SX8644I05AWLTRT Semtech, SX8644I05AWLTRT Datasheet - Page 10

• Manufacturer Part Number: SX8644I05AWLTRT
• Description: 12-ch Capacitive Touch Solution (Button & Slider)
• Manufacturer: Semtech

SX8644
Ultra Low Power, Capacitive Button and Slider
Touch Controller (12 sensors) with Enhanced LED Drivers
WIRELESS & SENSING
DATASHEET
3 F
UNCTIONAL DESCRIPTION
3.1 Quickstart Application
The SX8644 is preconfigured (Quickstart Application) for an application with 6 buttons, a slider (consisting of 6
sensors) and 8 LED drivers using logarithmic PWM fading.
Implementing a schematic based on Figure 6 will be immediately operational after powering without programming
the SX8644 (even without host).
SX8644
HOST
Quickstart Application
Figure 6
Touching the sensor on the CAP0 pin will enable automatically the LED connected to GPIO0. When the CAP0
sensor is released the LED on GPIO0 will slowly fade-out using smooth logarithmic fading.
All other sensors (CAP1 to CAP5) have their own LED associated on a GPIO pin showing a touch or a release.
The sensors on CAP6 to CAP11 are used in a slider configuration. A moving finger on the slider will enable the
LED on GPIO6 or GPIO7 indicating the finger movement.
The sensor detection and the LED fading described above are operational without any host interaction.
This is made possible using the SX8644 Autolight feature described in the following sections.
3.2
Introduction
3.2.1
General
The SX8644 is intended to be used in applications which require capacitive sensors covered by isolating overlay
material. A finger approaching the capacitive sensors will change the charge that can be loaded on the sensors.
The SX8644 measures the change of charge and converts that into digital values (ticks). The larger the charge on
the sensors, the larger the number of ticks will be. The charge to ticks conversion is done by the SX8644 Analog
Sensor Interface (ASI).
The ticks are further processed by the SX8644 and converted in a high level, easy to use information for the
user’s host.
Revision 7_6, October 12
© 2012 Semtech Corp.
www.semtech.com
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