SX8645I05AWLTRT Semtech, SX8645I05AWLTRT Datasheet - Page 10

• Manufacturer Part Number: SX8645I05AWLTRT
• Description: 12-ch Capacitive Touch Solution (Button & Wheel)
• Manufacturer: Semtech

ADVANCED COMMUNICATIONS & SENSING
3 F
3.1 Quickstart Application
The SX8645 is preconfigured (Quickstart Application) for an application with 6 buttons, a wheel (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 SX8645 (even without host).
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 wheel configuration. A moving finger on the wheel will enable the
LED on GPIO6 or GPIO7 indicating the finger rotation direction.
The sensor detection and the LED fading described above are operational without any host interaction.
This is made possible using the SX8645 Autolight feature described in the following sections.
3.2
3.2.1
The SX8645 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 SX8645 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 SX8645 Analog
Sensor Interface (ASI).
The ticks are further processed by the SX8645 and converted in a high level, easy to use information for the
user’s host.
Revision 7_5, February 10
UNCTIONAL DESCRIPTION
Introduction
General
d0
d1
d2
d3
d4
d5
d6
d7
cap2
cap3
cap4
cap5
cap6
cap7
cap8
cap9
cap10
cap11
cap0
cap1
interface
analog
sensor
Figure 6
generation
processor
micro
clock
RAM
ROM
Touch Controller (12 sensors) with Enhanced LED Drivers
power management
RC
© 2010 Semtech Corp.
controller
controller
Quickstart Application
SX8645
PWM
GPIO
NVM
LED
I2C
10
Ultra Low Power, Capacitive Button and Wheel
gnd
gpio5
gpio4
gpio3
gpio2
gnd
gpio1
gpio0
bottom plate
d5
d3
d7
d1
d0
d6
d4
d2
HOST
DATASHEET
www.semtech.com
SX8645