sx8643 Semtech Corporation, sx8643 Datasheet - Page 10

• Manufacturer Part Number: sx8643
• Description: Ultra Low Power, Capacitive Button Touch Controller 12 Sensors With Enhanced Led Drivers
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
3 F
3.1 Quickstart Application
The SX8643 is preconfigured (Quickstart Application) for an application with eight buttons and eight LED drivers
using logarithmic PWM fading.
Implementing a schematic based on Figure 6 will be immediately operational after powering without programming
the SX8643 (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 CAP11) have their own LED associated on a GPIO pin showing a touch or a release.
The sensor detection and the LED fading described above are operational without any host interaction.
This is made possible using the SX8643 Autolight feature described in the following sections.
3.2
3.2.1
The SX8643 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 SX8643 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 SX8643 Analog
Sensor Interface (ASI).
The ticks are further processed by the SX8643 and converted in a high level, easy to use information for the
user’s host.
The information between SX8643 and the user’s host is passed through the I2C interface with an additional
interrupt signal indicating that the SX8643 has new information. For buttons this information is simply touched or
released.
Revision 7_5, February 10
UNCTIONAL DESCRIPTION
Introduction
General
d0
d1
d2
d3
d4
d5
d6
d7
cap10
cap2
cap3
cap4
cap5
cap6
cap7
cap8
cap9
cap0
cap1
interface
analog
sensor
Figure 6
generation
processor
micro
clock
RAM
ROM
power management
RC
© 2010 Semtech Corp.
controller
controller
Ultra Low Power, Capacitive Button Touch Controller
Quickstart Application
PWM
GPIO
NVM
SX8643
LED
I2C
10
gnd
gpio5
gpio4
gpio3
gpio2
gnd
gpio1
gpio0
bottom plate
d7
d5
d3
d1
(12 sensors) with Enhanced LED Drivers
d6
d4
d2
d0
HOST
DATASHEET
www.semtech.com
SX8643