SX8661Z datasheet(15/87 Pages) SEMTECH

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ADVANCED COMMUNICATIONS & SENSING

DATASHEET

Revision v4.0, February 2016

www.semtech.com

SX8661Z

Low Power, Capacitive Button Touch and Proximity Controller

(8 sensors) with LED Drivers and Analog Output

Figure 8

PCB top layer of three touch buttons sensors surrounded by a proximity sensor

Please refer to the layout guidelines application note [1], for more details.

3.5

Button Information

The touch buttons have two simple states (see Figure 9): ON (touched by finger) and OFF (released and no finger

press).

off

Figure 9

Buttons

A finger is detected as soon as the number of ticks from the ASI reaches a user-defined threshold plus a

hysteresis.

A release is detected if the tick from the ASI goes below the threshold minus a hysteresis. The hysteresis around

the threshold avoids rapid touch and release signalling during transients.

Buttons can also be used to do proximity sensing. The principle of proximity sensing operation is exactly the same

as for touch buttons except that proximity sensing is done several centimeters above the overlay through the air.

ON state means that finger/hand is detected by the sensor and OFF state means the finger/hand is far from the

sensor and not detected.

3.6

Buzzer

The SX8661Z has the ability to drive a buzzer (on GPIO5) to provide an audible indication that a button has been

touched. The buzzer is driven by a square signal for approximately 30ms (default). During the first phase (15ms)

the signal’s frequency is default 4KHz while in the second phase (15ms) the signal’s frequency default is 8KHz.

The buzzer is activated only once during any button touch and is not repeated for long touches. The user can

choose to enable or disable the buzzer by configuration and define the idle level, frequencies and phase durations

(see 5.7).

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