SX8661 datasheet(16/88 Pages) SEMTECH

16 / 88 page

ADVANCED COMMUNICATIONS & SENSING

DATASHEET

Revision v3.2, January 2011

www.semtech.com

SX8661

Low Power, Capacitive Button Touch and Proximity Controller

(8 sensors) with LED Drivers and Analog Output

Active mode offers fast scan periods. The typical reaction time is 30ms. All enabled sensors are scanned and

information data is processed within this interval.

Doze mode increases the scan period time which increases the reaction time to 195ms typical and at the same

time reduces the operating current.

Sleep mode turns the SX8661 OFF, except for the I2C peripheral, minimizing operating current while maintaining

the power supplies. In Sleep mode the SX8661 does not do any sensor scanning. The Sleep mode will be exited

by any I2C access.

The user can specify other scan periods for the Active and Doze mode and decide for other compromises

between reaction time and power consumption.

In most applications the reaction time needs to be fast when fingers are present, but can be slow when no person

uses the application. In case the SX8661 is not used for a specific time it will go from Active mode into Doze

mode and power will be saved. This time-out is determined by the Passive Timer which can be configured by the

user or turned OFF if not required.

To leave Doze mode and enter Active mode this can be done by a simple touch on any button.

The host can decide to force the operating mode by issuing commands over the I2C (using register GpioOpMode)

and take fully control of the SX8661. The diagram in Figure 9 shows the available operation modes and the

possible transitions.

Figure 9

Operation modes

3.5

Sensors on the PCB

The capacitive sensors are relatively simple copper areas on the PCB connected to the eight SX8661 capacitive

sensor input pins (CAP0…CAP7).The sensors are covered by isolating overlay material (typically 1mm...3mm).

The area of a sensor is typically one square centimetre which corresponds about to the area of a finger touching

the overlay material. The area of a proximity sensor is usually a factor larger as the smaller touch sensors.

The capacitive sensors can be setup as ON/OFF buttons for touch sensing and CAP0 offers additionally proximity

sensing (see example Figure 10) for control applications.

SX8661 Datasheet(PDF) 16 Page - Semtech Corporation