SX8648
Ultra Low Power, Capacitive Button and Slider
Touch Controller (8 sensors) with Enhanced LED Drivers
ADVANCED COMMUNICATIONS & SENSING
G
ENERAL
D
ESCRIPTION
The SX8648 is an ultra low power, fully integrated 8-
channel solution for capacitive touch-buttons and
slider applications. Unlike many capacitive touch
solutions, the SX8648 features dedicated capacitive
sense inputs (that requires no external components)
in addition to 8 general purpose I/O ports (GPIO).
Each GPIO is typically configured as LED driver with
independent PWM source for enhanced lighting
control such as intensity and fading.
The SX8648 includes a capacitive 10 bit ADC analog
interface with automatic compensation up to 100pF.
The high resolution capacitive sensing supports a
wide variety of touch pad sizes and shapes and
allows capacitive buttons to be created using thick
overlay materials (up to 5mm) for an extremely
robust and ESD immune system design.
The SX8648 incorporates a versatile firmware that
was specially designed to simplify capacitive touch
solution design and offers reduced time-to-market.
Integrated
multi-time
programmable
memory
provides the ultimate flexibility to modify key firmware
parameters (gain, threshold, scan period, auto offset
compensation… ) in the field without the need for
new firmware development.
The SX8648 supports the 400 kHz I²C serial bus
data protocol and includes a field programmable
slave address. The tiny 4mm x 4mm footprint makes
it an ideal solution for portable, battery powered
applications where power and density are at a
premium.
DATASHEET
K
EY
P
RODUCT
F
EATURES
Complete Eight Sensors Capacitive Touch Controller for
Buttons and Slider
Pre-configured for 2 Buttons and a Slider
8 LED Drivers with Individual Intensity, Fading Control
and Autolight Mode
256 steps PWM Linear and Logarithmic control
High Resolution Capacitive Sensing
Up to 100pF of Offset Capacitance Compensation at
Full Sensitivity
Capable of Sensing through Overlay Materials up to
5mm thick
Extremely Low Power Optimized for Portable Application
8uA (typ) in Sleep Mode
80uA (typ) in Doze Mode (Scanning Period 195ms)
175uA (typ) in Active Mode (Scanning Period 30ms)
Programmable Scanning Period from 15ms to 1500ms
Auto Offset Compensation
Eliminates False Triggers due to Environmental
Factors (Temperature, Humidity)
Initiated on Power-up and Configurable Intervals
Multi-Time In-Field Programmable Firmware Parameters
for Ultimate Flexibility
On-chip user programmable memory for fast, self
contained start-up
"Smart" Wake-up Sequence for Easy Activation from Doze
No External Components per Sensor Input
Internal Clock Requires No External Components
Differential Sensor Sampling for Reduced EMI
400 KHz Fast-Mode I²C Interface with Interrupt
-40°C to +85°C Operation
T
YPICAL
A
PPLICATION CIRCUIT
A
PPLICATIONS
Notebook/Netbook/Portable/Handheld computers
Cell phones, PDAs
Consumer Products, Instrumentation, Automotive
Mechanical Button Replacement
O
RDERING
I
NFORMATION
Part Number
Temperature
Range
Package
SX8648I05AULTRT
1
-40°C to +85°C Lead Free MLPQ-UT28
1
3000 Units/reel
* This device is RoHS/WEEE compliant and Halogen Free
Revision 7_4, February 10
© 2010 Semtech Corp.
1
www.semtech.com
SX8648
Ultra Low Power, Capacitive Button and Slider
Touch Controller (8 sensors) with Enhanced LED Drivers
ADVANCED COMMUNICATIONS & SENSING
Table of Contents
DATASHEET
G
ENERAL
D
ESCRIPTION
........................................................................................................................ 1
T
YPICAL
A
PPLICATION CIRCUIT
............................................................................................................ 1
K
EY
P
RODUCT
F
EATURES
..................................................................................................................... 1
A
PPLICATIONS
....................................................................................................................................... 1
O
RDERING
I
NFORMATION
...................................................................................................................... 1
1
1.1
1.2
1.3
1.4
1.5
G
ENERAL
D
ESCRIPTION
............................................................................................................... 4
Pin Diagram
Marking information
Pin Description
Simplified Block Diagram
Acronyms
4
4
5
6
6
2
2.1
2.2
2.3
2.4
E
LECTRICAL
C
HARACTERISTICS
................................................................................................. 7
Absolute Maximum Ratings
Recommended Operating Conditions
Thermal Characteristics
Electrical Specifications
7
7
7
8
3
3.1
3.2
F
UNCTIONAL DESCRIPTION
........................................................................................................ 10
Quickstart Application
Introduction
3.2.1
General
3.2.2
GPIOs
3.2.3
Parameters
3.2.4
Configuration
3.3
Scan Period
3.4
Operation modes
3.5
Sensors on the PCB
3.6
Button and Slider Information
3.6.1
Button Information
3.6.2
Slider Information
3.7
Analog Sensing Interface
3.8
Offset Compensation
3.9
Processing
3.10
Configuration
3.11
Power Management
3.12
Clock Circuitry
3.13
I2C interface
3.14
Reset
3.14.1 Power up
3.14.2 RESETB
3.14.3 Software Reset
3.15
Interrupt
3.15.1 Power up
3.15.2 Assertion
3.15.3 Clearing
10
10
10
11
11
11
12
12
14
15
15
15
17
18
19
19
21
21
21
22
22
22
23
24
24
24
24
© 2010 Semtech Corp.
2
www.semtech.com
Revision 7_4, February 10
SX8648
Ultra Low Power, Capacitive Button and Slider
Touch Controller (8 sensors) with Enhanced LED Drivers
ADVANCED COMMUNICATIONS & SENSING
3.15.4 Example
3.16
General Purpose Input and Outputs
3.16.1 Introduction and Definitions
3.16.2 GPI
3.16.3 GPP
3.16.4 GPO
3.16.5 Intensity index vs PWM pulse width
3.17
Smart Wake Up
DATASHEET
25
25
25
26
26
27
30
31
4
4.1
4.2
4.3
4.4
4.5
P
IN DESCRIPTIONS
..................................................................................................................... 32
Introduction
ASI pins
Host interface pins
Power management pins
General purpose IO pins
32
32
33
36
37
5
5.1
5.2
5.3
5.4
5.5
5.6
5.7
D
ETAILED
C
ONFIGURATION DESCRIPTIONS
.............................................................................. 38
Introduction
General Parameters
Capacitive Sensors Parameters
Button Parameters
Slider Parameters
Mapping Parameters
GPIO Parameters
38
41
42
47
51
55
58
6
6.1
6.2
6.3
6.4
6.5
6.6
I2C I
NTERFACE
........................................................................................................................... 62
I2C Write
I2C read
I2C Registers Overview
Status Registers
Control Registers
SPM Gateway Registers
6.6.1
SPM Write Sequence
6.6.2
SPM Read Sequence
6.7
NVM burn
62
63
64
65
68
70
71
72
73
7
8
8.1
8.2
A
PPLICATION
I
NFORMATION
...................................................................................................... 74
P
ACKAGING
I
NFORMATION
........................................................................................................ 75
Package Outline Drawing
Land Pattern
75
75
Revision 7_4, February 10
© 2010 Semtech Corp.
3
www.semtech.com
SX8648
Ultra Low Power, Capacitive Button and Slider
Touch Controller (8 sensors) with Enhanced LED Drivers
ADVANCED COMMUNICATIONS & SENSING
1 G
ENERAL
D
ESCRIPTION
1.1
Pin Diagram
resetb
gpio7
gpio6
cap0
vana
vdig
gnd
DATASHEET
28
cap1
cap2
cap3
cap4
cap5
cap6
cap7
1
2
3
4
5
27
26
25
24
23
22
SX8648
21
20
gnd
gpio5
gpio4
gpio3
gpio2
gnd
gpio1
Top View
19
18
17
6
7
8
cn
9
cp
10
vdd
bottom ground pad
11
intb
12
scl
13
sda
14
gpio0
16
15
Figure 1
Pinout Diagram
1.2
Marking information
8648
yyww
xxxxx
R05
yyww = Date Code
xxxxx = Semtech lot number
R05 = Semtech Code
Figure 2
Marking Information
Revision 7_4, February 10
© 2010 Semtech Corp.
4
www.semtech.com
SX8648
Ultra Low Power, Capacitive Button and Slider
Touch Controller (8 sensors) with Enhanced LED Drivers
ADVANCED COMMUNICATIONS & SENSING
1.3
Pin Description
Name
CAP1
CAP2
CAP3
CAP4
CAP5
CAP6
CAP7
CN
CP
VDD
INTB
SCL
SDA
GPIO0
GPIO1
GND
GPIO2
GPIO3
GPIO4
GPIO5
GND
GPIO6
GPIO7
VDIG
GND
RESETB
VANA
CAP0
DATASHEET
Number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
Type
Analog
Analog
Analog
Analog
Analog
Analog
Analog
Analog
Analog
Power
Digital Output
Digital Input
Digital Input/Output
Digital Input/Output
Digital Input/Output
Ground
Digital Input/Output
Digital Input/Output
Digital Input/Output
Digital Input/Output
Ground
Digital Input/Output
Digital Input/Output
Analog
Ground
Digital Input
Analog
Analog
Ground
Description
Capacitive Sensor 1
Capacitive Sensor 2
Capacitive Sensor 3
Capacitive Sensor 4
Capacitive Sensor 5
Capacitive Sensor 6
Capacitive Sensor 7
Integration Capacitor, negative terminal (1nF between CN and CP)
Integration Capacitor, positive terminal (1nF between CN and CP)
Main input power supply
Interrupt, active LOW, requires pull up resistor (on host or external)
I2C Clock, requires pull up resistor (on host or external)
I2C Data, requires pull up resistor (on host or external)
General Purpose Input/Output 0
General Purpose Input/Output 1
Ground
General Purpose Input/Output 2
General Purpose Input/Output 3
General Purpose Input/Output 4
General Purpose Input/Output 5
Ground
General Purpose Input/Output 6
General Purpose Input/Output 7
Digital Core Decoupling, connect to a 100nF decoupling capacitor
Ground
Active Low Reset. Connect to VDD if not used.
Analog Core Decoupling, connect to a 100nF decoupling capacitor
Capacitive Sensor 0
Exposed pad connect to ground
bottom plate GND
Table 1
Pin description
Revision 7_4, February 10
© 2010 Semtech Corp.
5
www.semtech.com
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