SX8644
Ultra Low Power, Capacitive Button and Slider
Touch Controller (12 sensors) with Enhanced LED Drivers
ADVANCED COMMUNICATIONS & SENSING
G
ENERAL
D
ESCRIPTION
The SX8644 is an ultra low power, fully integrated
12-channel solution for capacitive touch-buttons and
slider applications. Unlike many capacitive touch
solutions, the SX8644 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 SX8644 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 SX8644 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 SX8644 supports the 400 kHz I²C serial bus
data protocol and includes a field programmable
slave address. The SX8644 is available in a tiny
MLPQ 5mm x 5mm and a LQFP 7mm x 7mm
package. The small footprints make 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 Twelve Sensors Capacitive Touch Controller for
Buttons and Slider
Pre-configured for 6 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)
220uA (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
SX8644I05AWLTRT
1
-40°C to +85°C Lead Free MLPQ-W32
SX8644I05ALPTRT
2
-40°C to +85°C
1
2
Lead Free LQFP32
3000 Units/reel
2500 Units/reel
* This device is RoHS/WEEE compliant and Halogen Free
Revision 7_5, February 11
© 2011 Semtech Corp.
1
www.semtech.com
SX8644
Ultra Low Power, Capacitive Button and Slider
Touch Controller (12 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
1.6
1.7
G
ENERAL
D
ESCRIPTION
............................................................................................................... 4
Pin Diagram MLPQ
Marking information MLPQ
Pin Diagram LQFP
Marking information LQFP
Pin Description
Simplified Block Diagram
Acronyms
4
4
5
5
6
7
7
2
2.1
2.2
2.3
2.4
E
LECTRICAL
C
HARACTERISTICS
................................................................................................. 8
Absolute Maximum Ratings
Recommended Operating Conditions
Thermal Characteristics
Electrical Specifications
8
8
8
9
3
3.1
3.2
F
UNCTIONAL DESCRIPTION
........................................................................................................ 11
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
11
11
11
12
12
12
13
13
15
16
16
16
18
19
20
20
22
22
22
23
23
23
24
25
© 2011 Semtech Corp.
2
www.semtech.com
Revision 7_5, February 11
SX8644
Ultra Low Power, Capacitive Button and Slider
Touch Controller (12 sensors) with Enhanced LED Drivers
ADVANCED COMMUNICATIONS & SENSING
3.15.1 Power up
3.15.2 Assertion
3.15.3 Clearing
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
26
27
27
28
31
32
4
4.1
4.2
4.3
4.4
4.5
P
IN DESCRIPTIONS
..................................................................................................................... 33
Introduction
ASI pins
Host interface pins
Power management pins
General purpose IO pins
33
33
34
37
38
5
5.1
5.2
5.3
5.4
5.5
5.6
5.7
D
ETAILED
C
ONFIGURATION DESCRIPTIONS
.............................................................................. 39
Introduction
General Parameters
Capacitive Sensors Parameters
Button Parameters
Slider Parameters
Mapping Parameters
GPIO Parameters
39
42
43
48
52
56
59
6
6.1
6.2
6.3
6.4
6.5
6.6
I2C I
NTERFACE
........................................................................................................................... 63
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
63
64
65
66
69
71
72
73
74
7
8
8.1
8.2
8.3
8.4
A
PPLICATION
I
NFORMATION
...................................................................................................... 75
P
ACKAGING
I
NFORMATION
........................................................................................................ 76
Package Outline Drawing MLPQ-W32
Land Pattern MLPQ-W32
Package Outline Drawing LQFP32
Land Pattern LQFP32
76
76
77
77
Revision 7_5, February 11
© 2011 Semtech Corp.
3
www.semtech.com
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