14

AT42QT2100 [DATASHEET]

9554E–AT42–01/13

Figure 4-1.

DRDY Cycle without Communications

Figure 4-2.

DRDY Cycle with Communications

4.3

Signal Processing

4.3.1

Power-up Self-calibration

On power-up, or after reset, all 10 channels are typically calibrated and operational within 350 ms.

4.3.2

Drift Compensation

This operates to correct the reference level of each key automatically over time; it suppresses false detections

caused by changes in temperature, humidity, dirt and other environmental effects.

The QT2100 drifts towards touch at a rate limited to 1 count every 3 seconds, and away from touch at a rate limited

to 1 count every 0.5 s. Reference drift is paused during touch detection, and for 2 s after touch detection ends. These

timings may be slower in Sync mode, or where asynchronous acquisition is triggered with LPB, as timing calculations

are derived from the acquisition interval.

Burst 1

Burst 1

Burst 2

Burst 2

Burst 3

Burst 3

Processing

& Sleep

DRDY

Burst 1

Burst 2

Burst 3

Burst 1

Burst 1

Burst 2

Burst 2

Burst 3

Burst 3

Processing

& Sleep

SCK

DRDY

Burst 1

Burst 2

Burst 3