6

9542G–AT42–03/10

AT42QT1011

Figure 3-3.

SYNC Mode (Triggered by SYNC Edges)

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 on

page 6) 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.

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

Figure 3-4.

SYNC Mode (Short Pulses)

3.2

Threshold

The internal signal threshold level is fixed at 10 counts of change with respect to the internal

reference level, which in turn adjusts itself slowly in accordance with the drift compensation

mechanism.

The QT1011 employs a hysteresis dropout of two counts of the delta between the reference and

threshold levels.

3.3

Max On-duration

The max on-duration of this device is infinite; that is, the device will not automatically recalibrate

due to a persistant detection.

SYNC

SYNC

SNSK

SNSK

slow mode sleep period

sleep

sleep

sleep

sleep

sleep

sleep

Revert to Fast Mode

Revert to Slow Mode

slow mode sleep period

SNSK

SYNC

>10us

>10us

>10us