QST108 datasheet(12/51 Pages) STMICROELECTRONICS

Part #	QST108

Description	Capacitive touch sensor device 8 keys with individual key state outputs or I2C interface

PDF	51 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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QST touch sensing technology

QST108

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Figure 4 illustrates an example of the drift compensation algorithm following a temperature

change.

Figure 4.

Drift compensation example

3.11

Adjacent key suppression (AKS™)

Adjacent key suppression (AKS™) is a Quantum-patented feature which prevents multiple

keys from responding to a single touch. This can happen with closely spaced keys, or a

scroll wheel that has buttons very near it.

The QST108 supports two AKS modes:

●

Locking AKS

Once a key is considered as “touched”, all other keys are locked in an untouched state.

To unlock these keys, the touched key must return to an untouched state. Then, the key

having the lowest key ID number is declared as the “touched” one.

●

Unlocking AKS

On each acquisition, the signal strengths from each key are compared and the key with

the highest signal level is declared as the “touched” one.

In I2C mode, up to 8 AKS groups can be specified.

Note:

All keys belonging to the same AKS group must have the same AKS mode.

Reference + DeTh

Reference Count

Reference Count + PosRelTh

Time

Drift Compensation

Temperature Change

QST108 Datasheet(PDF) 12 Page - STMicroelectronics