sx8649 Semtech Corporation, sx8649 Datasheet - Page 10

• Manufacturer Part Number: sx8649
• Description: Ultra Low Power, Capacitive Button And Wheel Touch Controller 8 Sensors With Enhanced Led Drivers
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
3 F
3.1 Quickstart Application
The SX8649 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 SX8649 (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.
The other sensors (CAP1, CAP2 and CAP3) have their own LED associated on a GPIO pin showing a touch or a
release.
The sensors on CAP4 to CAP7 are used in a wheel configuration. A finger on the wheel will enable one of the
LEDs on GPIO4 to GPIO7 indicating the wheel segment touched. In the quickstart application the wheel is divided
into 4 segments
The sensor detection and the LED fading described above are operational without any host interaction.
This is made possible using the SX8649 Autolight feature described in the following sections.
3.2
3.2.1
The SX8649 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 SX8649 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 SX8649 Analog
Sensor Interface (ASI).
Revision 7_6, February 10
UNCTIONAL DESCRIPTION
Introduction
General
d7
d0
d1
d2
d3
d6
d4
d5
cap0
cap1
cap2
cap3
cap4
cap5
cap6
cap7
interface
analog
sensor
Figure 6
generation
processor
micro
clock
RAM
ROM
power management
RC
© 2010 Semtech Corp.
Touch Controller (8 sensors) with Enhanced LED Drivers
controller
controller
Quickstart Application
PWM
GPIO
NVM
SX8649
LED
I2C
10
Ultra Low Power, Capacitive Button and Wheel
gnd
gpo5
gpo4
gpo3
gpo2
gnd
gpo1
gpo0
bottom plate
d5
d3
d7
d1
d0
d6
d4
d2
HOST
DATASHEET
www.semtech.com
SX8649