for
approximately 80 ms at the end of each burst, saving power but slowing response. On detecting
a possible key touch, it temporarily switches to Fast mode until either the key touch is confirmed
or found to be spurious (via the detect integration process). It then returns to LP mode after the
key touch is resolved, as shown in Figure 3-2 on page 5.
Figure 3-2. Low Power Mode (SYNC Held Low)
Fast detect
integrator
~80 ms
Sleep
Sleep
Sleep
SNSK
SYNC
OUT
3.1.4
SYNC Mode
It is possible to synchronize the device to an external clock source by placing an appropriate
waveform on the SYNC pin. SYNC mode can synchronize multiple QT1010 devices to each
other to prevent cross-interference, or it can be used to enhance noise immunity from low
frequency sources such as 50Hz or 60Hz mains signals.
The SYNC pin is sampled at the end of each burst. If the device is in Fast mode and the SYNC
pin is sampled high, then the device continues to operate in Fast mode (Figure 3-1 on page 5). If
SYNC is sampled low, then the device goes to sleep. From then on, it will operate in SYNC
mode (Figure 3-2). Therefore, to guarantee entry into SYNC mode the low period of the SYNC
signal should be longer than the burst length (Figure 3-3 on page 6).
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9541G–AT42–03/10
ATMEL [ ATMEL ]
