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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
GENERAL DESCRIPTION
The SX 8649 is an ultra lo w power, full y integr ated 8-
channel solution for capacitive touch-buttons and
wheel applications. Unlike many capacitive touch
solutions, the SX8649 features dedicated capacitive
sense inputs (that requires no external components)
in addition to 8 general purpose I/O ports (GPIO).
Each GPIO is typicall y conf igured as LED dri ver with
independent PWM source for enhanced lighting
control such as intensity and fading.
The SX 8649 i nclu des a c a pac it iv e 1 0 b it ADC an alo g
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 SX8649 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 SX8649 supports the 400 kHz I²C serial bus
data protocol and includes a field programmable
slave a ddress. The ti ny 4mm x 4mm footprint m akes
it an ideal solution for portable, battery powered
applications where power and density are at a
premium.
TYPIC AL APPLIC ATION CIRCUIT
KEY PRODUCT FEATURES
Complete Eight Sensors Capacitive Touch Controller for
Butto ns and Wheel
Pre-configured for 4 Buttons and a Wheel
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
APPLICATIONS
Notebook/Netbook/Portable/Handheld computers
Cell phones, PDAs
Consumer Products, Instrumentation, Automotive
Mechanical Button Replacement
ORDERING INFORMATION
Part Number Temperature
Range Package
SX8649I05AULTRT1 -40°C to +85°C Lead Free MLPQ-UT28
1 3000 Units/reel
* This device is RoHS/WEEE compliant and Halogen Free
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
Table of Contents
GENERAL DESCRIPTION........................................................................................................................1
TYPIC AL APPLIC ATION CIRCUIT............................................................................................................1
KEY PRODUCT FEATURES.....................................................................................................................1
APPLICATIONS.......................................................................................................................................1
ORDERING INFORMATION......................................................................................................................1
1 GENERAL DESCRIPTION...............................................................................................................4
1.1 Pin Diagram 4
1.2 Marking information 4
1.3 Pin Description 5
1.4 Simplified Block Diag ram 6
1.5 Acronyms 6
2 ELECTRICAL CHARACTERISTICS .................................................................................................7
2.1 Absolute Maximum Ratings 7
2.2 Recommended Operating Conditions 7
2.3 Thermal Characteristics 7
2.4 Electrical Specifications 8
3 FUNCTIONAL DESCRIPTION........................................................................................................10
3.1 Quickst art Application 10
3.2 Introduction 10
3.2.1 General 10
3.2.2 GPIOs 11
3.2.3 Parameters 11
3.2.4 Configuration 11
3.3 Scan Pe rio d 12
3.4 Operation modes 12
3.5 Sensors on the PCB 14
3.6 Button and Wheel Information 15
3.6.1 Button Information 15
3.6.2 Wheel Information 15
3.7 Analog Sensing Interface 17
3.8 Offset Compensation 18
3.9 Processing 19
3.10 Configuration 19
3.11 Power Management 21
3.12 Clock Circuitry 21
3.13 I2C interface 21
3.14 Reset 22
3.14.1 Power up 22
3.14.2 RESETB 22
3.14.3 Software Reset 23
3.15 Interrupt 24
3.15.1 Power up 24
3.15.2 Assertion 24
3.15.3 Clearing 24
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
3.15.4 Example 25
3.16 General Purpose Input and Outputs 25
3.16.1 Introduction and Definitions 25
3.16.2 GPI 26
3.16.3 GPP 26
3.16.4 GPO 27
3.16.5 Intensity index vs PWM pulse width 30
3.17 Smart Wake Up 31
4 PIN DESCRIPTIONS.....................................................................................................................32
4.1 Introduction 32
4.2 ASI pins 32
4.3 Host interface pins 33
4.4 Power management pins 36
4.5 General purpose IO pins 37
5 DETAILED CONFIGURATION DESCRIPTIONS ..............................................................................38
5.1 Introduction 38
5.2 General Parameters 41
5.3 Capacitiv e Sen sors Para met ers 42
5.4 Button Parameters 47
5.5 Wheel Parameters 51
5.6 Mapping Parameters 56
5.7 GPIO Parameters 59
6 I2C INTERFACE...........................................................................................................................63
6.1 I2C Write 63
6.2 I2C read 64
6.3 I2C Registers Overview 65
6.4 Status Registers 66
6.5 Control Registers 69
6.6 SPM Gateway Registers 71
6.6.1 SPM Write Sequence 72
6.6.2 SPM Read Sequence 73
6.7 NVM burn 74
7 APPLIC ATION INFORMATION......................................................................................................75
8 PACKAGING INFORMATION ........................................................................................................76
8.1 Package Outline Drawing 76
8.2 Land Pattern 76
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
1 GENERAL DESCRIPTION
1.1 Pin Diagram
SX8649
Top View
1
2
3
4
5
6
7
21
20
19
18
17
16
15
8 9 10 11 12 13 14
22232425262728
bott om gr ound pa d
cap2
cap3
cap4
cap5
cap6
cap7
gnd
gpio5
gpio4
gpio3
gpio2
gpio1
gnd
gpio0
cap1
cap0
vana
resetb
gnd
gpio7
vdig
gpio6
cn
cp
vdd
scl
intb
sda
Figure 1 Pinout Diagram
1.2 Marking information
8649
yyww
xxxxx
R05
yyww = Date Code
xxxxx = Semtech lot number
R05 = Semtech Code
Figure 2 Marking Inform ation
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
1.3 Pin Description
Number Name Type Description
1 CAP1 Analog Capacitive Sensor 1
2 CAP2 Analog Capacitive Sensor 2
3 CAP3 Analog Capacitive Sensor 3
4 CAP4 Analog Capacitive Sensor 4
5 CAP5 Analog Capacitive Sensor 5
6 CAP6 Analog Capacitive Sensor 6
7 CAP7 Analog Capacitive Sensor 7
8 CN Analog Integration Capacitor, negative terminal (1nF between CN and CP)
9 CP Analog Integration Capacitor, positive terminal (1nF between CN and CP)
10 VDD Power Main input power supply
11 INTB Digital Output Interrupt, active LOW, requires pull up resistor (on host or external)
12 SCL Digital Input I2C Clock, requires pull up resistor (on host or external)
13 SDA Digital Input/Output I2C Data, requires pull up resistor (on host or external)
14 GPIO0 Digital Input/Output General Purpose Input/Output 0
15 GPIO1 Digital Input/Output General Purpose Input/Output 1
16 GND Ground Ground
17 GPIO2 Digital Input/Output General Purpose Input/Output 2
18 GPIO3 Digital Input/Output General Purpose Input/Output 3
19 GPIO4 Digital Input/Output General Purpose Input/Output 4
20 GPIO5 Digital Input/Output General Purpose Input/Output 5
21 GND Ground Ground
22 GPIO6 Digital Input/Output General Purpose Input/Output 6
23 GPIO7 Digital Input/Output General Purpose Input/Output 7
24 VDIG Analog Digital Core Decoupling, connect to a 100nF decoupling capacitor
25 GND Ground Ground
26 RESETB Digital Input Active Low Reset. Connect to VDD if not used.
27 VANA Analog Analog Core Decoupling, connect to a 100nF decoupling capacitor
28 CAP0 Analog Capacitive Sensor 0
bottom plate GND Ground Exposed pad connec t to ground
Table 1 P in descr ipt ion
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
1.4 Simplified Block Diagram
The simplified block diagram of the SX8649 is illustrated in Figure 3.
vana
resetb
gnd
gpo7
vdig
gpo6
cn
cp
vdd
scl
intb
sda
Figure 3 Simplified block diagram of the SX8649
1.5 Acronyms
ASI Analog Sensor Interface
DCV Digital Compensation Value
GPI General Purpose Input
GPO General Purpose Output
GPP General Purpose PWM
MTP Multiple Time Programmable
NVM Non Volatile Memor y
PWM Pulse Width Modulation
QSM Quick Start Memory
SPM Shadow Parameter Memory
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
2 ELECTRICAL CHARACTERISTICS
2.1 Absolute Maximum Ratings
Stresses above the values listed in “Absolute Maximum Ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of the device at these, or any other conditions beyond the “Recommended
Operating Conditions”, is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device
reliability.
Parameter Symbol Min. Max. Unit
Supply Voltage VDD -0.5 3.9 V
Input voltage (non-supply pins) VIN -0.5 3.9 V
Input current (non-supply pins) IIN 10 mA
Operating Junction Temperature TJCT 125 °C
Reflow temperature TRE 260 °C
Storage temperature TSTOR -50 150 °C
ESD HBM (Human Body model)(i) ESDHBM 3 kV
Latchup(ii) I
LU ± 100 mA
Table 2 Absolute Maximum Ratings
(i) Tested to JEDEC standard JESD22-A114
(ii) Tested to JEDEC standard JESD78
2.2 Recommended Operating Conditions
Parameter Symbol Min. Max. Unit
Supply Voltage VDD 2.7V 3.6 V
Supply Voltage Drop(iii, iv, v) VDDdrop 100 mV
Supply Voltage for NVM programming VDD 3.0V 3.6 V
Ambient Temperature Range TA -40 85 °C
Table 3 Recom m ended Oper ating Conditions
(iii) Performance for 2.6V < VDD < 2.7V might be degraded.
(iv) Operation is not guaranteed below 2.6V. Should VDD briefly drop below this minimum value, then the SX8649 may
require;
- a hardware reset issued by the host using the RESETB pin
- a software reset issued by the host using the I2C interface
(v) In the event the host processor is reset or undergoes a power OFF/ON cycle, it is recommended that the host also resets
the SX8649 and assures that parameters are re-written into the SPM (should these differ to the parameters held in NVM).
2.3 Thermal Characteristics
Parameter Symbol Min. Max. Unit
Thermal Resistance - Junction to Ambient (vi) θJA 25 °C/W
Table 4 Ther m al Char acteristics
(vi) Static airflow
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
2.4 Electrical Specifications
All values are valid within the operating conditions unless otherwise specified.
Parameter Symbol Conditions Min. Typ. Max. Unit
Current consumption
Active mode, average IOP,active 30ms scan period,
8 sensors enabled,
minimum sensitivity
175
225 uA
Doze mode, average IOP,Doze 195ms scan period,
8 sensors enabled,
minimum sensitivity
80
110 uA
Sleep IOP,sleep I2C and GPI listening,
sensors disabled 8 17 uA
GPIO, set as Input, RESETB, SCL, SDA
Input logic high VIH 0.7*VDD VDD + 0.3V V
Input logic low VIL VSS applied to GND pins VSS - 0.3V 0.8 V
Input leakage current LI CMOS input ±1 uA
Pull up resistor RPU when enabled 660 kΩ
Pull down resistor RPD when enabled 660 kΩ
GPIO set as Output, INTB, SDA
Output logic high VOH I
OH <4mA VDD-0.4 V
Output logic low VOL I
OL,GPIO<12mA
IOL,SDA,INTB<4mA 0.4 V
Start-up
Power up time tpor time between rising edge
VDD and rising INTB 150 ms
RESETB
Pulse width tres 50 ns
External components
Capacitor between VDIG, GND Cvdig type 0402, tolerance +/-50% 100 nF
Capacitor between VANA, GND Cvana type 0402, tolerance +/-50% 100 nF
Capacitor between CP, CN Cint type 0402, tolerance +/-10% 1 nF
Capacitor between VDD, GND Cvdd type 0402, tolerance +/-50% 100 nF
Table 5 E lect rical Specifications
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
Parameter Symbol Conditions Min. Typ. Max. Unit
I2C Timing Specifications (i)
SCL clock frequency fSCL 400 KHz
SCL low period tLOW 1.3 us
SCL high period tHIGH 0.6 us
Data setup time tSU;DAT 100 ns
Data hold time tHD;DAT 0 ns
Repeated start setup time tSU;STA 0.6 us
Start condition hold time tHD;STA 0.6 us
Stop condition setup time tSU;STO 0.6 us
Bus free time between stop and start t
BUF 500 us
Input glitch sup pre ssi on tSP 50 ns
Table 6 I 2C Tim ing Specification
Notes:
(i) All timing specifications, Figure 4 and Figure 5, refer to voltage levels (VIL, VIH, VOL) defined in Table 5.
The interface complies with slave F/S mode as described by NXP: “I2C-bus specification, Rev. 03 - 19 June 2007”
Figure 4 I2C Start and Stop tim ing
Figure 5 I2C Data timing
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
3 FUNCTIONAL DESCRIPTION
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.
Implem enting a schem atic based on Fig ure 6 will be imm ediately oper ational after powering without progra mming
the SX8649 (e ven wit hout hos t).
HOST
SX8649
cap0
cap1
cap2
cap3
cap4
cap6
cap5
cap7
gnd
gpo5
gpo4
gpo3
gpo2
gpo1
gnd
gpo0
vana
resetb
gnd
gpo7
vdig
gpo6
cn
cp
analog
sensor
interface
micro
processor
RAM
ROM
NVM
I2C
GPIO
controller
power management
clock
generation
RC
PWM
LED
controller
bottom plate
d1
d0
d2
d3
d4
d5
d6
d7
d0
d1
d2
d3
d4
d5d6
d7
vdd
scl
intb
sda
Figure 6 Quickstart Application
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 s ensors (C AP1, CAP2 an d CAP3) h ave their own LE D associat ed on a G PIO pin sho wing 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 G PIO4 t o G PIO 7 i ndicat in g the wheel segment touched. In the quic kstart app lic at io n the whe el is d i vi ded
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 Introduction
3.2.1 General
The SX8649 is inten ded to be used in app lications which require capacitive sen sors covered by isolating overlay
material. A finger approaching the capacitive sensors will change the charge that can be loaded on the sensors.
The SX 8649 measur es the c hange of c harge and co nv erts that int o d igi tal val ues (tic ks). T he lar ger the charge on
the sensors , the larger the number of ticks will be. T he charge to tick s conversion is don e by the SX864 9 Analog
Sensor Interface (ASI).
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
The ticks are further processed by the SX8649 and converted in a high level, easy to use information for the
user’s host.
The information between SX8649 and the user’s host is passed through the I2C interface with an additional
interrupt signal indicat ing that the SX8649 has new information. For buttons this inf ormation is sim ply touched or
released.
3.2.2 GPIOs
A second path of feedback to the user is using General Purpose Input Output (GPIO) pins. The SX8649 offers
eight individual configurable GPIO pins. The GPIO can e.g. be set as a LED driver which slowly fade-in when a
finger touches a button and slowly fade-out when the button is released. Fading intensity variations can be
logarithmic or linear. Interval speed and initial and final light intensity can be selected by the user. The fading is
done using a 256 steps PWM. The SX8649 has eight individual PWM generators, one for each GPIO pin.
The LED fading can be initiated automatically by the SX8649 by setting the SX8649 Autolight feature. A simple
touch on a sensor and the corresponding LED will fade-in without any host interaction over the I2C.
In case the A utolight f eat ure is dis abled t hen th e hos t wil l decid e to s tart a LE D fadi ng-in p eriod, s im ply b y setting
the GP0 pin to ‘high’ using one I2C command. The SX8649 will then slowly fade-in the LED using the PWM
autonomously.
In case th e host needs to have f ull contr ol of the LED intensi ty the n the hos t can set the G PIO i n GPP m ode. T he
host is then able to set the PWM pulse width freely at the expense of an increased I2C occupation.
The GPIOs can be set further in the digital standard Input mode (GPI).
3.2.3 Parameters
The SX8649 has m any low level built-in, fixed algorithms and procedures. To allow a lot of freedom for the user
and adapt the SX8649 for different applications these algorithms and procedures can be configured with a large
set of parameters which will be described in the following sections. Examples of parameters are which sensors
are buttons or which sensors are parts of a wheel, which GPIO is used for outputs or LEDs and which GPIO is
mapped to which butt on.
Sensitivity and detection thresholds of the sensors are part of these parameters. Assuming that overlay material
and sensors areas are identical then the sensitivities and thresholds will be the same for each sensor. In case
sensors are not of the same size then sensitivities or thresholds might be chosen individually per sensor.
So a smaller size sensor can have a larger sensitivity while a big size sensor may have the lower sensitivity.
3.2.4 Configuration
During a development phase the parameters can be determined and fine tuned by the users and downloaded
over the I2C in a dynamic way. The parameter set can be downloaded over the I2C by the host each time the
SX8649 boots up. This allows a flexible way of setting the parameters at the expense of I2C occupation.
In case the parameters are frozen they can be programmed in Multiple Time Programmable (MTP) Non Volatile
Memory (NVM) on the SX8649. The programming needs to be done once (over the I2C). The SX8649 will then
boot up from the NVM and additional parameters from the host are not required anymore.
In case the host desires to over write the boot-up NVM param eters (partly or even complete) this can be done b y
additional I2C communications.
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
3.3 Scan Period
The basic operation Scan period of the SX8649 sensing interface can be split into three periods over time.
In the first period (Sensing) the SX8649 is sensing all enabled CAP inputs, from CAP0 towards CAP7.
In the sec o nd peri od ( Process ing) t he SX 86 49 pr ocesses the sensor d ata, ver ifie s and up dat es th e G PIO a n d I2 C
status registers.
In the third period (Timer) the SX8649 is set in a low power mode and waits until a new cycle starts.
Figure 7 shows the different SX8649 periods over time.
Figure 7 Scan Period
The s can peri od det erm ines the m inim um reaction tim e of th e SX 8649. T he s can per iod can be c onf igure d by t he
host from 15ms to values larger than a second.
The reaction time is defined as the interval between a touch on the sensor and the moment that the SX8649
generates the interrupt on the INTB pin. The shorter the scan period the faster the reaction time will be.
Very low po wer c ons umptio n c an be obt ai ned by sett in g very lo ng sc an p er io ds with th e expense of ha vi ng lo nger
reaction times.
Important: All external e ve nts like GPIO, I2C and INTB are upd ate d i n th e pr oce s s ing per iod , s o o nc e e very s can
period. If e.g. a GPI would change sta te direct ly after t he processin g period t hen this will be report ed with a d elay
of one scan period later in time.
3.4 Operation modes
The SX 8649 has 3 op eratio n m odes. T he main dif f erenc e is f ound in t he re action t im e (c orres ponding to t he s can
period) and power consumption.
Active mode offers fast scan periods. The typical reaction time is 30ms. All enabled sensors are scanned and
information data is processed within this interval.
Doze mode increases the scan period time which increases the reaction time to 195ms typical and at the same
time reduces the operating current.
Sleep mode turns the SX8649 OFF, except for the I2C and GPI peripheral, minimizing operating current while
maintaining the power supplies. In Sleep mode the SX8649 does not do any sensor scanning.
The user can specify other scan periods for the Active and Doze mode and decide for other compromises
between reaction time and power consumption.
In mos t applicati ons the re action t ime needs to be fas t when fing ers ar e present, but can be sl ow whe n no pers on
uses the application. In case the SX8649 is not used for a specific time it can go from Active mode into Doze
mode and p ower wi ll be sa ved. T his tim e-out is det erm ined by the Pas sive T imer which c an be c onfigur ed b y the
user or turned OFF if not required.
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
To leave Doze mode and enter Active mode this can be done by a simple touch on any button.
For some applications a single button touch might cause undesired wakening up and Active mode would be
entered too often.
The SX8649 offers therefore a smart wake-up sequence feature in which the user needs to touch and release a
correct sequence of buttons before Active m ode will be entered. T his is explained in m ore detail in the W ake-Up
Sequence section.
The host can decide to force the operating mode by issuing commands over the I2C (using register
CompOpMode) and take fully control of the SX8649.
The diagram in Figure 8 shows the available operation modes and the possible transitions.
Figure 8 Operation modes
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
3.5 Sensors on the PCB
The capacitive sensors are relativel y sim ple copper areas on the PCB connected to the eight SX8649 capacitive
sensor input pins (CAP0…CAP7).The sensors are covered by isolating overlay material (typically 1mm...3mm).
The area of a sensor is typicall y on e square cent imeter which c orresponds about to th e area of a fin ger touc hing
the overlay material.
The capacitive sensors can be setup as ON/OFF buttons (see example Figure 9) or arranged in a wheel
configuration (see example Figure 10) for e.g. menu scrolling or volume control applications.
Figure 9 PCB top layer of four sensors for buttons (surrounded by a ground plane)
Figure 10 PCB top layer of one wheel using six sensors (surrounded by ground plane)
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SX8649
Ultra Low Power, Capacitive Button and Wheel
Touch Controller (8 sensors) with Enhanced LED Drivers
3.6 Button and Wheel Information
3.6.1 Button Information
The buttons have two simple states (see Figure 11): ON (touched by finger) and OFF (released and no finger
press).
Figure 11 Buttons
A finger is detected as soon as the number of ticks from the ASI reaches a user-defined threshold plus a
hysteresis.
A release is detected if the ticks from the ASI go below the threshold minus a h ysteresis. The hysteresis around
the threshold avoids rapid touch and release signaling during transients.
3.6.2 Wheel Information
In case s ensor s are ar ranged in a whee l c onf ig ur at ion the O N, O FF inf or mation re mains available as if it wou l d be
a single sensor button.
Figure 12 Wheel ON, OFF
W herever the wheel is touched the inform ation will be s et to ON. If no fin ger is pres ent the wheel i nformatio n will
be OFF.
Due to the 2 dimensional character of the wheel more information can be derived by processing the ticks.
During a touch a finger will influence most of the time the charge on one or two sensors but never all of the
sensors at the same time. Some sensor ticks will be larger than others based on the finger position.
The processing algorithms can therefore determine where the finger is positioned on the wheel.
Interpolation between sensors increases the resolution beyond the number of sensors in the wheel.
The interp olation can be done already on th e PCB sens or structures (analog, l ike the wheel in Figure 10) and as
well by SX8649 digital processing of the ticks using center of gravity calculations.
The position of the finger on the PCB structures varies between the m inimum zero and a user defin ed maximum
(Figure 13).
....x...
position
min
max
Figure 13 W heel Posit ion
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The pos ition belongin g to the m inimum and as sociated to a s ensor is def ined arbitrar ily. The SX 8649 defin es the
minim um pos ition to t he se nsor with the lo west C AP p in index . E. g. if CA P0 is a butto n (or d isabled) a nd C AP1 to
CAP7 are the sensors of the wheel then the position ‘zero’ starts at CAP1 and the maximum is found at CAP7.
In addition to the wheel position, the SX8649 allows to detect finger rotation. The rotation occurs if the finger
position c hanges a certa in step size bet ween two succ eeding scan periods . A very slo w m oving finger wil l n ot be
considered as a rotation as the changing position will be minor. The SX8649 allows detecting a rotate clockwise
(direction min to max) (see Figure 14) and a rotate counter clockwise (direction max to min) (see Figure 15).
rotate clockwise
Figure 14 Wheel rotate clockwise
Figure 15 Wheel rotate counter clockwise
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3.7 Analog Sensing Interface
The Analog Sensing Interface (ASI) converts the charge on the sensors into ticks which will be further digitally
process ed. T he basic pr inci ple of the ASI will be expla i ned in this sect ion.
The ASI c onsists of a multiplexer s electing t he sensor, analog switc hes, a ref erence volt age, an ADC sigm a delta
converter, an offset compensation DAC and an external integration capacitor (see Figure 16).
switches
cap2
cap1
cap0 analog
multi-
plexor
Offset
compensation
DAC
ADC ticks (raw)
compensation DCV
ASI processing
Cint
voltage
reference
low pass
ticks-diff
ticks-ave
cap7
Figure 16 Analog Sensor Interface
To get the ticks representing the charge on a specific sensor the ASI will execute several steps.
The c harge on a s ensor c ap (e.g. C AP0) will be acc um ulated multip le tim es on the ex terna l integratio n capac itor,
Cint.
This results in an increasing voltage on Cint proportional to the capacitance on CAP0.
At this stage the offset compensation DAC is enabled. The compensation DAC generates a voltage proportional
to an estimation of the external capacitance. The estimation is obtained by the offset compensation procedure
executed e.g. at power-u p.
The difference between the DAC output and the charge on Cint is the desired signal. In the ideal case the
diff erence of char ge will be c onverted t o zero tic k s if no finger is present and the num ber of tick s becom es high in
case a finger is present.
The difference of charge on Cint and the DAC output will be transferred to the ADC (Sigma Delta Integrator).
After the charge transfer to the ADC the steps above will be repeated.
The larger the number the cycles are repeated the larger the signal out of the ADC with improved SNR. The
sensitivity is therefore directly related to the number of cycles.
The SX8649 allows setting the sensitivity for each sensor individually in applications which have a variety of
sensors sizes or diff erent overl ays or f or f ine-tunin g perf orm ances . The optim al sensitivi ty is de pending he avil y on
the final app licat ion . If the sens itiv it y is too low the tick s will not pass the thres holds and it is not p oss ible to detect
fingers. In case the sensi tivit y is set too large a f inger hov ering abov e the sensor s will alrea dy be detected bef ore
the finger really touches the overlay resulting in false detections.
Once the ASI has finished the first sensor, the ticks are stored and the ASI will start measuring the next sensor
until all (enabled) sensors pins have been treated.
In case some sensors are disabled then these result in lower power consumption simply because the ASI is active
for a shorter period and the following processing period will be shorter.
The ticks from the ASI will then be handled by the digital processing.
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3.8 Offset Compensation
The capacitance at the CAP pins is determined by an intrinsic capacitance of the integrated circuit, the PCB
traces, gr ound c ou pl ing an d the s ens or pl anes . This c apacitance is rel ati ve ly large and might become eas il y som e
tens of pF. This parasitic capacitance will vary only slowly over time due to environmental changes.
A finger touch is in the order of one pF. If the finger approaches the sensor this occurs typically fast.
The ASI has the difficult task to detect and distinguish a small, fast changing capacitance, from a large, slow
varying c apacitanc e. This woul d require a very precis e, high res olution AD C and com plicated, po wer consu ming,
digital processing.
The SX 8649 featur es a 16 bit DAC which c ompens ates f or the larg e, slow varyin g capacita nce alrea dy in f ront of
the ADC. In other words the ADC converts only the desired small signal. In the ideal world the ADC will put out
zero ticks even if the external capacitance is as high as 100pF.
At each power-up of the SX8649 the Digital Com pensation Values (DC V) are es timated by th e digital pr ocessing
algorithms. The algorithm will adjust the compensation values such that zero ticks will be generated by the ADC.
Once the correct compensation values are found these will be stored and used to compensate each CAP pin.
If the SX86 49 is s hut down the c ompens ation values will b e lost. At a n ext powe r-up the pr ocedure s tarts all o ver
again. T his assures th at the SX8649 will operate u nder an y con dition. Po weri ng up at e.g. d ifferent tem peratures
will not change the performance of the SX8649 and the host does not have to do anything special.
The DCVs do not need to be updated if the external conditions remain stable.
However if e.g. temperature changes this will influence the external capacitance. The ADC ticks will drift then
slowly around zero values basically because of the mismatch of the compensation circuitry and the external
capacitance.
In case the average value of the ticks become higher than the positive noise threshold (configurable by user) or
lower than the negative threshold (configurable by user) then the SX8649 will initiate a compensation procedure
and find a new set of DCVs.
Compensation procedures can as well be initiated by the SX8649 on periodic intervals. Even if the ticks remain
within the positive and negative noise thresholds the compensation procedure will then estimate new sets of
DCVs.
Finall y the h os t c an ini tia te a c ompensation procedure b y using the I2C int er f ac e ( in Acti ve or Do ze mode). This is
e.g. required after the host changed the sensitivity of sensors.
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3.9 Processing
The f irst pr ocessing st ep of the ra w tick s, com ing out of the ASI, is low p ass f iltering to o bta in an estim ation of the
average capacitance: tick-ave (see Figure 17).
This slowly varying average is important in the detection of slowly changing environmental changes.
ticks (raw)
compen sat io n DCV
ASI processing
low pass
tick-diff
tick-ave
processing
GPIO
controller
PWM LED
controller
I2C
SPM
Figure 17 Processing
The difference of the tick average and the raw ticks, tick-diff, is a good estimation of rapid changing input
capacitances.
The tic k - diff , tick-ave and the c onf ig ur ati on parameter s in t he SP M ar e th en proc ess ed an d d eter mines the sens or
information, I2C registers status and PWM control.
3.10 Configuration
Figure 18 shows the building blocks used for configuring the SX8649.
Figure 18 Configuration
The default configuration parameters of the SX8649 are stored in the Quick Start Memory (QSM). This
configuration data is setup to a very common application for the SX8649 with buttons and a wheel. Without any
programming or host interaction the SX8649 will startup in the Quick Start Application.
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The QSM settings are fixed and can not be changed by the user.
In case the application needs different settings than the QSM settings then the SX8649 can be setup and/or
programmed over the I2C interface.
The configuration parameters of the SX8649 can be stored in the Multiple Time Programmable (MTP) Non
Volatile Memory (NVM). The NVM contains all those parameters that are defined and stable for the application.
Examples are the number of sensors enabled, sensitivity, active and Doze scan period. The details of these
parameters are described in the next chapters.
At power up the SX8649 checks if the NVM contains valid data. In that case the configuration parameter source
becom es the NV M. If the NVM is em pt y or non- valid t h en the co nf iguration sourc e bec om es the QS M. In t he nex t
step the SX8649 copies the configur ation parameter source (QSM or N VM) into the Shadow Param eter Memory
(SPM). The SX8649 is operational and uses the configuration parameters of the SPM.
During p o wer do wn or r eset event th e SP M l oses a ll conte nt. I t will a utomatic all y be re loa ded ( f r om QSM or NVM)
following power up or at the end of the reset event.
The host will interface with the SX8649 through the I2C bus.
The I2C of the SX8649 consists of 16 registers. Some of these I2C registers are used to read the status and
information of the butto n an d the wheel. Other I2C r e gi s ters allo w the h os t to take contr ol of the SX 864 9. The host
can e.g. decide to change the operation mode from Active mode to Doze mode or go into Sleep (according to
Figure 8).
Two additional modes allow the host to have an access to the SPM or indirect access to the NVM.
These modes are required during development, can be used in real time or in-field programming.
Figure 19 shows the Host SPM mode. In this mode the host can decide to overwrite the SPM. This is useful
during the d ev elo pment phases of the applicati on wher e the conf igur at io n par ameters ar e not yet full y def ine d and
as well during the operation of the application if some parameters need to be changed dynamically.
Figure 19 Host SPM mode
The c ontent of the S PM re mains valid as lon g as the SX864 9 is po wer ed a nd no res et is perform ed. Af ter a po wer
down or reset the host needs to re-write the SPM if relevant for the application.
Figure 20 shows the Host NVM mode. In this mode the host will be able to write the NVM.
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Figure 20 Host NVM mode
The writing of the host towards the NVM is not done directly but done in 2 steps (Figure 20).
In the first step the host writes to the SPM (as in Figure 19). In the second step the host signals the SX8649 to
copy the SPM content into the NVM.
Initially the NVM memory is empty and it is required to determine a valid parameter set for the application. This
can be done during the development phase using dedicated evaluation hardware representing the final
application. This development phase uses probably initially the host SPM mode which allows faster iterations.
Once the p arameter set is determ ined this c an be writ ten to the NVM over the I2 C using the 2 steps appr oach by
the host or a dedicated programmer for large volumes production (as described in the paragraphs 6.6 and 6.7).
3.11 Power Management
The SX8649 uses on-chip voltage regulators which ar e controlled by the on-chip m icroprocessor. The regulators
need to be stabilized with an external capacitor between VANA and ground and between VDIG and ground (see
Table 5). Both regulators are designed to only drive the SX8649 internal circuitry and must not be loaded
externally.
3.12 Clock Circuitry
The SX8649 has its own internal clock generation circuitry that does not require any external components. The
clock circuitry is optimized for low power operation and is controlled by the on-chip microprocessor. The typical
operating frequency of the oscillating core is 16.7MHz from which all other lower frequencies are derived.
3.13 I2C interface
The I2C interface allows the communication between the host and the SX8649.
The I2C slave implemented on the SX8649 is compliant with the standard (100kb/s) and fast mode (400kb/s)
The default SX8649 I2C address equals 0b010 1011.
A different I2C address can be programmed by the user in the NVM.
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3.14 Reset
The reset can be performed by 3 sources:
- power up,
- RESETB pin,
- software reset.
3.14.1 Power up
During power up the INTB is kept low. Once the power up sequence is terminated the INTB is released
autonomously. The SX8649 is then ready for operation.
Figure 21 Power Up vs. INTB
During the po wer on p erio d the SX 8 649 s ta bi li zes th e i nternal reg ula tors , RC c loc k s and the f irmware in it ial i zes all
registers.
During the power up the SX8649 is not accessible and I2C communications are forbidden.
As soon as the INTB rises the SX8649 will be ready for I2C communication.
3.14.2 RESETB
When RESETB is driven low the SX8649 will reset and start the power up sequence as soon as RESETB is
driven high or pulled high.
In case the user does not require a hardware reset control pin then the RESETB pin can be connected to VDD.
Figure 22 Har dware Reset
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3.14.3 Software Reset
To perform a software reset the host needs to write 0xDE followed by 0x00 at the SoftReset register at address
0xB1.
Figure 23 Software Reset
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3.15 Interrupt
3.15.1 Power up
During power up the INTB is kept low. Once the power up sequence is terminated the INTB is released
autonomously. The SX8649 is then ready for operation.
Figure 24 Power Up vs. INTB
During the po wer on p erio d the SX 8 649 s ta bi li zes th e i nternal reg ula tors , RC c loc k s and the f irmware in it ial i zes all
registers.
During the power up the SX8649 is not accessible and I2C communications are forbidden.
As soon as the INTB rises the SX8649 will be ready for I2C communication.
3.15.2 Assertion
INTB is updated in Active or Doze mode once every scan period.
The INTB will be asserted: at the following events:
if a Button e vent oc curr ed (touch or r elease if enab led) . I2C regis ters Cap StatMs b and Ca pStatLs b sho w the
detailed status of the Buttons,
if a W heel event occ urr ed (touc h, r eleas e, r ot ate c lockwise, r otat e c ount er cloc k wis e or positi on c han ge) . I2 C
registers CapStatMsb, WhlPosMsb and WhlPosLsb show the detailed status of the Wheel,
if a GPI edge occur red (rising or f alling if enabled). I2C r egister Gpi Stat shows t he detailed stat us of the GPI
pins,
when actually entering Active or Doze mode either through automatic wakeup or via host request (may be
delayed by 1 scan period). I2C register CompOpmode shows the current operation mode,
once compensation procedure is completed either through automatic trigger or via host request (may be
delayed by 1 scan period),
once SPM write is effective (may be delayed by 1 scan period),
once NVM burn procedure is completed (may be delayed by 1 scan period),
during reset (power up, hardware RESETB, software reset).
3.15.3 Clearing
INTB is updated in Active or Doze mode once every scan period.
The clearing of the INTB is done as soon as the host performs a read to the IrqSrc I2C register or reset is
completed
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3.15.4 Example
A typical example of the assertion and clearing of the INTB and the I2C communication is shown in Figure 25.
Figure 25 Interrupt and I2C
When a button is touched the SX8649 will assert the interrupt (1). The host will read the IrqSrc information over
the I2C and this clears the interrupt (2).
If the f inger releas es the bu tton the inter ru pt will be as serted ( 3). The host r eading the IrqSr c inf orm ation will clear
the interrupt (4).
In case the host does not react to an interrupt this results in a missing touch.
3.16 General Purpose Input and Outputs
3.16.1 Introduction and Definitions
The SX 8649 of f er s eight Genera l P ur pose Inp ut a nd Outputs (G PIO) p ins whic h c an be c o nf igured in any of these
modes:
- GPI (General Purpose Input)
- GPP (General Purpose PWM)
- GPO (General Purpose Output)
Each of these modes is described in more details in the following sections.
The polarit y of the GPP and GPO pins is def ined as in figure below, dr iving an LED as exam ple. It has to be set
accordingly in SPM parameter GpioPolarity.
Figure 26 Polarit y definition, (a) norma l, (b) inverted
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The PWM blocks used in GPP and GPO modes are 8-bits based and clocked at 2MHz typ. hence offering 256
selectable pulse width values with a granularity of 128us typ.
Figure 27 PWM definition, (a) small pulse width, (b) large pulse width
3.16.2 GPI
GPIOs configured as GPI will operate as digital inputs with standard low and high logic levels.
Optional pull-up/down and debounce can be enabled. Each GPI is individually edge programmable for INTB
generation which will also exit Sleep/Doze mode if relevant.
SPM/I2C parameters applicable in GPI mode are listed in table below. Please refer to the relevant SPM/I2C
parameters sections for more details.
GPI
GpioMode X
GpioPullUpDown X
GpioInterrupt X
SPM
GpioDebounce X
IrqSrc[4] X
I2C GpiStat X
Table 7 SPM/I2C Parameters Applicable in GPI Mode
3.16.3 GPP
GPIOs configured as GPP will operate as PWM outputs directly controlled by the host. A typical application is
LED dimming.
Typical GPP operation is illustrated in figure below.
Figure 28 LED contro l in GPP mode
SPM/I2C parameters applicable in GPP mode are listed in table below. Please refer to the relevant SPM/I2C
parameters sections for more details.
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GPP
GpioMode X
GpioOutPwrUp X1
GpioPolarity X
GpioIntensityOn X1
GpioIntensityOff X1
SPM
GpioFunction X
GppPinId X
I2C GppIntensity X1
1 At power up, GppIntensit y of each GPP pin is initialized with GpioIntens ityOn or Gpi oInt ensityOff depending on GpioOutPwrUp
corresponding bits val ue.
Table 8 SPM/ I 2C Parameters Applicable in GPP Mode
3.16.4 GPO
GPIOs configured as GPO will operate as digital outputs which can generate both standard low/high logic levels
and PWM low/high duty cycles levels. Ty pical application is LED ON/OFF control.
Transitions between ON and OFF states can be triggered either automatically in Autolight mode or manually by
the host. This is illustrated in figures below.
Figure 29 LED Contr ol in GPO mode, Autolight OFF
Figure 30 LED Contr ol in GPO mode, Autolight ON (mapped to Button)
Addition ally these tra nsitions c an be conf igured to be done with or without f ading f ollowing a logarithmic or linear
function. This is illustrated in figures below.
Figure 31 GPO ON transition (LED fade in), normal polarity, (a) linear, (b) logarithmic
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Figure 32 GPO ON transition (L ED f ade in), inverted polarit y, (a) linear, (b) logarithmic
The fading o ut (e.g. af ter a button is releas ed) is identi cal to the f ading in bu t an addit ional of f dela y can be a dded
before the fading starts (Figure 33 and Figure 34).
Figure 33 GPO OFF transition ( L ED fade out), normal polarity, (a) linear, (b) logarit hmic
Figure 34 GPO OFF transition ( LED fade out), invert ed polarit y, (a) linear, (b) logarithmic
Please n ote tha t stan dard hig h/lo w log ic sig nals ar e ju st a spec ific case of GPO m ode and can also b e ge nerated
simply by setting inc/dec time to 0 (ie OFF) and programming intensity OFF/ON to 0x00 and 0xFF.
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SPM/I2C parameters applicable in GPO mode are listed in table below.
GPO
GpioMode X
GpioOutPwrUp X1
GpioAutoligth X
GpioPolarity X
GpioIntensityOn X
GpioIntensityOff X
GpioFunction X
GpioIncFactor X
GpioDecFactor X
GpioIncTime X
GpioDecTime X
SPM
GpioOffDelay X
I2C GpoCtrl X2
1 Only if Autolight is OFF, else must be left to 0 (default value)
2 Only if Autolight is OFF, else ignored
Table 9 SPM/I2C Parameters Applicable in GPO Mode
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3.16.5 Intensity index vs PWM pulse width
Tables below are used to convert all intensity indexes parameters GpioIntensityOff, GpioIntensityOn and
GppIntensity but also to generate fading in GPO mode
During fading in(out), the index is automatically incremented(decremented) at every Inc(Dec)Time x
Inc(Dec)Factor until it reaches the programmed GpioIntensityOn(Off) value.
Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log
0 0/0 32 33/5 64 65/12 96 97/26 128 129/48 160 161/81 192 193/125 224 225/184
1 2/0 33 34/5 65 66/13 97 98/27 129 130/49 161 162/82 193 194/127 225 226/186
2 3/0 34 35/5 66 67/13 98 99/27 130 131/50 162 163/83 194 195/129 226 227/188
3 4/0 35 36/5 67 68/13 99 100/28 131 132/51 163 164/84 195 196/130 227 228/190
4 5/0 36 37/5 68 69/14 100 101/29 132 133/52 164 165/86 196 197/132 228 229/192
5 6/2 37 38/6 69 70/14 101 102/29 133 134/53 165 166/87 197 198/133 229 230/194
6 7/2 38 39/6 70 71/14 102 103/30 134 135/54 166 167/88 198 199/135 230 231/197
7 8/2 39 40/6 71 72/15 103 104/30 135 136/55 167 168/89 199 200/137 231 232/199
8 9/2 40 41/6 72 73/15 104 105/31 136 137/55 168 169/91 200 201/139 232 233/201
9 10/2 41 42/6 73 74/15 105 106/32 137 138/56 169 170/92 201 202/140 233 234/203
10 11/2 42 43/7 74 75/16 106 107/32 138 139/57 170 171/93 202 203/142 234 235/205
11 12/2 43 44/7 75 76/16 107 108/33 139 140/58 171 172/95 203 204/144 235 236/208
12 13/2 44 45/7 76 77/16 108 109/33 140 141/59 172 173/96 204 205/146 236 237/210
13 14/2 45 46/7 77 78/17 109 110/34 141 142/60 173 174/97 205 206/147 237 238/212
14 15/3 46 47/7 78 79/17 110 111/35 142 143/61 174 175/99 206 207/149 238 239/215
15 16/3 47 48/8 79 80/18 111 112/35 143 144/62 175 176/100 207 208/151 239 240/217
16 17/3 48 49/8 80 81/18 112 113/36 144 145/63 176 177/101 208 209/153 240 241/219
17 18/3 49 50/8 81 82/19 113 114/37 145 146/64 177 178/103 209 210/155 241 242/221
18 19/3 50 51/8 82 83/19 114 115/38 146 147/65 178 179/104 210 211/156 242 243/224
19 20/3 51 52/9 83 84/20 115 116/38 147 148/66 179 180/106 211 212/158 243 244/226
20 21/3 52 53/9 84 85/20 116 117/39 148 149/67 180 181/107 212 213/160 244 245/229
21 22/3 53 54/9 85 86/21 117 118/40 149 150/68 181 182/109 213 214/162 245 246/231
22 23/3 54 55/9 86 87/21 118 119/40 150 151/69 182 183/110 214 215/164 246 247/233
23 24/4 55 56/10 87 88/22 119 120/41 151 152/71 183 184/111 215 216/166 247 248/236
24 25/4 56 57/10 88 89/22 120 121/42 152 153/72 184 185/113 216 217/168 248 249/238
25 26/4 57 58/10 89 90/23 121 122/43 153 154/73 185 186/114 217 218/170 249 250/241
26 27/4 58 59/10 90 91/23 122 123/44 154 155/74 186 187/116 218 219/172 250 251/243
27 28/4 59 60/11 91 92/24 123 124/44 155 156/75 187 188/117 219 220/174 251 252/246
28 29/4 60 61/11 92 93/24 124 125/45 156 157/76 188 189/119 220 221/176 252 253/248
29 30/4 61 62/11 93 94/25 125 126/46 157 158/77 189 190/121 221 222/178 253 254/251
30 31/4 62 63/12 94 95/25 126 127/47 158 159/78 190 191/122 222 223/180 254 255/253
31 32/5 63 64/12 95 96/26 127 128/48 159 160/80 191 192/124 223 224/182 255 256/256
Table 10 Intensity index vs. PWM pulse widt h (normal polar ity)
Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log
0 256/256 32 224/251 64 192/244 96 160/230 128 128/208 160 96/175 192 64/131 224 32/72
1 255/256 33 223/251 65 191/243 97 159/229 129 127/207 161 95/174 193 63/129 225 31/70
2 254/256 34 222/251 66 190/243 98 158/229 130 126/206 162 94/173 194 62/127 226 30/68
3 253/256 35 221/251 67 189/243 99 157/228 131 125/205 163 93/172 195 61/126 227 29/66
4 252/256 36 220/251 68 188/242 100 156/227 132 124/204 164 92/170 196 60/124 228 28/64
5 251/254 37 219/250 69 187/242 101 155/227 133 123/203 165 91/169 197 59/123 229 27/62
6 250/254 38 218/250 70 186/242 102 154/226 134 122/202 166 90/168 198 58/121 230 26/59
7 249/254 39 217/250 71 185/241 103 153/226 135 121/201 167 89/167 199 57/119 231 25/57
8 248/254 40 216/250 72 184/241 104 152/225 136 120/201 168 88/165 200 56/117 232 24/55
9 247/254 41 215/250 73 183/241 105 151/224 137 119/200 169 87/164 201 55/116 233 23/53
10 246/254 42 214/249 74 182/240 106 150/224 138 118/199 170 86/163 202 54/114 234 22/50
11 245/254 43 213/249 75 181/240 107 149/223 139 117/198 171 85/161 203 53/112 235 21/48
12 244/254 44 212/249 76 180/240 108 148/223 140 116/197 172 84/160 204 52/110 236 20/46
13 243/254 45 211/249 77 179/239 109 147/222 141 115/196 173 83/159 205 51/109 237 19/44
14 242/253 46 210/249 78 178/239 110 146/221 142 114/195 174 82/157 206 50/107 238 18/41
15 241/253 47 209/248 79 177/238 111 145/221 143 113/194 175 81/156 207 49/105 239 17/39
16 240/253 48 208/248 80 176/238 112 144/220 144 112/193 176 80/155 208 48/103 240 16/37
17 239/253 49 207/248 81 175/237 113 143/219 145 111/192 177 79/153 209 47/101 241 15/35
18 238/253 50 206/248 82 174/237 114 142/218 146 110/191 178 78/152 210 46/100 242 14/32
19 237/253 51 205/247 83 173/236 115 141/218 147 109/190 179 77/150 211 45/98 243 13/30
20 236/253 52 204/247 84 172/236 116 140/217 148 108/189 180 76/149 212 44/96 244 12/27
21 235/253 53 203/247 85 171/235 117 139/216 149 107/188 181 75/147 213 43/94 245 11/25
22 234/253 54 202/247 86 170/235 118 138/216 150 106/187 182 74/146 214 42/92 246 10/23
23 233/252 55 201/246 87 169/234 119 137/215 151 105/185 183 73/145 215 41/90 247 9/20
24 232/252 56 200/246 88 168/234 120 136/214 152 104/184 184 72/143 216 40/88 248 8/18
25 231/252 57 199/246 89 167/233 121 135/213 153 103/183 185 71/142 217 39/86 249 7/15
26 230/252 58 198/246 90 166/233 122 134/212 154 102/182 186 70/140 218 38/84 250 6/13
27 229/252 59 197/245 91 165/232 123 133/212 155 101/181 187 69/139 219 37/82 251 5/10
28 228/252 60 196/245 92 164/232 124 132/211 156 100/180 188 68/137 220 36/80 252 4/8
29 227/252 61 195/245 93 163/231 125 131/210 157 99/179 189 67/135 221 35/78 253 3/5
30 226/252 62 194/244 94 162/231 126 130/209 158 98/178 190 66/134 222 34/76 254 2/3
31 225/251 63 193/244 95 161/230 127 129/208 159 97/176 191 65/132 223 33/74 255 0/0
Table 11 I nt ensity index vs. PWM pulse width (inverted polarity)
Recommended/default settings are inverted polarity (to take advantage from high sink current capability) and
logarithmic mode (due to the non-linear response of the human eye).
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3.17 Smart Wake Up
The SX8649 offers a smart wake up mechanism which allows waking-up from the Doze low power mode to the
Active mode in a secure/controlled way and not by any unintentional sensor activation.
Until the f ull correct wake-up seque nce is entere d, the SX864 9 will rem ain in Doze m ode. Any wron g key implies
the whole sequence to be entered again.
A sequence of up to 6 keys can be defined. Each key must be followed by a release to be validated.
The smart wake-up mechanism can also be disabled which implies that Doze mode can hence only be exited
from GPI or I2C command.
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4 PIN DESCRIPTIONS
4.1 Introduction
This chapter describes briefly the pins of the SX8649, the way the pins are protected, if the pins are analog,
digital, require pull up or pull down resistors and show control signals if these are available.
4.2 ASI pins
CAP0, CAP1, ..., CAP7
The capacitance sensor pins (CAP0, CAP1, ..., CAP7) are connected directly to the ASI circuitry which converts
the sensed capacitance into digital values.
The capacitance sensor pins which are not used should be left open.
The enabled CAP pins need be connected directly to the sensors without significant resistance (typical below
some ohms, connection vias are allowed).
The capacitance sensor pins are protected to VANA and GROUND.
Figure 35 shows the simplified diagram of the CAP0, CAP1, ..., CAP7 pins.
SX8649
sensor ASI CAPx CAP_INx
VANA
Note : x = 0, 1,2,…7
Figure 35 Simplif ied diagr am of CAP0, CAP1, ..., CAP7
CN, CP
The CN and the C P pins ar e connecte d to the AS I circ uitry. A 1nF s am pling c apacitor between C P and CN n eeds
to be placed as close as possible to the SX8649.
The CN and CP are protected to VANA and GROUND.
Figure 36 shows the simplified diagram of the CN and CP pins.
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SX8649
ASI
CP
VANA
CN
VANA
Figure 36 Simplified diagram of CN and CP
4.3 Host interface pins
The host interface consists of the interrupt pin INTB, a reset pin RESETB and the standard I2C pins: SCL and
SDA.
INTB
The INTB pin is an open drain output that requires an external pull-up resistor (1..10 kOhm). The INTB pin is
protected to VDD using dedicated devices. The INTB pin has diode protected to GROUND.
Figure 37 shows a simplified diagram of the INTB pin.
VDD
R_INT
INTB
SX8649
INT
to host
Figure 37 Simplified diagram of INTB
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SCL
The SCL pi n is a h igh impedance in put pin. The SCL pin is pr o tec ted to V DD, using dedic a ted de v ice s, i n or d er to
conform to standard I2C slave specifications. The SCL pin has diode protected to GROUND.
An external pull-up resistor (1..10 kOhm) is required on this pin.
Figure 38 shows the simplified diagram of the SCL pin.
VDD
R_SCL
SCL
SX8649
from host
SCL_IN
Figure 38 Simplified diagram of SCL
SDA
SDA is an IO pin that can be used as an open drain output pin with external pull-up resistor or as a high
impedance input pin. The SDA IO pin is protected to VDD, using dedicated devices, in order to conform to
standard I2C slave specifications. The SDA pin has diode protected to GROUND.
An external pull-up resistor (1..10 kOhm) is required on this pin.
Figure 39 shows the simplified diagram of the SDA pin.
VDD
R_SDA
SDA
SX8649
SDA_OUT
from/to host
SDA_IN
Figure 39 Simplified diagram of SDA
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RESETB
The RESETB pin is a high impedance input pin. The RESETB pin is protected to VDD using dedicated devices.
The RESETB pin has diode protected to GROUND.
Figure 40 shows the simplified diagram of the RESETB pin controlled by the host.
VDD
R_RESETB
RESETB
SX8649
from host
RESETB_IN
Figure 40 Simplified diagr am of RESETB controlled by host
Figure 41 shows the RESETB without host control.
VDD
RESETB
SX8649
RESETB_IN
Figure 41 Simplified diagr am of RESETB without host control
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4.4 Power management pins
The power management pins consist of the Power, Ground and Regulator pins.
VDD
VDD is a power pin and is the main power supply for the SX8649.
VDD has protection to GROUND.
Figure 42 shows a simplified diagram of the VDD pin.
VDD
SX8649
VDD
Figure 42 Simplified diagram of VDD
GND
The SX 8649 has four grou nd pins al l nam ed GND. T hese pins and th e pack age center pad ne ed to be c onnected
to ground potential.
The GND has protection to VDD.
Figure 43 shows a simplified diagram of the GND pin.
VDD
SX8649
GND GND
Figure 43 Simplified diagram of GND
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VANA, VDIG
The SX8649 has on-chip regulators for internal use (pins VANA and VDIG).
VANA and VDIG have protection to VDD and to GND.
The output of the regulators needs to be de-coupled with a small 100nF capacitor to ground.
Figure 44 shows a simplified diagram of the VANA and VDIG pin.
VDD
SX8649
GND
VDIG
VDD
GND
VANA
VANA
VDIG
Cvdig
Cvana
Figure 44 Simplified diagram of VANA and VDIG
4.5 General purpose IO pins
The SX8649 has 8 General purpose input/output (GPIO) pins.
All the GPIO pins have protection to VDD and GND.
The GPIO pins can be configured as GPI, GPO or GPP.
Figure 45 shows a simplified diagram of the GPIO pins.
Figure 45 Simplified diagram of GPIO pins
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5 DETAILED CONFIGURATION DESCRIPTIONS
5.1 Introduction
The SX 8649 configur ati on parameter s ar e taken from the QSM or the N VM and l oade d i nto th e SPM as ex p l ain ed
in the chapter ‘functional description’.
This chapter describes the details of the configuration parameters of the SX8649.
.
The SPM is split by functionality into 6 configuration sections:
General section: operating modes,
Capacitive Sensors section: related to lower level capacitive sensing,
Button: related to the conversion from sensor data towards button information,
Wheel: related to the conversion from sensor data towards wheel information,
Mapping: related to mapping of button and wheel information towards wake-up and GPIO pins,
GPIO: related to the setup of the GPIO pins.
The total address space of the SPM and the NVM is 128 bytes, from address 0x00 to address 0x7F.
Two types of memory addresses, data are accessible to the user.
‘application data’: Application dependent data that need to be configured by the user.
‘reserved’: Data that need to be maintained by the user to the QSM default values (i.e. when NVM is burned).
The Table 12 and Table 13 resume the complete SPM address space and show the ‘application data’ and
‘reserved’ addresses, the functional split and the default values (loaded from the QSM).
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Address Name default QSM
value Address Name default QSM
value
0x00 Reserved 0xxx 0x20 Reserved 0x00
0x01 Reserved 0xxx 0x21 BtnCfg 0x30
0x02 Reserved 0x38 0x22 BtnAvgThresh 0x50
0x03 Reserved 0xxx 0x23 BtnCompNegThresh 0x50
0x04 I2CAddress 0x2B 0x24 BtnCompNegCntMax 0x01
0x05 ActiveScanPeriod 0x02 0x25 BtnHysteresis 0x0A
0x06 DozeScanPeriod 0x0D 0x26
Button
BtnStuckAtTimeout 0x00
0x07
General
PassiveTimer 0x00 0x27 WhlCfg 0x00
0x08 Reserved 0x00 0x28 WhlStuckAtTimeout 0x00
0x09 CapModeMisc 0x01 0x29 WhlHysteresis 0x03
0x0A Reserved 0x00 0x2A Reserved 0xFF
0x0B CapMode7_4 0xFF 0x2B WhlNormMsb 0x02
0x0C CapMode3_0 0x55 0x2C WhlNormLsb 0x00
0x0D CapSensitivity0_1 0x00 0x2D WhlAvgThresh 0x50
0x0E CapSensitivity2_3 0x00 0x2E WhlCompNegThresh 0x50
0x0F CapSensitivity4_5 0x00 0x2F WhlCompNegCntMax 0x01
0x10 CapSensitivity6_7 0x00 0x30 WhlRotateThresh 0x02
0x11 Reserved 0x00 0x31
Wheel
WhlOffset 0x00
0x12 Reserved 0x00 0x32
Reserved 0x00
0x13 CapThresh0 0xA0 0x33 MapWakeupSize 0x00
0x14 CapThresh1 0xA0 0x34 MapWakeupValue0 0x00
0x15 CapThresh2 0xA0 0x35 MapWakeupValue1 0x00
0x16 CapThresh3 0xA0 0x36 MapWakeupValue2 0x00
0x17 CapThresh4 0xA0 0x37 MapAutoLight0 0xCC
0x18 CapThresh5 0xA0 0x38 MapAutoLight1 0xCC
0x19 CapThresh6 0xA0 0x39 MapAutoLight2 0x32
0x1A CapThresh7 0xA0 0x3A MapAutoLight3 0x10
0x1B Reserved 0xA0 0x3B MapAutoLightGrp0Msb 0x40
0x1C Reserved 0xA0 0x3C MapAutoLightGrp0Lsb 0x00
0x1D Reserved 0xA0 0x3D MapAutoLightGrp1Msb 0x00
0x1E Reserved 0xA0 0x3E MapAutoLightGrp1Lsb 0x00
0x1F
Capacitive Sensors
CapPerComp 0x00 0x3F
Mapping
MapSegmentHysteresis 0x02
Table 12 SPM address map: 0x00…0x3F
Note
‘0xxx’: write p rotected data
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Address Name default QSM
value Address Name default QSM
value
0x40 GpioMode7_4 0x00 0x60 GpioDecTime1_0 0x44
0x41 GpioMode3_0 0x00 0x61 GpioOffDelay7_6 0x00
0x42 GpioOutPwrUp 0x00 0x62 GpioOffDelay5_4 0x00
0x43 GpioAutoLight 0xFF 0x63 GpioOffDelay3_2 0x00
0x44 GpioPolarity 0x00 0x64 GpioOffDelay1_0 0x00
0x45 GpioIntensityOn0 0xFF 0x65 GpioPullUpDown7_4 0x00
0x46 GpioIntensityOn1 0xFF 0x66 GpioPullUpDown3_0 0x00
0x47 GpioIntensityOn2 0xFF 0x67 GpioInterrupt7_4 0x00
0x48 GpioIntensityOn3 0xFF 0x68 GpioInterrupt3_0 0x00
0x49 GpioIntensityOn4 0xFF 0x69
Gpio
GpioDebounce 0x00
0x4A GpioIntensityOn5 0xFF 0x6A
Reserved 0x00
0x4B GpioIntensityOn6 0xFF 0x6B Reserved 0x00
0x4C GpioIntensityOn7 0xFF 0x6C Reserved 0x00
0x4D GpioIntensityOff0 0x00 0x6D Reserved 0x00
0x4E GpioIntensityOff1 0x00 0x6E Reserved 0x00
0x4F GpioIntensityOff2 0x00 0x6F Reserved 0x50
0x50 GpioIntensityOff3 0x00 0x70 Reserved 0x46
0x51 GpioIntensityOff4 0x00 0x71
Reserved 0x10
0x52 GpioIntensityOff5 0x00 0x72 Reserved 0x45
0x53 GpioIntensityOff6 0x00 0x73 Reserved 0x02
0x54 GpioIntensityOff7 0x00 0x74 Reserved 0xFF
0x55 Reserved 0xFF 0x75 Reserved 0xFF
0x56 GpioFunction 0x00 0x76 Reserved 0xFF
0x57 GpioIncFactor 0x00 0x77 Reserved 0xD5
0x58 GpioDecFactor 0x00 0x78 Reserved 0x55
0x59 GpioIncTime7_6 0x00 0x79 Reserved 0x55
0x5A GpioIncTime5_4 0x00 0x7A Reserved 0x7F
0x5B GpioIncTime3_2 0x00 0x7B Reserved 0x23
0x5C GpioIncTime1_0 0x00 0x7C Reserved 0x22
0x5D GpioDecTime7_6 0x44 0x7D Reserved 0x41
0x5E GpioDecTime5_4 0x44 0x7E Reserved 0xFF
0x5F
Gpio
GpioDecTime3_2 0x44 0x7F
SpmCrc* 0xC3
Table 13 SPM address map: 0x40…0x7F
Note*
SpmCrc: CRC depending on SPM content, updated in Active or Doze mode.
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5.2 General Parameters
General Parameters
Address Name Bits Description
7 Reserved 0x04 I2CAddress
6:0 Defines the I2C address (default 0x2B).
The I2C address will be active after a reset.
0x05 ActiveScanPeriod 7:0 Active Mode Scan Period (Figure 7)
0x00: Reserved
0x01: 15ms
0x02: 30ms (default)
0xFF: 255 x 15ms
0x06 DozeScanPeriod 7:0 Doze Mode Scan Period (Figure 7)
0x00: Reserved
0x01: 15ms
0x0D: 195ms (default)
0xFF: 255 x 15ms
0x07 PassiveTimer 7:0 Passive Timer on Button and Wheel Information (Figure 8)
0x00: OFF (default)
0x01: 1 second
0xFF: 255 seconds
Table 14 G ener al Par a m eter s
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5.3 Capacitive Sensors Parameters
Capacitive Sensors Parameters
Address Name Bits Description
7:3 Reserved
2 IndividualSensitivity Defines common sensitivity for all sensors or individual
sensor sensitiv ity .
0: Common settings (CapSensitivity0_1[7:4])
1: Individual CAP sensitivity settings (CapSensitivityx_x)
0x09 CapModeMisc
1:0 Reserved Reserved: ‘01’
0x0A Reserved 7:0 Reserved
7:6 CAP7 Mode Wheel
5:4 CAP6 Mode Wheel
3:2 CAP5 Mode Wheel
0x0B CapMode7_4
1:0 CAP4 Mode Wheel
7:6 CAP3 Mode Button
5:4 CAP2 Mode Button
3:2 CAP1 Mode Button
0x0C CapMode3_0
1:0 CAP0 Mode
Defines the mode of
the CAP pin.
00: Disabled
01: Button
10: Reserved
11: Wheel
Default
Button
7:4 CAP0 Sensitivity - Common Sensitivity 0x0D CapSensitivity0_1
3:0 CAP1 Sensitivity
7:4 CAP2 Sensitivity 0x0E CapSensitivity2_3
3:0 CAP3 Sensitivity
7:4 CAP4 Sensitivity 0x0F CapSensitivity4_5
3:0 CAP5 Sensitivity
7:4 CAP6 Sensitivity 0x10 CapSensitivity6_7
3:0 CAP7 Sensitivity
Defines the sensitivity.
0x0: Minimum (default)
0x7: Maximum
0x8…0xF: Reserved
0x11 Reserved 7:0 Reserved
0x12 Reserved 7:0 Reserved
0x13 CapThresh0 7:0 CAP0 Touch Threshold
0x14 CapThresh1 7:0 CAP1 Touch Threshold
0x15 CapThresh2 7:0 CAP2 Touch Threshold
0x16 CapThresh3 7:0 CAP3 Touch Threshold
0x17 CapThresh4 7:0 CAP4 Touch Threshold
0x18 CapThresh5 7:0 CAP5 Touch Threshold
0x19 CapThresh6 7:0 CAP6 Touch Threshold
0x1A CapThresh7 7:0 CAP7 Touch Threshold
Defines the Touch Threshold ticks.
0x00: 0,
0x01: 4,
0xA0: 640 (default),
0xFF: 1020
0x1B Reserved 7:0 Reserved
0x1C Reserved 7:0 Reserved
0x1D Reserved 7:0 Reserved
0x1E Reserved 7:0 Reserved
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Capacitive Sensors Parameters
Address Name Bits Description
7:4 Reserved 0x1F CapPerComp
3:0 Periodic Offset Compensation Defines the periodic offset compensation.
0x0: OFF (default)
0x1: 1 second
0x2: 2 seconds
0x7: 7 seconds
0x8: 16 seconds
0x9: 18 seconds
0xE: 28 seconds
0xF: 60 seconds
Table 15 Capacitive Sensors Parameters
CapModeMisc
By default th e A SI is using a c om m on s ens itiv ity for all c apac iti ve sens or s as in t h e us ual c as e o verl a y m ateri al
and sensors sizes are about equal. The register bits CapSensitivity0_1[7:4] determine the sensitivity for all
sensors in common sensitivity mode.
In specia l appl ications it m ight be re quired to h ave a d iff erent, indi vidual, s ens itivit y for each C AP pin. T his c an
be obtained by setting bit CapModeMisc[2]. The individual sensitivity mode results in longer sensing periods
than required in common sensitivity mode.
CapMode7_4, CapMode3_0:
The CAP pins can be set as a button, part of a wheel or disabled depending on the application.
minimum default maximum
buttons one four four
wheel one
(of four sensors) one
(of four sensors) one
(of six sensors)
Table 16 Possible CAP pin modes
Buttons and disabled CAP pins can be attributed freely (examples in Figure 46).
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Figure 46 Button examples
Disabled CAP pins inside the wheel sensor attribution sequence are allowed, but CAP buttons inside a wheel
are not allowed (see example Figure 47 with CAP3 in a correct and a not allowed configuration).
Figure 47 Button and Wheel good/bad configuration examples (I)
The physical order of the wheel sensors on the PCB should correspond to the incremental CAP pin numbers.
Crossing wheel PCB sensors and CAP number is not allowed. Figure 48 shows a valid configuration and a
wrong configuration where CAP5 andCAP6 are not routed correctly on the PCB.
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Figure 48 Button and Wheel good/bad configuration examples (II)
The m inimum pos ition of th e wheel is ass ociated to th e CAP pin, at tributed t o the whee l, with th e lowest ind ex
(in Figure 48 this is CAP2).
The maximum position of the wheel is associated to the CAP pin, attributed to the wheel, with the highest
index (in Figure 48 this is CAP6).
CapSensitivity0_1, CapSensitivity2_3, CapSensitivity4_5, CapSensitivity6_7:
The s ensitiv ity of the s ensor s can be s et bet wee n 8 va l ues. The higher th e s ens it iv it y is set the lar g er the val u e
of the ticks will be.
The minimum sensitivity can be used for thin overlay materials and large sensors, while the maximum
sensitivity is required for thicker overlay and smaller sensors.
The required sensitivity needs to be determined during a product development phase. Too low sensitivity
settings result in missing touches. Too high sensitivity settings will result in fault detection of fingers hovering
above the sensors.
The s ensitivit y is ident ical f or all sens ors in com m on sensit ivity m ode using the bi ts CapS ensit ivit y0_1[7:4] a nd
can be set individually using register CapModeMisc[2].
The m aximum num ber of ticks that can be obtain ed depends on the selecte d sensiti vity as illustr ated in T able
17.
Sensitivity Approximate
Maximum Tick Level
0 1000
1 2000
2 3000
3 4000
4 5000
5 6000
6 7000
7 8000
Table 17 ASI Maximum Tick Levels
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CapThresh0, CapThresh1, CapThresh2, CapThresh3, CapThresh4, CapThresh5, CapThresh6, CapThresh7:
For each CAP pin a threshold level can be set individually.
The threshold levels are used by the SX8649 for making touch and release decisions on e.g. touch or no-
touch.
The details are explained in the sections for buttons and wheel.
CapPerComp:
The SX8649 offers a periodic offset compensation for applications which are subject to substantial
environmental changes. The periodic offset compensation is done at a defined interval and only if wheel and
buttons are released.
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5.4 Button Parameters
Button Parameters
Address Name Bits Description
7:6 Defines the buttons events reporting method.
00: Multiple reporting of all touches and releases (default)
01: Single reporting of the first button touch. Next button touches and releases are
ignored until release of the first button.
10: Reserved
11: Reserved
5:4 Defines the buttons interrupt (for all buttons)
00 : Interrupts masked
01 : Triggered on Touch
10 : Triggered on Release
11 : Triggered on Touch and Release (default)
3:2 Defines the number of samples at the scan period for determining a release
00: OFF, use incoming sa mpl e (default)
01: 2 samples debounce
10: 3 samples debounce
11: 4 samples debounce
0x21 BtnCfg
1:0 Defines the number of samples at the scan period for determining a touch
00: OFF, use incoming sa mpl e (default)
01: 2 samples debounce
10: 3 samples debounce
11: 4 samples debounce
0x22 BtnAvgThresh 7:0 Defines the positive threshold for disabling the processing filter averaging.
If ticks are above the threshold, then the averaging is suspended
0x00: 0
0x01: 4
0x50: 320 (default)
0xFF: 1020
0x23 BtnCompNegThresh 7:0 Defines the negative offs et co mpen sation threshold.
0x00: 0
0x01: 4
0x50: 320 (default)
0xFF: 1020
0x24 BtnCompNegCntMax 7:0 Defines the number of ticks (below the negative offset compensation threshold)
which will initiate an offset compensation.
0x00: Reserved
0x01: 1 sample (default)
0xFF-> samples
0x25 BtnHysteresis 7:0 Defines the button hysteresis corresponding to a percentage of the CAP thresholds
(defined in Table 18).
0x00: 0%
0x0A: 10% (default)
0x64: 100%
All buttons use the same hysteresis
0x26 BtnStuckAtTimeout 7:0 Defines the stuck at timeout.
0x00: OFF (default)
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Button Parameters
Address Name Bits Description
0x01: 1 second
0xFF: 255 seconds
Table 18 Button Conf iguration Paramet ers
A reliable button operation requires a coherent setting of the registers.
Figure 49 shows an example of a touch and a release. The ticks will vary slightly around the zero idle state.
When the touch occurs the ticks will rise sharply. At the release of the button the ticks will go down rapidly and
converge to the idle zero value.
ticks_diff
Figure 49 Touch and Release Example
As soon as the ticks become larger than the CAP thresholds (see registers of the previous section) plus the
hysteresis (defined in register BtnHysteresis) the debounce counter starts.
In the example of Figure 49 the touch is validated after 2 samples (BtnCfg [1:0] = 01).
The releas e is d etecte d im m ediatel y (BtnCfg [3:2] = 00) at the firs t sam ple which is bel ow the thr esh old m inus the
hysteresis.
BtnCfg
The SX 8649 can r e por t a ll t ouc hes of m ultiple finger s o r the SX 86 49 c an be set to r epor t on ly the f ir st det ec te d
touch. In the later case all succeeding touches are ignored. The very first touch should be released before a
next touch will be detected.
The user can select to have the interrupt signal on touching a button, releasing a button or both
In noisy environments it may be required to debounce the touch and release detection decision.
In case the debounce is enabled the SX8649 will count up to the number of debounce samples BtnCfg [1:0],
BtnCfg [3:2] before taking a touch or release decision. The sample period is identical to the scan period.
BtnAvgThresh
Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value.
In case the ticks get slightly positive this is considered as normal operation. Very large positive tick values
indicate a valid touch. The averaging filter is disabled as soon as the average reaches the value defined by
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Touch Controller (8 sensors) with Enhanced LED Drivers
BtnAvgThresh. This mechanism avoids that a valid touch will be averaged and finally the tick difference
becomes zero.
In case three or more sensors reach the BtnAvgThresh value simultaneously then the SX8649 will start an
offset compensation procedure.
Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value.
In case the ticks get slightly negative this is considered as normal operation. However large negative values will
trigger an offset compensation phase and a new set of DCVs will be obtained.
The decision to trigger a compensation phase based on negative ticks is determined by the value in the register
BtnCompNegThresh and by the number of ticks below the negative thresholds defined in register
BtnCompNegCntMax. An example is shown in Figure 50.
ticks_diff
Figure 50 Negative Ticks Offset Compensation Trigger
BtnCompNegThresh
Small negative ticks are considered as normal operation and will occur very often.
Larger negative ticks however need to be avoided and a convenient method is to trigger an offset
compensation phase. The new set of DCV will assure the idle ticks will be close to zero again.
A trade-off has to be found for the value of this register. A negative threshold too close to zero will trigger a
compensation phase very often. A very negative threshold will never trigger.
BtnCompNegCntMax
As soon as the ticks get smaller than the Negative Threshold the Negative Counter starts to count.
If the counter goes beyond the Negative Counter Max then the offset compensation phase is triggered.
The re comm ended va lue f or this r egister is ‘1 ’ which m eans that th e off set c ompens ation s tarts on the fir st tick
below the negative threshold.
BtnHysteresis
The hysteresis percentage is identical for all buttons.
A touch is detected if the ticks are getting larger as the value defined by:
CapThreshold + CapThreshold * hysteresis.
A release is detected if the ticks are getting smaller as the value defined by:
CapThreshold - CapThreshold * hysteresis.
BtnStuckAtTimeout
The stuckat timer can avoid sticky buttons.
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If the stuc kat timer is set to one sec ond then th e touch of a f inger will las t only for one second an d consid ered
released, even if the finger remains on the button for a longer time. After the actual finger release the button
can be touched again and will be reported as usual.
In case the stuckat timer is not required it can be set to zero.
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5.5 Wheel Parameters
Wheel Parameters
Address Name Bits Description
7:4 Reserved
3:2 Defines the number of samples at the scan period for determining a release
00: OFF, use incoming sa mpl e (default)
01: 2 samples debounce
10: 3 samples debounce
11: 4 samples debounce
0x27 WhlCfg
1:0 Defines the number of samples at the scan period for determining a touch
00: OFF, use incoming sa mpl e (default)
01: 2 samples debounce
10: 3 samples debounce
11: 4 samples debounce
0x28 WhlStuckAtTimeout 7:0 Defines the stuck at timeout.
0x00: OFF (default)
0x01: 1 second
0xFF: 255 seconds
0x29 WhlHysteresis 7:0 Defines the Wheel Touch/Release Hysteresis.
0x00: 0
0x01: 4
0x03: 12 (default)
0xFF: 1020
0x2B WhlNormMsb 7:0 Wheel Norm Msb
0x2C WhlNormLsb 7:0 Wheel Norm Lsb
Defines the 16 bits wheel norm (default 0x0200)
0x2D WhlAvgThresh 7:0 Defines the positive threshold for disabling the processing filter averaging.
If ticks are above the threshold, then the averaging is suspended
0x00: 0
0x01: 4
0x50: 320 (default)
0xFF: 1020
0x2E WhlC om pNegT hres h 7:0 Defines the negative offset co mpen sation threshold.
0x00: 0
0x01: 4
0x50: 320 (default)
0xFF: 1020
0x2F WhlCompNegCntMax 7:0 Defines the number of ticks (below the negative offset compensation threshold)
which will initiate an offset compensation.
0x00: Reserved
0x01: 1 sample (default)
0xFF: 255 samples
0x30 WhlRotateThresh 7:0 Defines the threshold for detecting a rotate clockwise or counter clockwise.
The threshold is a percentage of the maximum wheel position.
0x00: 0%
0x02: 2% (default)
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Wheel Parameters
Address Name Bits Description
0x64: 100%
A succeeding position difference, at the scan period, above the threshold is
considered as a rotate clockwise or counter clockwise.
0x31 WhlOffset 7:0 Defines the angle (offset /256 * 360 degree) added to the wheel position in
clockw ise dir e ctio n.
0x00: 0 (default)
0x01: 1/256
0xFF: 255/256
Table 19 Wheel Param eters
A reliable wheel operation requires a coherent setting of the registers.
The pressure represents the finger touch on the sensors of the wheel and it used to determine if a wheel is
touched or released.
=
=
1
0))()(_(
N
iiCapThreshidifftickseWhlPressur
- N is the number of sensors,
- A sensor with ticks smaller than the CapThreshold is not taken into account for calculating the pressure
In case the pressure equals zero the wheel status is released.
In case the pressure is larger as the Wheel Hysteresis the wheel status is touched.
Figure 51 shows an example of a touch and a release. The ticks will vary slightly around the zero idle state.
When the touch occurs the ticks will rise sharply. At the release of the wheel the ticks will go down rapidly and
converge to the idle zero value.
time
0
WhlHysteresis
= no-touch
Touch
(touch debounce = 1)
= touch
(release debounce = 0)
Release
CapThreshold
= scan events @ scan period
WhlHysteresis
Touch
(touch debounce = 1)
(release debounce = 0)
Figure 51 Touch and Release Example
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As soon as the ticks become larger than the CAP thresholds (see registers of the previous section) plus the
hysteresis (defined in register WhlHysteresis) the debounce counter starts.
In the example of Figure 51 the touch is validated after 2 samples (WhlCfg [1:0] = 01).
The release is detected immediately (WhlCfg [3:2] = 00) at the first sample with a pressure equal to zero.
The position of a finger on a wheel is calculated by the centre of gravity algorithm.
=
=
= 1
0
1
0
))()(_(
))()(_(*
32 N
i
N
i
iCapThreshidiffticks
iCapThreshidiffticksi
WhlNorm
WhlPos
- N is the number of sensors,
- A sensor with ticks smaller than the CapThreshold is not taken into account for calculating the position,
- WhlNorm[15:0] is a 16 bit number determined by WhlNormMsb[15:8] and WhlNormLsb[7:0].
- WhlPos is the wheel position (16 bits) which can be read by the host over the I2C registers WhlPosMsb and
WhlPosLsb
Figure 52 W heel Posit ion
Figure 52 shows an example of a wheel composed of 4 sensors (CAP0, CAP1… CAP3).
The default wheel norm value 512 (WhlNormMsb = 0x02, WhlNormLsb = 0x00), is taken for the example.
A touch on CAP0 gives the wheel position: 0.
A touch on CAP1 gives the wheel position: 16.
A touch on CAP3 gives the wheel position: 32.
If a touch occurs on CAP0 and CAP1 the centre of gravity algorithm will interpolate.
Assuming the touch is identically distributed on CAP0 and CAP1 then the position will be: 8
Assuming the touch is identically distributed on CAP1 and CAP2 then the position will be: 24
Assuming the touch is identically distributed on CAP2 and CAP3 then the position will be: 40
The minimum position of a wheel equals 0.
The maximum position is obtained if the finger is very slightly on CAP3 and heavily on CAP0.
The maximum position (WhlPosMax) is defined by:
N
WhlNorm
WhlPosMax ×= 32
with:
N is the number of sensors in the wheel
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WhlOffset
The wheel offset adds an offset to the wheel position.
Therefore the wheel is divided in 256 segments. Examples are shown in Figure 53.
If the offset equals zero then the calculated position remains unchanged.
If the offset is set to 64, that means an angle offset of 64/256 * 360 degree, the position zero will be shifted
90°.
If the off set is set to 128, that means an angle of fset of 128/256 * 3 60 degree, the posit ion zero will b e shifted
180°.
If the off set is set to 192, that means an angle of fset of 192/256 * 3 60 degree, the posit ion zero will b e shifted
270°.
Figure 53 W heel Posit ion zero with different off sets
Slow varying wheel ticks due to environmental changes are handled as buttons in the previous section.
If the ticks pass below the wheel negative threshold for more than the compensation negative max counter then
an offset compensation phase will be triggered.
If the ticks pass above the wheel average positive threshold then the averaging filters will be held.
A finger that moves very slowly over the wheel is not considered as a rotation. The status rotate clockwise and
rotate counter clockwise will not be set.
A finger that moves faster on the wheel will change the rotation status.
A rotation is detected if the difference of the position for two succeeding samples at the scanning rate goes
beyond the rotation threshold (WhlRotateThresh). A large rotation threshold requires very rapid finger rotations,
while a small rotation threshold detects more easily rotations but gets sensitive to noise variations as well.
WhlCfg
In noisy environments it may be required to debounce the touch and release detection decision.
In case the debounce is enabled th e SX8647 will count up to the num ber of debounce sam ples W hlCfg [1:0],
WhlCfg [3:2] before taking a touch or release decision. The sample period is identical to the scan period.
WhlAvgThresh
Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value.
In case the ticks get slightly positive this is considered as normal operation. Very large positive tick values
indicate a valid touch. The averaging filter is disabled as soon as the average reaches the value defined by
WhlAvgThresh. This mechanism avoids that a valid touch will be averaged and finally the tick difference
becomes zero.
In case three or more sensors reach the WhlAvgThresh value simultaneously then the SX8647 will start an
offset compensation procedure.
Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value.
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In case the ticks get slightly negative this is considered as normal operation. However large negative values will
trigger an offset compensation phase and a new set of DCVs will be obtained.
The decision to trigger a compensation phase based on negative ticks is determined by the value in the register
WhlCompNegThresh and by the number of ticks below the negative thresholds defined in register
WhlCompNegCntMax. An example is shown in Figure 50.
ticks_diff
Figure 54 Negative Ticks Offset Compensation Trigger
WhlCompNegThresh
Small negative ticks are considered as normal operation and will occur very often.
Larger negative ticks however need to be avoided and a convenient method is to trigger an offset
compensation phase. The new set of DCV will assure the idle ticks will be close to zero again.
A trade-off has to be found for the value of this register. A negative threshold too close to zero will trigger a
compensation phase very often. A very negative threshold will never trigger.
WhlCompNegCntMax
As soon as the ticks get smaller than the Negative Threshold the Negative Counter starts to count.
If the counter goes beyond the Negative Counter Max then the offset compensation phase is triggered.
The re comm ended va lue f or this r egister is ‘1 ’ which m eans that th e off set c ompens ation s tarts on the fir st tick
below the negative threshold.
W hlHysteresis
In case the pressure is larger as the wheel hysteresis the wheel status is touched.
WhlStuckAtTimeout
The stuckat timer can avoid sticky sensors.
If the stuc kat timer is set to one sec ond then th e touch of a f inger will las t only for one second an d consid ered
released, even if the finger remains on the wheel for a longer time. After the actual finger release the wheel
can be touched again and will be reported as usual.
In case the stuckat timer is not required it can be set to zero.
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5.6 Mapping Parameters
Mapping Parameters
Address Name Bits Description
7:3 Reserved 0x33 MapWakeupSize
2:0 Doze -> Active wake up sequence size.
0: Any sensor event (default)
1: key0
2: key0, key1
6: key0, key1,…key5
7: No sensor event, only GPI or I2C cmd can exit Doze mode
Each key must be followed by a release to be validated.
Any other sensor event before the release is ignored.
Any wrong key implies the whole sequence to be entered again.
7:4 key5 0x34 MapWakeupValue0
3:0 key4
7:4 key3 0x35 MapWakeupValue1
3:0 key2
7:4 key1 0x36 MapWakeupValue2
3:0 key0
Defines the sensor event associated to each key.
0x00: Btn0 (default)
0x01: Btn1
0x07: Btn7
0x08…0x0B: Reserved
0x0C : Wheel Touch
0x0D: Rotate Counter Clockwise
0x0E: Rotate Clockwise
0x0F: Reserved
7:4 GPIO[7] 0xC 0x37 MapAutoLight0
3:0 GPIO[6] 0xC
7:4 GPIO[5] 0xC 0x38 MapAutoLight1
3:0 GPIO[4] 0xC
7:4 GPIO[3] 0x3 0x39 MapAutoLight2
3:0 GPIO[2] 0x2
7:4 GPIO[1] 0x1 0x3A MapAutoLight3
3:0 GPIO[0]
Defines the mapping between GPOs
(with Autolight ON) and sensor events.
0x00: Btn0 (default)
0x01: Btn1
0x07: Btn7
0x08…0x0B: Reserved
0x0C: Group0 as defined by MapAutoLightGrp0
0x0D: Group1 as defined by MapAutoLightGrp1
0x0E: Rotate Counter Clockwise
0x0F: Rotate Clockwise
Several GPOs can be mapped to the same sensor
event and will be controlled simultaneously.
default
0x0
7 Reserved
6 Segment
5 Rotate Clockwise
4 Rotate Counter Clockwise
0x3B MapAutoLightGrp0Msb
3:0 Reserved
7 Btn7
6 Btn6
5 Btn5
4 Btn4
3 Btn3
2 Btn2
0x3C MapAutoLightGrp0Lsb
1 Btn1
Defines Group0 sensor events:
0: OFF
1: ON
default 0x4000
If any of the enabled sensor events occurs the
Group0 event will occur as well.
All sensors events within the group can be
independently set except wheel event Segment
which is exclusive (ie must be the only one
enabled to be used)
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Mapping Parameters
Address Name Bits Description
0 Btn0
7 Reserved
6 Wheel Touch
5 Rotate Clockwise
4 Rotate Counter Clockwise
0x3D MapAutoLightGrp1Msb
3:0 Reserved
7 Btn7
6 Btn6
5 Btn5
4 Btn4
3 Btn3
2 Btn2
1 Btn1
0x3E MapAutoLightGrp1Lsb
0 Btn0
Defines Group1 sensor events:
0: OFF (default)
1: ON
If any of the enabled sensor events occurs the
Group0 event will occur as well.
All sensors events within the group can be
independently set.
0x3F MapSegmentHysteresis 7:0 Defines the position hysteresis for detecting a segment change.
The hysteresis is def ined as a percentage of the maximum wheel pos iti on.
0x00: 0%
0x02: 2% (default)
0x64: 100%
This hysteresis applies to all segments of the wheel.
Table 20 Mapping Parameters
MapWakeupSize
The number of keys defining the wakeup sequence can be set from 1 to 6.
If the size is set to 0 then wakeup is done on any sensor event.
if the size is set to 6 then wakeup is done only by GPI or an I2C command.
MapWakeupValue0, MapWakeupValue1, MapWakeupValue2
For the wakeup sequence Btn2 -> Btn5 -> Btn6 ->Btn0 the required register settings are:
- MapWakeupSize set to 0x04,
- key0 = 0x2
- key1 = 0x5
=> MapWakeupValue2 set to 0x52
- key2 = 0x6
- key3 = 0x0
=> MapWakeupValue2 set to 0x06
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MapAutoLight0, MapAutoLight1, MapAutoLight2, MapAutoLight3
MapAutoLi ghtG rp0 Ms b, Ma pAut oL ightG r p 0Lsb, Map A utoL igh t Gr p1Msb, MapAuto Lig htG r p1Lsb
Thes e regis ter s d efine the mapping b et ween the G PO pi ns ( with Autolight ON) and the s e ns or inform ation wh ich
will control its ON/OFF state.
The mapping can be done to a specific sensor event but also on groups (in this case an y sensor event in the
group will contr ol the GPO ).
Table 21 defines for each selectable sensor event, which action will trigger corresponding GPO to switch ON
or OFF.
MapAutoLight GPO ON GPO OFF
BtnX Touch Release
Wheel Touch Touch Release
Wheel Rotation Clock Wise Rotation Clock Wise Rotation Clock Counter Wise or Release
Wheel Rotation Counter Clock Wise Rotation Counter Clock Wise Rotation Clock Wise or Release
Wheel Segment Segment Touched Segment Released
Table 21 Autolight Mapping, Sensor Inform ation
Examples:
- If GPO[0] should change state accordingly to Btn4 then MapAutoLight3[3:0] should be set to 0x04.
- If GPO[0] should change state accordingly to Btn0 or Btn1 then Group0 can be used as following:
- MapAutoLight3[3:0] should be set to 0x0C (ie Group0).
- MapAutoLightGrp0 should be set to 0x0003 (ie Btn0 or Btn1)
When the Wheel Segment event is mapped, the number of GPOs mapped to it determines the number of
wheel segments. The GPO with the lowest pin index is mapped on the segment with the smallest positions.
E.g. if two GPOs (e.g.GPO [0] and GPO[1]) ar e m apped to the W heel S egment e vent then the whee l is spl it in
two segments. GPO[0] will turn ON for a touch on the wheel segment [0, WhlPosMax/2] and GPO[1] for a
touch on the wheel segment [WhlPosMax/2, WhlPosMax].
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5.7 GPIO Parameters
GPIO Parameters
Address Name Bits Description
7:6 GPIO[7] Mode
5:4 GPIO[6] Mode
3:2 GPIO[5] Mode
0x40 GpioMode7_4
1:0 GPIO[4] Mode
7:6 GPIO[3] Mode
5:4 GPIO[2] Mode
3:2 GPIO[1] Mode
0x41 GpioMode3_0
1:0 GPIO[0] Mode
Defines the GPIO mode.
00: GPO (default)
01: GPP
10: GPI
11: Reserved
GPIO[7] Output Value at Power Up
GPIO[6] Output Value at Power Up
GPIO[5] Output Value at Power Up
GPIO[4] Output Value at Power Up
GPIO[3] Output Value at Power Up
GPIO[2] Output Value at Power Up
GPIO[1] Output Value at Power Up
0x42 GpioOutPwrUp 7:0
GPIO[0] Output Value at Power Up
Defines the values of GPO and GPP pins
after power up ie default values of I2C
parameters GpoCtrl and GppIntensity
respectively.
0: OFF(GPO) / IntensityOff (GPP) (default)
1: ON (GPO) / IntensityOn (GPP)
Bits corresponding to GPO pins with
Autolight ON should be left to 0.
Before being actually initialized GPIOs are
set as inputs with pull up.
GPIO[7] AutoLight
GPIO[6] AutoLight
GPIO[5] AutoLight
GPIO[4] AutoLight
GPIO[3] AutoLight
GPIO[2] AutoLight
GPIO[1] AutoLight
0x43 GpioAutoLight 7:0
GPIO[0] AutoLight
Enables Autolight in GPO mode
0 : OFF
1 : ON (default)
GPIO[7] Output Polarity
GPIO[6] Output Polarity
GPIO[5] Output Polarity
GPIO[4] Output Polarity
GPIO[3] Output Polarity
GPIO[2] Output Polarity
GPIO[1] Output Polarity
0x44 GpioPolarity 7:0
GPIO[0] Output Polarity
Defines the polarity of the GPO and GPP
pins.
0: Inverted (default)
1: Normal
0x45 GpioIntensityOn0
0x46 GpioIntensityOn1
0x47 GpioIntensityOn2
7:0 ON Intensity Index
Defines the ON intensity index
0x00: 0
0x01: 1
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GPIO Parameters
Address Name Bits Description
0x48 GpioIntensityOn3
0x49 GpioIntensityOn4
0x4A GpioIntensityOn5
0x4B GpioIntensityOn6
0x4C GpioIntensityOn7
0xFF: 255 (default)
0x4D GpioIntensityOff0
0x4E GpioIntensityOff1
0x4F GpioIntensityOff2
0x50 GpioIntensityOff3
0x51 GpioIntensityOff4
0x52 GpioIntensityOff5
0x53 GpioIntensityOff6
0x54 GpioIntensityOff7
7:0 OFF Intensity Index
Defines the OFF intensity index
0x00: 0 (default)
0x01: 1
0xFF: 255
GPIO[7] Function
GPIO[6] Function
GPIO[5] Function
GPIO[4] Function
GPIO[3] Function
GPIO[2] Function
GPIO[1] Function
0x56 GpioFunction 7:0
GPIO[0] Function
Defines the intensity index vs PWM pulse
width function.
0: Logarithmic (default)
1: Linear
GPIO[7] Fading Increment Factor
GPIO[6] Fading Increment Factor
GPIO[5] Fading Increment Factor
GPIO[4] Fading Increment Factor
GPIO[3] Fading Increment Factor
GPIO[2] Fading Increment Factor
GPIO[1] Fading Increment Factor
0x57 GpioIncFactor 7:0
GPIO[0] Fading Increment Factor
Defines the fading increment factor.
0: 1, intensity index incremented every
increment time (default)
1: 16, intensity index incremented every 16
increment times
GPIO[7] Fading Decrement Factor
GPIO[6] Fading Decrement Factor
GPIO[5] Fading Decrement Factor
GPIO[4] Fading Decrement Factor
GPIO[3] Fading Decrement Factor
GPIO[2] Fading Decrement Factor
GPIO[1] Fading Decrement Factor
0x58 GpioDecFactor 7:0
GPIO[0] Fading Decrement Factor
Defines the fading decrement factor.
0: 1, intensity index decremented every
decrement time (default)
1: 16, intensity index decremented every 16
decrement times
0x59 GpioIncTime7_6 7:4 GPIO[7] Fading Increment Time Defines the fading increment time.
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Touch Controller (8 sensors) with Enhanced LED Drivers
GPIO Parameters
Address Name Bits Description
3:0 GPIO[6] Fading Increment Time
7:4 GPIO[5] Fading Increment Time 0x5A GpioIncTime5_4
3:0 GPIO[4] Fading Increment Time
7:4 GPIO[3] Fading Increment Time 0x5B GpioIncTime3_2
3:0 GPIO[2] Fading Increment Time
7:4 GPIO[1] Fading Increment Time 0x5C GpioIncTime1_0
3:0 GPIO[0] Fading Increment Time
0x0: OFF (default)
0x1: 0.5ms
0x2: 1ms
0xF: 7.5ms
The total fading in time will be:
GpioIncTime*GpioIncFactor*
(GpioIntensityOn – GpioIntensityOff)
7:4 GPIO[7] Fading Decrement Time 0x5D GpioDecTime7_6
3:0 GPIO[6] Fading Decrement Time
7:4 GPIO[5] Fading Decrement Time 0x5E GpioDecTime5_4
3:0 GPIO[4] Fading Decrement Time
7:4 GPIO[3] Fading Decrement Time 0x5F GpioDecTime3_2
3:0 GPIO[2] Fading Decrement Time
7:4 GPIO[1] Fading Decrement Time 0x60
GpioDecTime1_0
3:0 GPIO[0] Fading Decrement Time
Defines the fading decrement time.
0x0: OFF
0x1: 0.5ms
0x2: 1ms
0x4: 2.0ms (default)
0xF: 7.5ms
The total fading out time will be:
GpioDecTime*GpioDecFactor*
(GpioIntensityOn – GpioIntensityOff)
7:4 GPIO[7] OFF Delay 0x61 GpioOffDelay7_6
3:0 GPIO[6] OFF Delay
7:4 GPIO[5] OFF Delay 0x62 GpioOffDelay5_4
3:0 GPIO[4] OFF Delay
7:4 GPIO[3] OFF Delay 0x63 GpioOffDelay3_2
3:0 GPIO[2] OFF Delay
7:4 GPIO[1] OFF Delay 0x64 GpioOffDelay1_0
3:0 GPIO[0] OFF Delay
Defines the delay after GPO OFF trigger
before fading out starts.
0x0: OFF (default)
0x1: 200ms
0x2: 400ms
0xF: 3000ms
7:6 GPIO[7] Pullup/down
5:4 GPIO[6] Pullup/down
3:2 GPIO[5] Pullup/down
0x65 GpioPullUpDown7_4
1:0 GPIO[4] Pullup/down
7:6 GPIO[3] Pullup/down
5:4 GPIO[2] Pullup/down
3:2 GPIO[1] Pullup/down
0x66 GpioPullUpDown3_0
1:0 GPIO[0] Pullup/down
Enables pullup/down resistors for GPI pins.
00 : None (default)
01 : Pullup
10 : Pulldown
11 : Reserved
7:6 GPI[7] Interrupt
5:4 GPI[6] Interrupt
3:2 GPI[5] Interrupt
0x67 GpioInterrupt7_4
1:0 GPI[4] Interrupt
7:6 GPI[3] Interrupt
5:4 GPI[2] Interrupt
0x68 GpioInterrupt3_0
3:2 GPI[1] Interrupt
Defines the GPI edge which will trigger INTB
falling edge and exit Sleep/Doze modes if
relevant.
00 : None (default)
01 : Rising
10 : Falling
11 : Both
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GPIO Parameters
Address Name Bits Description
1:0 GPI[0] Interrupt
GPI[7] Debounce
GPI[6] Debounce
GPI[5] Debounce
GPI[4] Debounce
GPI[3] Debounce
GPI[2] Debounce
GPI[1] Debounce
0x69 GpioDebounce 7:0
GPI[0] Debounce
Enables the GPI debounce (done on 10
consecutive samples at 1ms).
0 : OFF (default)
1 : ON
Table 22 GPIO Parameters
Table 23 resumes the applicable SPM and I2C parameters for each GPIO mode.
GPI GPP GPO
GpioMode X X X
GpioOutPwrUp X
1 X2
GpioAutoligth X
GpioPolarity X X
GpioIntensityOn X
1 X
GpioIntensityOff X
1 X
GpioFunction X X
GpioIncFactor X
GpioDecFactor X
GpioIncTime X
GpioDecTime X
GpioOffDelay X
GpioPullUpDown X
GpioInterrupt X
SPM
GpioDebounce X
IrqSrc[4] X
GpiStat X
GpoCtrl X
3
GppPinId X
I2C
GppIntensity X
1
1 At power up, GppIntensit y of each GPP pin is initialized with GpioIntens ityOn or Gpi oInt ensityOff depending on GpioOutPwrUp
corresponding bits val ue.
2 Only if Autolight is OFF, else must be left to 0 (default value)
3 Only if Autolight is OFF, else ignored
Table 23 Appl icable SPM/ I2C Parameters vs. GPIO Mode
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6 I2C INTERFACE
The I2C implemented on the SX8649 is compliant with:
- standard (100kb/s), fast mode (400kb/s)
- slave mode
- 7 bit address (default 0x2B). The default address can be changed in the NVM at address 0x04.
The host can use the I2C to read and write data at any time. The effective changes will be applied at the next
process ing phase (s ect ion 3.3).
Three types of registers are considered:
- status ( read). T hese r egisters give infor m ation about the status of the cap acit ive buttons , wheel, G PIs, oper atio n
modes etc…
- control (read/write). These registers control the soft reset, operating modes, GPIOs and offset compensation.
- SPM gateway (read/write). These registers are used for the communication between host and the SPM. The
SPM gateway communication is done typically at power up and is not supposed to be changed when the
application is running. The SPM needs to be re-stored each time the SX8649 is powered down.
The SPM c an be stored pe rmanentl y in the NVM m emory of the SX8649. T he SPM gate way comm unication over
the I2C at power up is then not required.
The I2C will be able to rea d and write from a start address and then perform read or writes sequentiall y, and the
address increments automatically.
The supported I2C access formats are described in the next sections.
6.1 I2C Write
The format of the I2C write is given in Figure 55.
After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The
SX8649 the n Acknowled ges [A] that it is bei ng addressed, and t he Master s ends an 8 bit Data Byte cons isting of
the SX864 9 Re gis ter Ad dr e ss ( RA) . T he Sla ve Ac k nowled ges [ A] a nd the m as ter s ends th e a ppr opriat e 8 bit Data
Byte (W D0). Again the Sla ve Acknowledg es [A]. In case the m aster needs to wr ite mor e data, a succeeding 8 bit
Data Byte will follow (WD1), acknowledged by the slave [A]. This sequence will be repeated until the master
terminates the transfer with the Stop condition [P].
Figure 55 I2C write
The regis ter addres s is inc rem ented autom atically whe n succ essive regis ter data (W D1...WD n) is supplied b y the
master.
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6.2 I2C read
The format of the I2C read is given in Figure 56.
After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The
SX8649 t hen Ack nowledge s [A] that it is being a ddress ed, and the Master responds with an 8 bit Da ta consis ting
of the Register Address (RA). The Slave Acknowledges [A] and the master sends the Repeated Start Condition
[Sr]. Once again, the slave address (SA) is sent, followed by an eighth bit (‘1’) indicating a Read.
The SX 8649 responds with an Ackno wle dge [A] and t he read Data b yte (RD 0). If the m aster needs to re ad more
data it will acknowledge [A] and the SX8649 will send the next read b yte (RD1). T his sequence can be repeated
until the master terminates with a NACK [N] followed by a stop [P].
Figure 56 I2C read
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6.3 I2C Registers Overview
Address Name R/W Description
0x00 IrqSrc read Interrupt Source
0x01 CapStatMsb read Wheel/Button Status MSB
0x02 CapStatLsb read Button Status LSB
0x03 WhlPosMsb read Wheel Position MSB
0x04 WhlPosLsb read Wheel Position LSB
0x05 Reserved
0x06 Reserved
0x07 GpiStat read GPI Status
0x08 SpmStat read SPM Status
0x09 CompOpMode read/write
Compensation and
Operating Mode
0x0A GpoCtrl read/write GPO Control
0x0B GppId read/write GPP Pin Selection
0x0C GppIntensity read/write GPP Intensity
0x0D SpmCfg read/write SPM Configuration
0x0E SpmBaseAddr read/write SPM Base Address
0x0F Reserved
0xAC SpmKeyMsb read/write SPM Key MSB
0xAD SpmkeyLsb read/write SPM Key LSB
0xB1 SoftReset read/write Software Reset
Table 24 I 2C Regist ers Overview
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6.4 Status Registers
Address Name Bits Description
7 Reserved
6 NVM burn interrupt flag
5 SPM write interrupt flag
4 GPI interrupt flag
3 Wheel interrupt flag
2 Buttons interrupt flag
1 Compensation interrupt flag
0x00 IrqSrc
0 Operating Mode interrupt flag
Interrupt source flags
0: Inactive (default)
1: Active
INTB goes low if any of
these bits is set.
More than one bit can be
set.
Reading IrqSrc clears it
together with INTB.
Table 25 I nt errupt Source
The delay between the actual event and the flags indicating the interrupt source may be one scan period.
IrqSrc[6] is set once NVM burn procedure is completed.
IrqSrc[5] is set once SPM write is effective.
IrqSrc[4] is set if a GPI edge as programmed in GpioInterrupt occurred. GpiStat shows the detailed status of the
GPI pins.
IrqSrc[3] is s et if a Wheel e vent oc c ur red ( touc h , rel ea s e, r otati on cl oc kwise, rot at ion c o unter c l oc k wise or p o s itio n
change) . CapStatMsb, WhlPosMsb and WhlPosLsb show the detailed status of the Wheel.
IrqSrc[2] is set if a Button event occurred (touch or release if enabled). CapStatMsb and CapStatLsb show the
detailed status of the Buttons.
IrqSrc[1] is set once compensation procedure is completed either through automatic trigger or via host request.
IrqSrc[0] is set when actual ly entering Activ e or Doze mode either through autom atic wakeup or vi a host request.
CompOpmode shows the current operation mode.
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Address Name Bits Description
7 Reserved
6 Wheel Rotation
Clockwise
5 Wheel Rotation
Counter Clockwise
Wheel Rotation status
0: No rotation (default)
1: Rotation
The status remains high as long as the wheel is
touched and no opposite rotation has occurred.
4 Wheel Touched Wheel Touch status
0: Released (default)
1: Touched
0x01 CapStatMsb
3:0 Reserved
7 Button 7 Touched
6 Button 6 Touched
5 Button 5 Touched
4 Button 4 Touched
3 Button 3 Touched
2 Button 2 Touched
1 Button 1 Touched
0x02 CapStatLsb
0 Button 0 Touched
Button Touch status
0: Released (default)
1: Touched
Table 26 Wheel, Button status MSB/LSB
Address Name Bits Description
0x03 WhlPosMsb 7:0 Wheel Position[15:8]
0x04 WhlPosLsb 7:0 Wheel Position[7:0]
Shows the current (touched) or last (released)
wheel position[15:0] unsigned (default 0x00)
Table 27 Wheel position MSB/LSB
Address Name Bits Description
0x07 GpiStat 7:0 GPI[7:0]
Status
Status of each individual GPI pin
0: Low
1: High
Bits of non-GPI pins are set to 0.
Table 28 I2C GPI status
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Address Name Bits Description
7:4 reserved
3 NvmValid
Indicates if the current NVM is valid.
0: No – QSM is used
1: Yes – NVM is used
0x08 SpmStat
2:0 NvmCount
Indicates the number of times NVM has been burned:
0: None – QSM is used (default)
1: Once – NVM is used if NvmValid = 1, else QSM.
2: Twice – NVM is used if NvmValid = 1, else QSM.
3: Three times – NVM is used if NvmValid = 1, else QSM.
4: More than three times – QSM is used
Table 29 I 2C SPM status
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6.5 Control Registers
Address Name Bits Description
7:3 Reserved*, write only ‘00000’
2 Compensation
Indicates/triggers compensation procedure
0: Compensation completed (default)
1: read -> compensation running ; write -> trigger
compensation
0x09 CompOpMode
1:0 Operating Mode
Indicates/programs** operating mode
00: Active mode (default)
01: Doze mode
10: Sleep mode
11: Reserved
Table 30 I 2C com pensat ion, operation modes
* The reading of these reserved bits will return varying values.
** After the operating mode change (Active/Doze) the host should wait for INTB or 300ms before
performing any I2C read access.
Address Name Bits Description
0x0A GpoCtrl 7:0 GpoCtrl[7:0]
Triggers ON/OFF state of GPOs when Autolight is
OFF
0: OFF (ie go to IntensityOff)
1: ON (ie go to IntensityOn)
Default is set by SPM parameter GpioOutPwrUp
Bits of non-GPO pins are ignored.
Table 31 I2C GPO Control
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Address Name Bits Description
7:3 Reserved, write only ‘00000’
0x0B GppPinId 2:0 GPP Pin Identifier
Defines the GPP pin to which the GppIntensity is
assigned for the following read/write operations
0x0 = GPP0 (default)
0x1 = GPP1
...
0x7 = GPP7
GPPx refers to pin GPIOx configured as GPP
Table 32 I2C GPP Pin Identifier
Address Name Bits Description
0x0C GppIntensity 7:0
Defines the intensity index of the GPP pin selected in GppPinId
0x00: 0
0x01: 1
0xFF: 255
Reading returns the intensity index of the GPP pin selected in GppPinId.
Default value is IntensityOn or IntensityOff depending on GpioOutPwrUp.
Table 33 I2C GPP Intensity
Address Name Bits Description
0xB1 SoftReset 7:0 Writing 0xDE followed by 0x00 will reset the chip.
Table 34 I2C Soft Reset
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6.6 SPM Gateway Registers
The SX8649 I2C interface offers two registers for exchanging the SPM data with the host.
SpmCfg
SpmBaseAddr
Address Name Bits Description
7:6 00: Reserved
5:4
Enables I2C SPM mode
00: OFF (default)
01: ON
10: Reserved
11: Reserved
3 Defines r/w direction of SPM
0: SPM write access (default)
1: SPM read access
0x0D SpmCfg
2:0 000: Reserved
Table 35 SPM access configuration
Address Name Bits Description
0x0E SpmBaseAddr 7:0 SPM Base Address (modulo 8).
The lowest address is 0x00 (default).
The highest address is 0x78.
Table 36 SP M Base Ad dress
The exchange of data, read and write, between the host and the SPM is always done in bursts of eight bytes.
The base address of each burst of eight bytes is a modulo 8 number, starting at 0x00 and ending at 0x78.
The registers SpmKeyMsb and SpmKeyLsb are required for NVM programming as described in section 6.7.
Address Name Bits Description
0xAC SpmKeyMsb 7:0 SPM to NVM burn Key MSB Unlock requires writing data: 0x62
Table 37 SPM Key MSB
Address Name Bits Description
0xAD SpmKeyLsb 7:0 SPM to NVM burn Key LSB Unlock requires writing data: 0x9D
Table 38 SPM Key LSB
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6.6.1 SPM Write Sequence
The SPM write can be done in any mode (Active, Doze, Sleep). Writing the SPM in Sleep is useful to avoid
potential transient behaviors.
The SPM must always be written in blocks of 8 bytes. The sequence is described below:
1. Set the I2C in SPM mode by writing “01” to SpmCfg[5:4] and SPM write access by writing ‘0’ to SpmCfg[3].
2. Write the SPM base address to SpmBaseAddr (The base address needs to be a value modulo 8).
3. Write the eight consecutive bytes to I2C address 0, 1, 2, …7
4. Terminate by writing “000” to SpmCfg[5:3].
Figure 57: SP M Write Sequ enc e
The complete SPM can be written by repeating 16 times the cycles shown in Figure 57 using base addresses
0x00, 0x08, 0x10, …, 0x70, 0x78. Between each sequence the host should wait for INTB (Active/Doze) or 30ms
in Sleep.
In Active or Doze mode, once the SPM write sequence is actually applied, the INTB pin will be asserted and
IrqSrc[5] set. In Sleep mode the SPM write can be actually applied with a delay of 30ms.
The host clears the interrupt and IrqSrc[5] by reading the IrqSrc register.
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6.6.2 SPM Read Sequence
The SPM read can be done in any mode (Active, Doze, Sleep).
The SPM must always be read in blocks of 8 bytes. The sequence is described below:
1. Set the I2C in SPM mode by writing “01” to SpmCfg[5:4] and SPM read access by writing ‘1’ to SpmCfg[3].
2. Write the SPM base address to SpmBaseAddr (The base address needs to be a value modulo 8).
3. Read the eight consecutive bytes from I2C address 0, 1, 2, …7
4. Terminate by writing “000” to SpmCfg[5:3].
Figure 58: SP M Read Sequ enc e
The c omplete SPM c an be read b y repeati ng 16 tim es the cycles s hown in Fig ure 58 using bas e addr esses 0x00,
0x08, 0x10, …, 0x70, 0x78.
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6.7 NVM burn
The content of the SPM can be copied permanently (burned) into the NVM to be used as the new default
parameters. The burning of the NVM can be done up to three times and must be done only when the SPM is
completely written with the desired data. The NVM burn must be done in Active or Doze mode.
Once the NVM burn process is terminated IrqSrc[6] will be set and INTB asserted.
After a reset the burned NVM parameters will be copied into the SPM.
The number of times the NVM has been burned can be monitored by reading NvmCount from the I2C register
SpmStat[2:0].
Figure 59 Simplified Diagram NvmCount
Figure 59 shows the simplified diagram of the NVM counter. The SX8649 is delivered with empty NVM and
NvmCount set to zero. The SPM points to the QSM.
Each NVM burn will increase the NvmCount. At the fourth NVM burn the SX8649 switches definitely to the QSM.
The burning of the SPM into the NVM is done by executing a special sequence of four I2C commands.
1. Write the data 0x62 to the I2C register I2CKeyMsb. Terminate the I2C write by a STOP.
2. Write the data 0x9D to the I2C register I2CKeyLsb. Terminate the I2C write by a STOP.
3. Write the data 0xA5 to the I2C register I2CSpmBaseAddr. Terminate the I2C write by a STOP.
4. Write the data 0x5A to the I2C register I2CSpmBaseAddr. Terminate the I2C write by a STOP.
This is illustrated in Figure 60.
SSA 00x0EA0xA5A PA
S : Star t c o nd ition
SA : Slave address
A : Slave acknowledge
P : Stop c onditi on
From master to slave
From slave to master
SSA 00x0EA0x5AA PA
3)
4)
SSA 00xAC
A0x62A PA
SSA 00xADA0x9DA PA
1)
2)
Figure 60: NVM burn proce dur e
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7 AP PLICATION INFORMATION
A typical application schematic is shown in Figure 61.
Figure 61 Typical Application
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8 PACKAGING INFORMATION
8.1 Package Outline Drawing
SX8649 is assembled in a MLPQ-UT28 package as shown in Figure 62.
INDICATOR
(LASER MARK)
PIN 1
DIMENSIONS
NOM
INCHES
N
bbb
aaa
A2
A1
E1
D1
DIM
L
e
E
D
A
b
MIN MAX
MILLIMETERS
MINMAX NOM
.154 .157 .161 3.90 4.00 4.10
.154 .157 .161 3.90 4.00 4.10
.003
.006
.100
28
.008
.104
.000
.020
(.006)
0.08
0.20
28
.010
.108
0.15
2.55
.024
.001 0.00
0.50
2.75
0.25
2.65
0.02
0.60
(0.152)
.004 0.10
2.55 2.65 2.75
0.40 BSC.016 BSC 0.30.012 .020.016 0.40 0.50
.108.104.100
2
1
SEATING
PLANE
N
CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).
COPLANARITY APPL IES TO TH E EXPOSED PAD AS WELL AS THE TERMINALS.
1.
2.
NOTES:
-
--
-
D
E
AB
A1
A
aaa C
A2
C
D1
E1
LxN
E/2
e
bbb CAB
D/2 bxN
Figure 62 Package Outline Drawing
8.2 Land Pattern
The land pattern of MLPQ-UT28 package, 4 mm x 4 mm is shown in Figure 63.
Figure 63 Land Pattern
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Contact Infor mation
© Semtech 2010
A
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copyright o wner. The i nform ation presente d in this do cument does not form part of an y quotation or contract , is
believed to be accurate and reliable and may be changed without notice. No liability will be accepted by the
publisher for any consequence of its use. Publication thereof does not convey nor imply any license under
patent or other industrial or intellectual property rights. Semtech assumes no responsibility or liability
whatsoever for any failure or unexpected operation resulting from misuse, neglect improper installation, repair
or improper handling or unusual physical or electrical stress including, but not limited to, exposure to
parameters beyond the specified maximum ratings or operation outside the specified range.
SEMTECH PRODUCTS ARE NOT DESIGNED, INTENDED, AUTHORIZED OR WARRANTED TO BE
SUITABLE FOR USE IN LIFE-SUPPORT APPLICATIONS, DEVICES OR SYSTEMS OR OTHER CRITICAL
APPLICATIONS. INCLUSION OF SEMTECH PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO
BE UND ERT AKE N SO LE L Y AT THE CU STOMER’ S OWN RISK. Sho uld a c us t omer pur c hase or us e Semtech
products f or an y such unaut horized a pplicat ion, the c ustom er shall ind em nif y and hold Sem tech and its officer s,
employees, subsidiaries, affiliates, and distributors harmless against all claims, costs damages and attorney
fees which could arise.
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Phone: (805) 498-2111 Fax: (805) 498-3804
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