SX8661 datasheet(24/88 Pages) SEMTECH

24 / 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

3.11 Processing

The first processing step of the raw ticks, coming out of the ASI, is low pass filtering to obtain an estimation of the

average capacitance: tick-ave (see Figure 19).

This slowly varying average is important in the detection of slowly changing environmental changes.

ticks (raw)

compensation DCV

ASI

processing

low pass

tick-diff

tick-ave

processing

GPIO

controller

PWM LED

controller

I2C

SPM

Figure 19

Processing

The difference of the tick average and the raw ticks, tick-diff, is a good estimation of rapid changing input

capacitances.

The tick-diff, tick-ave and the configuration parameters in the SPM are then processed and determines the sensor

information, I2C registers status and PWM control.

3.12 Configuration

Figure 20 shows the building blocks used for configuring the SX8661.

Figure 20

Configuration

The default configuration parameters of the SX8661 are stored in the Quick Start Memory (QSM). This

configuration data is setup to a very common application for the SX8661 with 8 buttons. Without any programming

or host interaction the SX8661 will start up in the Quick Start Application.

The QSM settings are fixed and cannot be changed by the user.

SX8661 Datasheet(PDF) 24 Page - Semtech Corporation