AT42QT1011 View Datasheet(PDF) - Atmel Corporation

Part Name

Description

Manufacturer

AT42QT1011

Single-key QTouch® Touch Sensor IC

Atmel Corporation 

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 QT1011 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 7). 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).

Figure 3-3. SYNC Mode (Triggered by SYNC Edges)

SNSK

sleep sleep

sleep

Revert to Fast Mode

SYNC

slow mode sleep period

SNSK

SYNC

sleep sleep

sleep

slow mode sleep period

Revert to Slow Mode

However, once SYNC mode has been entered, if the SYNC signal consists of a series of short pulses (>10 µs) then

a burst will only occur on the falling edge of each pulse (Figure 3-4) instead of on each change of SYNC signal, as

normal (Figure 3-3).

In SYNC mode, the device will sleep after each measurement burst (just as in LP mode) but will be awakened by a

change in the SYNC signal in either direction, resulting in a new measurement burst. If SYNC remains unchanged

for a period longer than the LP mode sleep period (about 80 ms), the device will resume operation in either Fast or

LP mode depending on the level of the SYNC pin (Figure 3-3).

There is no detect integrator (DI) in SYNC mode (each touch is a detection); see Section 3.4 on page 9.

Recalibration timeout is a fixed number of measurements so will vary with the SYNC period.

Figure 3-4. SYNC Mode (Short Pulses)

SNSK

SYNC

>10 μs

>10 μs

>10 μs

AT42QT1010 [DATASHEET]

8

9542I–AT42–05/2013

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