sx8638 Semtech Corporation, sx8638 Datasheet - Page 10

• Manufacturer Part Number: sx8638
• Description: Low Power, Capacitive Button And Slider Touch Controller 8 Sensors With Enhanced Led Drivers And Proximity
• Manufacturer: Semtech Corporation

ADVANCED COMMUNICATIONS & SENSING
3 F
3.1 Quickstart Application
The SX8638 is preconfigured (Quickstart Application) for an application with 2 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 SX8638 (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 sensor CAP1 has its LED associated on pin GPIO1 showing a touch or a release.
The sensors on CAP2 to CAP7 are used in a slider configuration. A finger on the slider will enable the LED on
GPIO2 to GPIO7 indicating the finger slider position.
The sensor detection and the LED fading described above are operational without any host interaction.
This is made possible using the SX8638 Autolight feature described in the following sections.
3.2
3.2.1
The SX8638 is intended to be used in applications which require capacitive sensors covered by isolating overlay
material and which need to detect the proximity of a finger/hand though the air. A finger approaching the
capacitive sensors will change the charge that can be loaded on the sensors. The SX8638 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 SX8638 Analog Sensor Interface (ASI).
The ticks are further processed by the SX8638 and converted in a high level, easy to use information for the
user’s host.
Revision 7_6, September 10
UNCTIONAL DESCRIPTION
Introduction
General
d2
d3
d4
d5
d6
d7
d0
d1
cap0
cap1
cap2
cap3
cap4
cap5
cap6
cap7
interface
analog
sensor
Figure 6
generation
processor
micro
ROM
clock
RAM
power management
RC
© 2010 Semtech Corp.
Low Power, Capacitive Button and Slider Touch Controller
controller
controller
Quickstart Application
(8 sensors) with Enhanced LED Drivers and Proximity
PWM
GPIO
NVM
SX8638
LED
I2C
10
gnd
gpio5
gpio4
gpio3
gpio2
gnd
gpio1
gpio0
bottom plate
d5
d3
d7
d1
d0
d6
d4
d2
HOST
DATASHEET
www.semtech.com
SX8638