WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
1
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
GENERAL DESCRIPTION
The SX8636 is an ultr a low power, full y integrated 8-
channel solution for capacitive touch-buttons and
proximity detection applications. Unlike many
capacitive touch solutions, the SX8636 features
dedicated capacitive sense inputs (that requires no
external components) in addition to 8 general
purpose I/O ports (GPIO). Each GPIO is typically
configured as LED driver with independent PWM
source f or enhanc ed lighti n g c ontr ol suc h as intensit y
and fading.
The SX8636 i nclu des a c a pac itiv e 10 bit ADC analog
interface with automatic compensation up to 100pF.
The high resolution capacitive sensing supports a
wide variety of touch pad sizes and shapes and
allows capacitive buttons to be created using thick
overlay materials (up to 5mm) for an extremely
robust and ESD immune system design.
The SX8636 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 SX8636 supports the 400 kHz I²C serial bus
data protocol and includes a field programmable
slave addr ess. The tin y 4m m x 4mm f ootprint mak es
it an ideal solution for portable, battery powered
applications where power and density are at a
premium.
TYPICAL APPLICAT ION CIRCUIT
proximity
SX8636
cap2
cap3
cap4
cap5
cap6
cap7
gnd
gpo5
gpo4
gpo3
gpo2
gpo1
gnd
gpo0
vana
resetb
gnd
gpo7
vdig
gpo6
cn
cp
vdd
scl
intb
sda
analog
sensor
interface
micro
processor
RAM
ROM
NVM
I2C
GPIO
controller
power management
clock
generation
RC
PWM
LED
controller
bottom plate
HOST
cap0
cap1
d1
d0
d2
d3
d4
d5
d6
d7
d0
d1
d2
d3
d4
d5
d6
d7
KEY PRODUCT FEATURES
Complete eight Sensors Capacitive Touch Controller for
Buttons
Pre-configured for eight Buttons
Eight LED Drivers with Individual Intensity, Fading
Control and Autolight Mode
256 steps PWM Linear and Logar it hm ic contr ol
Proximity Sensing up to several centimetres
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 Pow er-up and Configurable Intervals
Multi-Time In-Field Programmable Firmware Parameters
for Ultimate Flexibility
On-chip user programmab le mem ory for fast, sel f
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/Por t abl e/H andhe ld co mput er s
Cell phones, PDAs
Consumer Products, Instrumentation, Automotive
Mechanical Button Replacement
ORDERING INFORMATION
Part Number
Temperature
Range
Package
SX8636I05AULTRT
1
-40°C to +85°C
Lead Free MLPQ-UT28
1 3000 Units/reel
* This device is RoHS/WEEE compliant and Halogen Free
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
2
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
Table of Contents
GENERAL DESCRIPTION ........................................................................................................................ 1
TYPICAL APPLICAT ION 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 Diagram 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 Qu ickstart Applicatio n 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 Period 12
3.4 Operation modes 12
3.5 Sensors on the PCB 14
3.6 Button Information 14
3.6.1 Button Information 14
3.7 Analog Sensing In terface 15
3.8 Offset Compensation 16
3.9 Processing 17
3.10 Configuration 17
3.11 Power Management 19
3.12 Clock Circuitry 19
3.13 I2C interface 19
3.14 Reset 20
3.14.1 Power up 20
3.14.2 RESETB 20
3.14.3 Software Reset 21
3.15 Interrupt 22
3.15.1 Power up 22
3.15.2 Assertion 22
3.15.3 Clearing 22
3.15.4 Example 23
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
3
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
3.16 General Purpose Input and Outputs 23
3.16.1 Introduction and Definitions 23
3.16.2 GPI 24
3.16.3 GPP 24
3.16.4 GPO 25
3.16.5 Intensity index vs PWM pulse width 28
3.17 Smart Wake Up 29
4 PIN DESCRIPTIONS ..................................................................................................................... 30
4.1 Introduction 30
4.2 ASI pins 30
4.3 Host interface pins 31
4.4 Power management pins 34
4.5 General purpose IO pins 35
5 DETAILED CONFIGURATION DESCRIPTIONS .............................................................................. 36
5.1 Introduction 36
5.2 General Parameters 39
5.3 Capacit iv e Sensors Para met ers 40
5.4 Button Parameters 44
5.5 Mapping Parameters 48
5.6 GPIO Parameters 50
6 I2C INTERFACE ........................................................................................................................... 54
6.1 I2C Write 54
6.2 I2C read 55
6.3 I2C Registers Overview 56
6.4 Status Registers 57
6.5 Control Registers 59
6.6 SPM Gateway Registers 61
6.6.1 SPM Write Sequence 62
6.6.2 SPM Read Sequence 63
6.7 NVM burn 64
6.8 Monitor Mode 65
7 APPLICATION INFORMATION ...................................................................................................... 66
7.1 Typical Application Schematic 66
7.2 Example of Touch+Proximity Module 67
7.2.1 Overview 67
7.2.2 Operation 67
7.2.3 Performance 67
7.2.4 Schematics 68
7.2.5 Layout 69
8 REFERENCES ............................................................................................................................. 70
9 PACKAGING INFORMATION ........................................................................................................ 71
9.1 Package Outline Drawing 71
9.2 Land Pattern 71
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
4
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
1 GENERAL DESCRIPTION
1.1 Pin Diagram
SX8636
Top View
1
2
3
4
5
6
7
21
20
19
18
17
16
15
89 10 11 12 13 14
22
23
2425
2627
28
bottom ground pad
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
FM26
yyww
xxxxx
R05
yyww = Date Code
xxxxx = Semtech lot number
R05 = Semtech Code
Figure 2 Marking I nf ormation
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
5
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
1.3 Pin Description
Number Name Type Description
1
CAP1
Capacitive Sensor 1
2
CAP2
Capacitive Sensor 2
3
CAP3
Capacitive Sensor 3
4
CAP4
Capacitive Sensor 4
5
CAP5
Capacitive Sensor 5
6
CAP6
Capacitive Sensor 6
7
CAP7
Capacitive Sensor 7
8
CN
Integration Capacitor, negative terminal (1nF between CN and CP)
9
CP
Integration Capacitor, positive terminal (1nF between CN and CP)
10
VDD
Main input power supply
11
INTB
Interrupt, active LOW, requires pull up resistor (on host or external)
12
SCL
I2C Clock, requires pull up resistor (on host or external)
13
SDA
I2C Data, requires pull up resistor (on host or external)
14
GPIO0
General Purpose Input/Output 0
15
GPIO1
General Purpose Input/Output 1
16
GND
Ground
17
GPIO2
General Purpose Input/Output 2
18
GPIO3
General Purpose Input/Output 3
19
GPIO4
General Purpose Input/Output 4
20
GPIO5
General Purpose Input/Output 5
21
GND
Ground
22
GPIO6
General Purpose Input/Output 6
23
GPIO7
General Purpose Input/Output 7
24
VDIG
Digital Core Decoupling, connect to a 100nF decoupling capacitor
25
GND
Ground
26
RESETB
Active Low Reset. Connect to VDD if not used.
27
VANA
Analog Core Decoupling, connect to a 100nF decoupling capacitor
28
CAP0
Capacitive Sensor 0
bottom plate
GND
Exposed pad connec t to grou n d
Table 1 Pin descr ipt ion
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
6
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
1.4 Simplified Block Diagram
The simplified block diagram of the SX8636 is illustrated in Figure 3.
SX8636
cap2
cap3
cap4
cap5
cap6
cap7
gnd
gpo5
gpo4
gpo3
gpo2
gpo1
gnd
gpo0
vana
resetb
gnd
gpo7
vdig
gpo6
cn
cp
vdd
scl
intb
sda
analog
sensor
interface
micro
processor
RAM
ROM
NVM
I2C
GPIO
controller
power management
clock
generation
RC
PWM
LED
controller
bottom plate
cap0
cap1
Figure 3 Simplified block diagram of the SX8636
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 Memory
PWM Pulse Width Modulation
QSM Quick Start Memory
SPM Shadow Parameter Memory
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
7
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
2 ELECTRICAL CHARACTERISTICS
2.1 Absolute Ma ximum 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)
V
IN
-0.5
3.9
V
Input current (n on-supply pins)
I
IN
10
mA
Operating Junction Temperature
T
JCT
125
°C
Reflow temperature
T
RE
260
°C
Storage temperature
T
STOR
-50
150
°C
ESD HBM (Human Body model)(i)
ESD
HBM
3
kV
Latchup(ii)
I
LU
± 100
mA
Table 2 Absolute Maximum Ratings
(i) Tested to JEDEC standard JESD 22-A114
(ii) Tested to JEDEC standar d JES D78
2.2 Recommended Operating Conditions
Parameter Symbol Min. Max. Unit
Supply Voltage
VDD
2.7V
3.6
V
Supply Voltage Drop(iii, iv, v)
VDD
drop
100
mV
Supply Voltage for NVM programming
VDD
3.6
3.7
V
Ambient Temperature Range
T
A
-40
85
°C
Table 3 Recommended Oper at ing 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 SX8636 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 cyc le, it is recomm ended that the host also resets
the SX8636 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)
θ
JA
25
°C/W
Table 4 Thermal Charac terist ics
(vi) Static airflow
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
8
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
2.4 Electrical Spec if icat ions
All values are valid within the operating conditions unless otherwise specified.
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
Current consumption
Active mode, average
I
OP,active
30ms scan period,
8 sensors enabled,
minimum sensitivity
175
225
uA
Doze mode, average
I
OP,Doze
195ms scan period,
8 sensors enabled,
minimum sensitivity
80
110
uA
Sleep
I
OP,sleep
I2C and GPI listening,
sensors disabled
8
17
uA
GPIO, set as Input, RESETB, SCL, SDA
Input logic high
V
IH
0.7*VDD
VDD + 0.3V
V
Input logic low
V
IL
VSS applied to GND pins
VSS - 0.3V
0.8
V
Input leakage cur rent
L
I
CMOS input
±1
uA
Pull up resistor
R
PU
when enabled
660
kΩ
Pull down resistor
R
PD
when enabled
660
kΩ
GPIO set as Output, INTB, SDA
Output logic high
V
OH
I
OH
<4mA
VDD-0.4
V
Output logic low
V
OL
I
OL,GPIO
<12mA
IOL,SDA,INTB<4mA
0.4
V
Start-up
Power up time
t
por
time between risi ng edge
VDD and rising INTB
150
ms
RESETB
Pulse width
t
res
50
ns
Recommended External components
Capacitor between VDIG, GND
C
vdig
type 0402, tolerance +/-50%
100
nF
Capacitor between VANA, GND
C
vana
type 0402, tolerance +/-50%
100
nF
Capacitor between CP, CN
C
int
type 0402, COG, tolerance +/-5%
1
nF
Capacitor between VDD, GND
C
vdd
type 0402, tolerance +/-50%
270
nF
Table 5 Elect r ical Specifications
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
9
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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 cond itio n setup tim e
tSU;STO
0.6
us
Bus free time between stop and start
tBUF
500
us
Input glitch suppr e ssion
tSP
50
ns
Table 6 I2C Timing Specificat ion
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”
SDA
SCL
tSU;STA tHD;STA tSU;STO tBUF
70%
30%
70%
Figure 4 I2C St ar t and Stop timing
SDA
SCL
t
LOW
t
HIGH
t
HD;DAT
t
SU;DAT
t
SP
70%
30%
70%
30%
Figure 5 I 2C Data t iming
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
10
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
3 FUNCTIONAL DESCRIPTIO N
3.1 Quickstart Application
The SX8636 is preconfigured (Quickstart Application) for an application with eight buttons and eight LED drivers
using logarithmic PWM fading.
Implem enting a sc hem atic based on Figure 6 wil l be imm ediately operationa l after powerin g without pr ogr am ming
the SX8636 (even wit hout hos t).
HOST
SX8636
cap2
cap3
cap4
cap5
cap6
cap7
gnd
gpo5
gpo4
gpo3
gpo2
gpo1
gnd
gpo0
vana
resetb
gnd
gpo7
vdig
gpo6
cn
cp
vdd
scl
intb
sda
analog
sensor
interface
micro
processor
RAM
ROM
NVM
I2C
GPIO
controller
power management
clock
generation
RC
PWM
LED
controller
bottom plate
cap0
cap1
d1
d0
d2
d3
d4
d5
d6
d7
d0
d1
d2
d3
d4
d5
d6
d7
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.
All other sensors (CAP1 to CAP7) have their own LED associated on a GPIO pin showing a touch or a release.
The sensor detection and the LED fading described above are operational without any host interaction.
This is made possible using the SX8636 Autolight feature described in the following sections.
3.2 Introduction
3.2.1 General
The SX8636 is intended to be used in applications which require capacitive sensors covered by isolating overlay
material and which need to detect the proximity of a finger/hand though the air. A finger approaching the
capacitive sensor s will c hange the charge that ca n be lo aded on t he sensor s. The SX8636 m easures the ch ange
of char ge and conver ts th at into d igit al v alu es (tick s) . The larger the char ge on t he sens ors, the lar ger the n umber
of ticks will be. The charge to ticks conversion is done by the SX8636 Analog Sensor Interface (ASI).
The ticks are further processed by the SX8636 and converted in a high level, easy to use information for the
user’s host.
The information between SX8636 and the user’s host is passed through the I2C interface with an additional
interrupt signal indicating that the SX8636 has new information. For buttons t his information is simply touched or
released.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
11
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
3.2.2 GPIOs
A second path of feedback to the user is using General Purpose Input Output (GPIO) pins. The SX8636 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 SX8636 has eight individual PWM generators, one for each GPIO pin.
The LED fading can be initiated automatically by the SX8636 by setting the SX8636 Autolight feature. A simple
touch on a sensor and the c orr espondi ng LED will fad e-in with out any host interac tion over the I2C.
In case the Autolight featur e is disa bled t hen t he host w ill decid e to s tart a LED fadi ng-in per iod, sim pl y b y setting
the GP0 pin to ‘high’ using one I2C command. The SX8636 will then slowly fade-in the LED using the PWM
autonomously.
In case th e hos t needs t o h ave full c ontrol of the L ED i ntensi 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 SX8636 has many low level built-in, fixed algorithms and procedures. To allow a lot of freedom for the user
and adapt the SX8636 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, which GPIO is used for outputs or LEDs and which GPIO is mapped to which button.
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
SX8636 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 SX8636. The programming needs to be done once (over the I2C). The SX8636 will then
boot up from the NVM and additional parameters from the host are not required anymore.
In case the host desires to overwrite the boot-up NVM parameters (partly or even complete) this can be don e by
additional I2C communications.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
12
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
3.3 Scan Period
The basic operation Scan period of the SX8636 sensing interface can be split into three periods over time.
In the first period (Sensing) the SX8636 is sensing all enabled CAP inp ut s , from CAP0 towards CAP7.
In the sec o nd per iod (Processing) the SX8636 proc esses the sensor d ata, verifie s and updat es th e G PI O a n d I2C
status registers.
In the third period (Timer) the SX8636 is set in a low power mode and waits until a new cycle starts.
Figure 7 shows the different SX8636 periods over time.
CAP0
CAP1
CAP7
sensing
data
processing
processing timer
CAP0
CAP1
scan period
time
timer
Figure 7 Scan Period
The sc an period det erm ines the m inim um r eaction time of th e SX8636. T he scan peri od c an be co nfigur ed b y the
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 SX8636
generates the interrupt on the INTB pin. The shorter the scan period the faster the reaction time will be.
Very low power consum ption c an be obtained by setting v ery long s can p er io ds with th e expense of ha vi ng lo nger
reaction times.
Important: All external e ve nts like GPIO, I 2C a nd INTB are upd ate d i n th e pr ocessing period, so o nc e e very sc an
period. If e.g. a GPI would change sta te directl y after t he processin g period then t his will be r eported with a delay
of one scan period later in time.
3.4 Operation modes
The SX8636 has 3 op eratio n m odes. The main dif f er en ce is f ound in the re actio n tim 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 opera tin g c urr ent.
Sleep mode turns the SX8636 OFF, except for the I2C and GPI peripheral, minimizing operating current while
maintaining the pow er supp lies. In Sleep mode the SX8636 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 applications the re action t ime needs to be fas t when fing ers ar e present, but can be s lo w when no per son
uses the application. In case the SX8636 is not used for a specific time it can go from Active mode into Doze
mode and p ower wi ll be saved . Th is tim e-out is det ermined by the P assive T imer which ca n be config ured by the
user or turned OFF if not required.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
13
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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 SX8636 offers therefore a smart wake-up sequence feature in which the user needs to touch and release a
correct sequence of buttons bef ore Active m ode will be entered. This is explained in more detail in t he 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 SX8636.
The diagram in Figure 8 sh o ws the avai lab le op eration modes and the possible transitions.
ACTIVE mode
DOZE mode
SLEEP mode
wake-up
sequence
detected
OR
GPI interrupt
OR
I2C cmd
GPI interrupt
OR
I2C cmd I2C cmd
I2C cmd I2C cmd
Power On
I2C cmd
passive
timeout
'I2C cmd' - write to CompOpMode[1:0]
Figure 8 Operation modes
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
14
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
3.5 Sensors on the PCB
The capacitive sensors are relativel y simple copper areas on the PCB connected to the eight SX8636 capacitive
sensor input pins (CAP0…CAP7).The sensors are covered by isolating overlay material (typically 1mm...3mm).
The area of a sensor is t ypically one s quare centim eter which corr esponds abo ut to the area of a finger t ouching
the overlay material.
The capacitive sensors can be setup as ON/OFF buttons for either touch or proximity sensing (see example
Figure 9).
Figure 9 P CB t op layer of three touch buttons sensors surrounded by a proximity sensor
Please refer to the layout guidelines application note [1], for more details.
3.6 Button Information
3.6.1 Button Information
The touch buttons have two simple states (see Figure 10): ON (touched by finger) and OFF (released and no
finger press).
off on off off
Figure 10 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 tick s from the ASI go below the thresho ld minus a hysteresis. T he hysteresis around
the threshold avoids rapid touch and release signaling during transients.
Buttons c an also b e us ed t o do pr oximity sensin g. The princip le of prox imity sensing opera t ion is ex actly the sam e
as for touch buttons except that pr oximit y sensing is done s everal cent imeters ab ove th e overla y through the air.
ON state means that finger/hand is detected by the sensor and OFF state means the finger/hand is far from the
sensor.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
15
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
3.7 Analog Sensing Interface
The Analog Sensing Interface (ASI) converts the charge on the sensors into ticks which will be further digitally
processed. The bas ic pr inci ple of the ASI will be expla ined in this secti on.
The ASI cons ists of a m ultiplexer select ing the sensor , analog sw itches, a refer enc e voltage, an ADC sigma delt a
converter, an offset compensation DAC and an external integration capacitor (see Figure 11).
switches
cap2
cap1
cap0
cn
cp
analog
multi-
plexor
Offset
compensation
DAC
ADC
ticks (raw)
compensation DCV
ASI processing
Cint
voltage
reference
low pass
ticks-diff
ticks-ave
cap7
Figure 11 Analog Sensor Interface
To get the ticks representing the charge on a specific sensor the ASI will execute several steps.
The charge on a sensor ca p (e.g. C AP0) will be accu mulated m ultiple tim es on t he externa l integrat ion cap acitor,
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-up.
The difference between the DAC output and the charge on Cint is the desired signal. In the ideal case the
differ ence of charge will be c onverted t o zero tick s if no finger is pres ent and the num ber of ticks becomes 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 SX8636 allows setting the sensitivity for each sensor individually in applications which have a variety of
sensors sizes or dif fer ent overla ys or for fine-tuning pe rf orm ances. T he optim al sensitivit y is dependi ng heavil y on
the final app lication. If the sensit ivity is too lo w the ticks will n ot pass the thres holds and touc h/proxim ity detection
will not be possible. In case the sensitivity is set too large, some power will be wasted and false touch/proximity
information may be output (ie for touch buttons => finger not touching yet, for proximity sensors => finger/hand not
close enough).
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.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
16
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
The ticks from the ASI will then be handled by the digital processing.
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 oupling a n d the s ens or pl anes . T his c apacit anc e is r el ati vely large and might becom e eas ily some
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 apacitance. T his would re quire a ver y precis e, high res olution ADC a nd com plicated, pow er consum ing,
digital processing.
The SX8636 featur es a 16 bit DAC whic h compens ates f or the larg e, slo w varying c apacita nce alrea dy in fr ont 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 SX8636 the D igital Com pensation V alues (DCV) are estim ated by the digital processing
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 SX8636 is shut d own the com pensati on values will be los t. At a nex t power -up the proc edure starts all over
again. T his assures th at the SX8636 w ill operate und er any condit ion. Powering up at e.g. dif ferent temper atures
will not change the performance of the SX8636 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 SX8636 will initiate a compensation procedure
and find a new set of DCVs.
Compensation procedures can as well be initiated by the SX8636 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 can initiat e a compens ation proced ure b y using the I2C interf ace (in Acti ve or D o ze m ode) . T h is is
e.g. required after the host changed the sensitivity of sensors.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
17
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
3.9 Processing
The fir st proc essing step of the raw tick s, c oming out o f the ASI, is low p ass f iltering to o btain an estim ation of th e
average capacitance: tick-ave (see Figure 12).
This slowly varying average is important in the detection of slowly changing environmental changes.
ticks (raw)
compensation DCV
ASI processing
low pass
tick-diff
tick-ave
processing
GPIO
controller
PWM LED
controller
I2C
SPM
Figure 12 Processing
The difference of the tick average and the raw ticks, tick-diff, is a good estimation of rapid changing input
capacitances.
The tick-diff, tick-ave and the c onf ig urati on par ameters in t he SPM are then pr oc ess ed an d d eter mines the sensor
information, I2C registers status and PWM control.
3.10 Configuration
Figure 13 shows the building blocks used for configuring the SX8636.
micro
processor
MTP
NVM
I2C
SX8636
HOST
SPM QSM
Figure 13 Configuration
The default configuration parameters of the SX8636 are stored in the Quick Start Memory (QSM). This
configuration data is setup to a very common application for the SX8636 with eight buttons. Without any
programming or host interaction the SX8636 will startup in the Quick Start Application.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
18
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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 SX8636 can be setup and/or
programmed over the I2C interface.
The configuration parameters of the SX8636 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 SX8636 checks if the NVM contains valid data. In that case the configuration parameter source
becom es the NV M. If the N VM is em pt y or non-va lid t hen t he co nfigurat ion s ource becom es t he QSM. In t he nex t
step the SX8636 copies the configuration parameter source (QSM or N VM) into the Shadow Param eter Memory
(SPM). The SX8636 is operational and uses the configuration parameters of the SPM.
During p o wer do wn or res e t e vent th e SPM los es a ll c onte nt. It wil l a utomaticall y be r e loaded (fr om Q SM or NVM)
following power up or at the end of the reset event.
The host will interface with the SX8636 through the I2C bus.
The I2C of the SX8636 consists of 16 registers. Some of these I2C registers are used to read the status and
information of the button. Other I2C registers allow the host to take control of the SX8636. 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 14 shows the Host SPM mode. In this mode the host can decide to overwrite the SPM. This is useful
during the d evelo pment phases of the application wher e the c onf igurat io n par ameters ar e not yet ful ly def ine d and
as well during the operation of the application if some parameters need to be changed d ynamicall y.
micro
processor
MTP
NVM
I2C
SX8636
HOST
SPM
Figure 14 Host SPM mode
The cont ent of the S PM re mains valid as lon g as the SX8636 is po wer ed a nd no r eset is performed. After a po wer
down or reset the host needs to re-write the SPM if relevant for the application.
Figure 15 shows the Host NVM mode. In this mode the host will be able to write the NVM.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
19
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
micro
processor
MTP
NVM
I2C
SX8636
HOST
SPM
1
2
Figure 15 Host NVM mode
The writing of the host towards the NVM is not done dir ec tl y but done in 2 steps (Figure 15).
In the first step the host writes to the SPM (as in Figure 14). In the second step the host signals the SX8636 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 written t o the NVM over the I2C using the 2 steps a pproach 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 SX8636 uses on-chip voltage regulators which are controlled by the on-chip microprocessor. The regulators
need to be stabilized with an external capacitor between VANA and ground and bet ween VDIG and ground (see
Table 5). Both regulators are designed to only drive the SX8636 internal circuitry and must not be loaded
externally.
3.12 Clock Circuitry
The SX8636 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 SX8636.
The I2C slave implemented on the SX8636 is compliant with the standard (100kb/s) and fast mode (400kb/s)
The default SX8636 I2C address equals 0b010 1011.
A different I2C address can be programmed by the user in the NVM.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
20
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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 SX8636 is then ready for operation.
VDD
INTB
time
VDD
t por
supply
voltage
VDDmin
time
SX8636 ready
Figure 16 Pow er Up vs. INTB
During the po wer on p er iod t he SX8636 stabi li zes th e i nter na l reg ula tor s, RC c loc k s and the f irmware init ial i zes all
registers.
During the power up the SX8636 is not accessible and I2C communications are forbidden.
As soon as the INTB rises the SX8636 will be ready for I2C communication.
3.14.2 RESETB
When RESETB is driven low the SX8636 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.
VDD
t res
RESETB
time
SX8636 startup
VDD
INTB
time
t por
SX8636 ready
Figure 17 Hardware Reset
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
21
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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.
SoftReset
register
time
SX8636 startup
VDD
INTB
time
t
por
SX8636 ready
0xDE 0x00
Figure 18 Sof t ware Reset
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
22
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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 SX8636 is then ready for operation.
VDD
INTB
time
VDD
t por
supply
voltage
VDDmin
time
SX8636 ready
Figure 19 Pow er Up vs. INTB
During the po wer on p er iod t he SX8636 stabi li zes th e i nter na l reg ula tor s, RC c loc k s and the f irmware init ial i zes all
registers.
During the power up the SX8636 is not accessible and I2C communications are forbidden.
As soon as the INTB rises the SX8636 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 event occurred (touch or r elease if enabled ). I2C register Cap StatLsb sho w the detailed status of
the Buttons,
• if a GPI edge occ urred (rising or falling if enab led). I2C register 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.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
23
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
3.15.4 Example
A typical example of the assertion and clearing of the INTB and the I2C communication is shown in Figure 20.
off on on off
INTB
time
I2C
1
2
3
4
read read
Figure 20 I nt errupt and I2C
When a button is touched the SX8636 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 r eleases the bu tton the inter ru pt will be as s er ted ( 3). The host reading the Ir qSrc inf ormation will c lear
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 SX8636 off er s eight Genera l Pur pos e Inp ut a nd O utputs (G PIO) p ins which c an be c o nf igured in any of thes e
modes:
- GPI (General Purpose Input)
- GPP (General Pur p ose P WM)
- 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 defined as in f igure below, driving an LED as exam ple. It has to be set
accordingly in SPM parameter GpioPolarity.
gpio
gpio
vdd
(a) (b)
Figure 21 Po lar it y definition, (a) normal, (b) inverted
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
24
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
The PWM blocks used in GPP and GPO modes are 8-bits based and clocked at 2MHz typ. hence offering 256
selectab le puls e width va lues with a granularity of 128us typ.
time
VDD
(a)
period
width
time
VDD
(b)
period
width
Figure 22 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
SPM
GpioMode
X
GpioPullUpDown
X
GpioInterrupt
X
GpioDebounce
X
I2C
IrqSrc[4]
X
GpiStat
X
Table 7 SPM/I2C Param eters 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 dimm ing.
Typical GPP operation is illustrated in figure below.
I2C
0% 50% 100%
SX8636HOST SX8636HOST
GppIntensity = 0x7F
I2C
GppIntensity = 0xFF
Figure 23 LED control 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.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
25
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
GPP
SPM
GpioMode
X
GpioOutPwrUp
X1
GpioPolarity
X
GpioIntensityOn
X1
GpioIntensityOff
X1
GpioFunction
X
I2C
GppPinId
X
GppIntensity
X1
1 At power up, GppIntensity of each GPP pin is initialized with GpioIntensityOn or Gpi oIntensityOff depending on GpioOutPwrUp
corresponding bits value.
Table 8 SPM/I2C Param eters 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. Typical 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.
I2C
OFF ON OFF
SX8636HOST SX8636HOST
GpoCtrl = 1
I2C
GpoCtrl = 0
Figure 24 LED Control in GPO mode, Autolight O FF
OFF ON OFF
Figure 25 LED Control in GPO mode, Autolight ON (mapped to Button)
Addition ally these tra nsitions c an be configured to be done with or without fadin g following a logarithm ic or linear
function. This is illustrated in figures below.
time
PWM pulse width
intensity ON
intensity OFF
fading steps
inc. time
time
intensity ON
intensity OFF
fading steps
inc. time
(a) (b)
trigger trigger
PWM pulse width
Figure 26 G PO O N transition (LED fade in), normal polarity, (a) linear, (b) logarithmic
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
26
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
time
intensity ON
intensity OFF
fading steps
inc. time
time
intensity ON
intensity OFF
fading steps
inc. time
(a) (b)
trigger trigger
PWM pulse width
PWM pulse width
Figure 27 G PO O N transition (LED fade in), inverted polarity, (a) linear, (b) logarithmic
The fading o ut (e.g. af ter a button is release d) is ident ical to the f ading in bu t an addit ional off delay can b e added
before the fading starts (Figure 28 and Figure 29).
intensity OFF
intensity ON
fading steps
dec. time
trigger time time
intensity OFF
intensity ON
fading steps
(b)
trigger
off delay
dec. time
off delay
PWM pulse width
PWM pulse width
Figure 28 G PO O FF transition (LED fade out), normal polarity, (a) linear, (b) logarithmic
time
intensity OFF
intensity ON
fading steps
dec. time
(a)
trigger time
intensity OFF
intensity ON
fading steps
dec. time
(b)
trigger
off delay
off delay
PWM pulse width
PWM pulse width
Figure 29 G PO O FF transition (LED fade out), inverted polarity, (a) linear, (b) logarithmic
Please n ote tha t stan dard high/l ow log ic sig nals are ju st a spec ific c ase of G PO m ode and c an a lso be g ener ated
simply by setting inc/dec time to 0 (ie OFF) and programming intensity OFF/ON to 0x00 and 0xFF.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
27
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
SPM/I2C parameters applicable in GPO mode are listed in table below.
GPO
SPM
GpioMode
X
GpioOutPwrUp
X1
GpioAutoligth
X
GpioPolarity
X
GpioIntensityOn
X
GpioIntensityOff
X
GpioFunction
X
GpioIncFactor
X
GpioDecFactor
X
GpioIncTime
X
GpioDecTime
X
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 Param eters Applicable in GPO Mode
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
28
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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 width (normal polarity)
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 Int ens ity 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).
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
29
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
3.17 Smart Wake Up
The SX8636 off ers a sm art wake up m echanism (up t o 6 ke ys) which al lows wak ing-up from the Do ze low po wer
mode to the Active mode in a secure/controlled way and not by any unintentional sensor activation.
Until t he full correct wake-up s equence is enter ed, the SX863 6 will remain in Doze mode. An y wrong ke y implies
the whole sequence to be entered again.
Please note that each key touch must be followed by a release to be validated.
Hence if a proximity sensor and a touch button part of the wake-up sequence are interleaved on the PCB (ie if you
cannot touch the button without triggering proximity detection) the smart wake up feature cannot be used since
the proximity sensor is not “released” before the buttons are touched. In this case the smart wakeup sequence
must be turned OFF.
The smart wake-up mechanism can also be disabled which implies that Doze mode can hence only be exited
from GPI or I2C command.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
30
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
4 PIN DESCRIPTIONS
4.1 Introduction
This chapter describes briefly the pins of the SX8636, 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 30 shows the simplified diagram of the CAP0, CAP1, ..., CAP7 pins.
SX8636
sensor
ASI
CAPx
CAP_INx
VANA
Note : x = 0, 1,2,…7
Figure 30 S im plified diagram of CAP0, CAP1, ..., CAP7
CN, CP
The CN and the C P pins are connec ted to th e ASI circuitr y. A 1nF sam plin g capa citor bet ween CP an d CN n eeds
to be placed as close as possible to the SX8636.
The CN and CP are protected to VANA and GROUND.
Figure 31 shows the simplified diagram of the CN and CP pins.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
31
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
SX8636
ASI
CP
VANA
CN
VANA
Figure 31 S im plified 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 32 shows a simplified diagram of the INTB pin.
VDD
R_INT
INTB
SX8636
INT
to host
Figure 32 S im plified diagram of INTB
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
32
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
SCL
The SCL pi n is a high impedance input pin. T he SCL pin is pro tec ted to V D D, us in g de dica ted devices , in 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 33 shows the simplified diagram of the SCL pin.
VDD
R_SCL
SCL
SX8636
from host
SCL_IN
Figure 33 S im plified 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 34 shows the simplified diagram of the SDA pin.
VDD
R_SDA
SDA
SX8636
SDA_OUT
from/to host
SDA_IN
Figure 34 S im plified diagram of SDA
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
33
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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 35 shows the simplified diagram of the RESETB pin controlled by the host.
VDD
R_RESETB
RESETB
SX8636
from host
RESETB_IN
Figure 35 S im plified diagram of RESETB controlled by host
Figure 36 shows the RESETB without host control.
VDD
RESETB
SX8636
RESETB_IN
Figure 36 S im plified diagram of RESETB without host control
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
34
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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 SX8636.
VDD has protection to GROUND.
Figure 37 shows a simplified diagram of the VDD pin.
VDD
SX8636
VDD
Figure 37 S im plified diagram of VDD
GND
The SX8636 has four grou nd pins al l nam ed GND. T hese pins and the pac k age center pa d need to b e conn ected
to ground pot ent ial .
The GND has protection to VDD.
Figure 38 shows a simplified diagram of the GND pin.
VDD
SX8636
GND
GND
Figure 38 S im plified diagram of GND
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
35
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
VANA, V DIG
The SX8636 has on-chip regulators for internal use (pins VAN A 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 39 shows a simplified diagram of the VANA and VDIG pin.
VDD
SX8636
GND
VDIG
VDD
GND
VANA
VANA
VDIG
Cvdig
Cvana
Figure 39 S im plified diagram of VANA and VDIG
4.5 General purpose IO pins
The SX8636 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 40 shows a simplified diagram of the GPIO pins.
SX8636
VDD Rup
ctrl
Rdown
GPIO7...0
ctrl
GPO,
GPP
VDD
PWM
GPI
GPO,
GPP
VDD
Figure 40 S im plified diagram of GPIO pins
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
36
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
5 DETAILED CONFIGURATION DESCRIPTIONS
5.1 Introduction
The SX8636 configuration parameters ar e taken from the QSM or the NVM and l oade d i nto th e S PM as exp l ain ed
in the chapter ‘functional description’.
This chapter describes the details of the configuration parameters of the SX8636.
.
The SPM is split by functionality into 5 configuration sections:
• General section: operating modes,
• Capaciti ve Sens or s section: related to lower level capacitive sensing,
• Button: related to the conversion from sensor data towards button information,
• Mapping: related to mapping of button 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).
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
37
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
Address Name default QSM
value Address Name default QSM
value
0x00
Reserved
0xxx
0x20
Reserved
0x00
0x01 Reserved 0xxx 0x21
Button
BtnCfg 0x30
0x02 Reserved 0x21 0x22 BtnAvgThresh 0x50
0x03 Reserved 0xxx 0x23 BtnCompNegThresh 0x50
0x04
General
I2CAddress
0x2B
0x24
BtnCompNegCntMax
0x01
0x05
ActiveScanPeriod
0x02
0x25
BtnHysteresis
0x0A
0x06 DozeScanPeriod 0x0D 0x26 BtnStuckAtTimeout 0x00
0x07 PassiveTimer 0x00 0x27 Reserved 0x00
0x08 Reserved 0x00 0x28 Reserved 0x00
0x09
Capacitive Sensors
CapModeMisc 0x01 0x29 Reserved 0x00
0x0A
Reserved
0x00
0x2A
Reserved
0xFF
0x0B CapMode7_4 0x55 0x2B Reserved 0x00
0x0C CapMode3_0 0x55 0x2C Reserved 0x00
0x0D CapSensitivity0_1 0x00 0x2D Reserved 0x00
0x0E CapSensitivity2_3 0x00 0x2E Reserved 0x00
0x0F
CapSensitivity4_5
0x00
0x2F
Reserved
0x00
0x10 CapSensitivity6_7 0x00 0x30 Reserved 0x00
0x11 Reserved 0x00 0x31 Reserved 0x00
0x12 Reserved 0x00 0x32 Reserved 0x00
0x13
CapThresh0
0xA0
0x33
Mapping
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 0x76
0x18 CapThresh5 0xA0 0x38 MapAutoLight1 0x54
0x19
CapThresh6
0xA0
0x39
MapAutoLight2
0x32
0x1A CapThresh7 0xA0 0x3A MapAutoLight3 0x10
0x1B Reserved 0xA0 0x3B MapAutoLightGrp0Msb 0x00
0x1C Reserved 0xA0 0x3C MapAutoLightGrp0Lsb 0x00
0x1D Reserved 0xA0 0x3D MapAutoLightGrp1Msb 0x00
0x1E
Reserved
0xA0
0x3E
MapAutoLightGrp1Lsb
0x00
0x1F CapPerComp 0x00 0x3F Reserved 0x00
Table 12 SPM address map: 0x00…0x3F
Note
• ‘0xxx’: write protected data
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
38
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
Address Name default QSM
value Address Name
default QSM
value
0x40
Gpio
GpioMode7_4
0x00
0x60
Gpio
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
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 CapProxEnable 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 GpioDecTime3_2 0x44 0x7F SpmCrc* 0xD0
Table 13 SPM address map: 0x40…0x7F
Note*
• SpmCrc: CRC depending on SPM content, updated in Active or Doze mode.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
39
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
5.2 General Parameters
General Parameters
Address Name Bits Description
0x04
I2CAddress
7
Reserved
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 Information (Figure 8)
0x00: OFF (default)
0x01: 1 second
…
0xFF: 255 seconds
Table 14 Gener al Param eter s
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
40
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
5.3 Capacitive Sensors Parameters
Capacitive Sensors Parameters
Address Name Bits Description
0x09
CapModeMisc
7:3
Reserved
2:0
IndividualSensitivity
Defines common sensitivity for all sensors or individual
sensor sen si tiv i ty .
001: Common settings (CapSensitivity0_1[7:4])
100: Individual CAP sensitivity settings (CapSensitivityx_x)
Else : Reserved
0x0A
Reserved
7:0
Reserved
0x0B
CapMode7_4
7:6
CAP7 Mode
Defines the mode of
the CAP pin.
00: Disabled
01: Button
10: Reserved
11: Reserved
Default
Button
5:4
CAP6 Mode
Button
3:2
CAP5 Mode
Button
1:0
CAP4 Mode
Button
0x0C
CapMode3_0
7:6
CAP3 Mode
Button
5:4
CAP2 Mode
Button
3:2
CAP1 Mode
Button
1:0
CAP0 Mode
Button
0x0D
CapSensitivity0_1
7:4
CAP0 Sensitivity - Common Sensitivity
Defines the sensitivity.
0x0: Minimum (default)
0x7: Maximum
0x8…0xF: Reserved
3:0
CAP1 Sensitivity
0x0E
CapSensitivity2_3
7:4
CAP2 Sensitivity
3:0
CAP3 Sensitivity
0x0F
CapSensitivity4_5
7:4
CAP4 Sensitivity
3:0
CAP5 Sensitivity
0x10
CapSensitivity6_7
7:4
CAP6 Sensitivity
3:0
CAP7 Sensitivity
0x11
Reserved
7:0
Reserved
0x12
Reserved
7:0
Reserved
0x13
CapThresh0
7:0
CAP0 Touch Threshold
Defines the Touch Threshold ticks.
0x00: 0,
0x01: 4,
…
0xA0: 640 (default),
…
0xFF: 1020
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
0x1B
Reserved
7:0
Reserved
0x1C
Reserved
7:0
Reserved
0x1D
Reserved
7:0
Reserved
0x1E
Reserved
7:0
Reserved
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
41
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
Capacitive Sensors Parameters
Address Name Bits Description
0x1F
CapPerComp
7:4
Reserved
3:0
Periodic Offset Compensation
Defines the period ic offs et co mpen sat ion.
0x0: OFF (default)
0x1: 1 second
0x2: 2 seconds
…
0x7: 7 seconds
0x8: 16 seconds
0x9: 18 seconds
…
0xE: 28 seconds
0xF: 60 seconds
0x70
CapProxEnable
7:0
Enables proximity sensing:
0x46: OFF
0x74: ON
Table 15 Capacitive Sensors Parameters
CapModeMisc
By default th e A SI is us in g a c om m on s ensitiv ity for all capac iti ve sens ors as in t h e usual c as e o verl a y m aterial
and sensors sizes are about equal. The register bits CapSensitivity0_1[7:4] determine the sensitivity for all
sensors in common sensitivity mode.
It might be required to have a different, individual, sensitivity for each CAP pin (for example proximity sensor
set to max sensitivity while touch sensors are set to a lower one). This can be obtained by setting
CapModeMisc[2:0] to “100” 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 or disabled depending on the application.
minimum default maximum
buttons one eight eight
Table 16 Possible CAP pin modes
Buttons and disabled CAP pins can be attributed freely (examples in Figure 41). All buttons can be used for
touch or proximity sensing, in the latter case register CapProxEnable needs to be set accordingly.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
42
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
SX8636
cap1 (button1)
cap4 (disabled)
cap2 (button2)
cap3 (button3)
cap5 (disabled)
cap6 (disabled)
SX8636
cap1 (button1)
cap6 (button6)
cap3 (button3)
cap2 (disabled)
cap4 (disabled)
cap5 (disabled)
Figure 41 Button examples
CapSensitivity0_1, CapSensitivity2_3, CapSensitivity4_5, CapSensitivity6_7, CapProxEnable:
The sens itivity of the sens ors c an be s et bet ween 8 va l ues. T he higher the sensit iv ity is set the lar g er the v al 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 or proximity sensing.
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 touch sensors.
The sens itivit y is ident ical f or al l sensor s in c omm on sensit ivit y mode us ing the bits C apSensit i vity0_1[7 :4] and
can be set individually using register CapModeMisc[2:0].
The maximum number of ticks that can be obtained depends on the selected sensitivity and if proximity
sensing is enabled. This is illustrated in Table 17.
Sensitivity Approximate
Maximum Tick Level
(CapPr o xEnable = OFF)
Approximate
Maximum Tick Level
(CapPr o xEnable = ON)
0
1000
4000
1
2000
8000
2
3000
12000
3
4000
16000
4
5000
20000
5
6000
24000
6
7000
28000
7
8000
32000
Table 17 ASI Maximum Tick Levels
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
43
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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 SX8636 for making touch and release decisions on e.g. touch or no-
touch.
The details are explained in the sections for buttons.
CapPerComp:
The SX8636 offers a periodic offset compensation for applications which are subject to substantial
environm ental changes. The period ic offset com pensation is done at a defined interval and onl y if buttons are
released.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
44
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
5.4 Button Parameters
Button Parameters
Address Name Bits Description
0x21
BtnCfg
7:6
Defines the buttons events reporting method.
00: Multiple reporting of all tou che s 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 sample (defau lt)
01: 2 samples debounce
10: 3 samples debounce
11: 4 samples debounce
1:0
Defines the number of samples at the scan period for determining a touch
00: OFF, use incoming sample (defau lt)
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 negativ e offs et co mpen sat ion thr e shold.
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 (def ault )
…
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)
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
45
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
Button Parameters
Address Name Bits Description
0x01: 1 second
…
0xFF: 255 seconds
Table 18 Butt on Conf iguration Parameters
Please not e th at pr oximity s ens ors are c o nf igur ed as buttons a nd operate ex actl y t he s ame wa y as touch b uttons.
All the parameters and procedures described below apply similarly.
A reliable button operation requires a coherent setting of the registers.
Figure 42 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.
time
0
ticks_diff
BtnHysteresis
BtnHysteresis
= no-touch
Touch
(touch debounce = 1)
= touch
(release debounce = 0)
Release
CapThreshold
= scan events @ scan period
Figure 42 Touc h 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 42 the touch is validated after 2 samples (BtnCfg [1:0 ] = 01).
The releas e is detec ted im m ediatel y (BtnCfg [3:2] = 00) at the f irst sample whic h is bel ow the t hresh old m inus the
hysteresis.
BtnCfg
The SX8636 can re por t a ll touc hes of multiple fing ers o r the SX8636 can be set to report on l y the f irs t 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 SX8636 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.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
46
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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
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 SX8636 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 43.
time
0
ticks_diff
CompNegCnt = 1, 2,...
CompNegThreshold
= ticks < CompNegThreshold
= ticks, no-touch
offset
compensation
CompNegCnt > CompNegCntMax
Figure 43 Negative Ticks O ff set 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 rec omm ended valu e for this regis ter is ‘ 1’ which m eans that th e off set c ompens ation star ts on the firs t 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.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
47
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
If the stuckat timer is set to one second then the touch of a finger will last only for one second and then a
compensation will be performed and button hence considered released, even if the finger remains on the
button f or a l ong er time. After the act ua l f inger re le as e the b utton can be t ouched aga in a nd wil l be r ep or ted as
usual.
In case the stuckat timer is not required it can be set to zero.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
48
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
5.5 Mapping Parameters
Mapping Parameters
Address Name Bits Description
0x33
MapWakeupSize
7:3
Reserved
2:0
Doze -> Active wake up sequence size.
0: Any sensor event (default)
1: key0
2: key0, key1
…
6: key0, key1, … key 5
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.
0x34
MapWakeupValue0
7:4
key5
Defines the sensor event associated to each key.
0x00: Btn0 (default)
0x01: Btn1
…
0x07: Btn7
0x08…0x0F: Reserved
3:0
key4
0x35
MapWakeupValue1
7:4
key3
3:0
key2
0x36
MapWakeupValue2
7:4
key1
3:0
key0
0x37
MapAutoLight0
7:4
GPIO[7]
Defines the mapping between GPOs (with
Autolight ON) and sensor events.
0x00: Btn0 (default)
0x01: Btn1
…
0x07: Btn7
0x08…0x0B: Reserved
0x0C: Group0 as defi ned by MapAutoLightGrp0
0x0D: Group1 as defined by MapAutoLightGrp1
0x0E: Reserved
0x0F: Reserved
Several GPOs can be mapped to the same
sensor
event and will be controlled simultaneously.
3:0
GPIO[6]
0x38
MapAutoLight1
7:4
GPIO[5]
3:0
GPIO[4]
0x39
MapAutoLight2
7:4
GPIO[3]
3:0
GPIO[2]
0x3A
MapAutoLight3
7:4
GPIO[1]
3:0
GPIO[0]
0x3B
MapAutoLightGrp0Msb
7:0
Reserved
0x3C
MapAutoLightGrp0Lsb
7
Btn7
Defines Group0 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.
6
Btn6
5
Btn5
4
Btn4
3
Btn3
2
Btn2
1
Btn1
0
Btn0
0x3D
MapAutoLightGrp1Msb
7:0
Reserved
0x3E
MapAutoLightGrp1Lsb
7
Btn7
Defines Group1 sensor events:
0: OFF (default)
1: ON
6
Btn6
5
Btn5
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
49
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
Mapping Parameters
Address Name Bits Description
4
Btn4
If any of the enabled sensor events occurs the
Group0 event will occur as well.
All sensors events w
ithin the group can be
independently set.
3
Btn3
2
Btn2
1
Btn1
0
Btn0
Table 19 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 si ze is set to 6 t hen wak eup is don e onl y by GPI or an I2C c omm and (ma y be required if proxim ity sensing
is enable, see §3.17 for more details).
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
MapAutoLight0, MapAutoLight1, MapAutoLight2, MapAutoLight3
MapAutoLightGrp0Msb, MapAutoLightGrp0Lsb, MapAutoLightGrp1Msb, MapAutoLightGrp1Lsb
These r egist ers d ef ine the mapping between the G PO pi ns (with Autolight ON) and the s e ns or i nf ormation whic h
will control its ON/OFF state.
The mapping can be done to a specific sensor event but also o n groups (in this case any sensor event in the
group will control the GPO).
Table 20 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
Table 20 Autolight Mapping, Sensor Information
Examples:
- If GPO[0] should change state accordi ng l y 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)
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
50
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
5.6 GPIO Parameters
GPIO Parameters
Address Name Bits Description
0x40
GpioMode7_4
7:6
GPIO[7] Mode
Defines the GPIO mode.
00: GPO (default)
01: GPP
10: GPI
11: Reserved
5:4
GPIO[6] Mode
3:2
GPIO[5] Mode
1:0
GPIO[4] Mode
0x41
GpioMode3_0
7:6
GPIO[3] Mode
5:4
GPIO[2] Mode
3:2
GPIO[1] Mode
1:0
GPIO[0] Mode
0x42
GpioOutPwrUp
7:0
GPIO[7] 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 w ith pull 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
GPIO[0] Output Value at Power Up
0x43
GpioAutoLight
7:0
GPIO[7] AutoLight
Enables Autolight in GPO mode
0 : OFF
1 : ON (default)
GPIO[6] AutoLight
GPIO[5] AutoLight
GPIO[4] AutoLight
GPIO[3] AutoLight
GPIO[2] AutoLight
GPIO[1] AutoLight
GPIO[0] AutoLight
0x44
GpioPolarity
7:0
GPIO[7] Output Polarity
Defines the polarity of the GPO and GPP
pins.
0: Inverted (default)
1: Normal
GPIO[6] Output Polarity
GPIO[5] Output Polarity
GPIO[4] Output Polarity
GPIO[3] Output Polarity
GPIO[2] Output Polarity
GPIO[1] Output Polarity
GPIO[0] Output Polarity
0x45
GpioIntensityOn0
7:0
ON Intensity Index
Defines the ON intensity index
0x00: 0
0x01: 1
0x46
GpioIntensityOn1
0x47
GpioIntensityOn2
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
51
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
GPIO Parameters
Address Name Bits Description
0x48
GpioIntensityOn3
…
0xFF: 255 (default)
0x49
GpioIntensityOn4
0x4A
GpioIntensityOn5
0x4B
GpioIntensityOn6
0x4C
GpioIntensityOn7
0x4D
GpioIntensityOff0
7:0
OFF Intensity Index
Defines the OFF inte nsity ind ex
0x00: 0 (default)
0x01: 1
…
0xFF: 255
0x4E
GpioIntensityOff1
0x4F
GpioIntensityOff2
0x50
GpioIntensityOff3
0x51
GpioIntensityOff4
0x52
GpioIntensityOff5
0x53
GpioIntensityOff6
0x54
GpioIntensityOff7
0x56
GpioFunction
7:0
GPIO[7] Function
Defines the intens ity index vs PWM pulse
width function.
0: Logarithmic (default)
1: Linear
GPIO[6] Function
GPIO[5] Function
GPIO[4] Function
GPIO[3] Function
GPIO[2] Function
GPIO[1] Function
GPIO[0] Function
0x57
GpioIncFactor
7:0
GPIO[7] Fading Increment Factor
Defines the fading increment f actor .
0: 1, intensity index incremented every
increment time (default)
1: 16, intensity index incremented every 16
increment times
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
GPIO[0] Fading Increment Factor
0x58
GpioDecFactor
7:0
GPIO[7] 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
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
GPIO[0] Fading Decrement Factor
0x59
GpioIncTime7_6
7:4
GPIO[7] Fading Increment Time
Defines the fading increment time.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
52
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
GPIO Parameters
Address Name Bits Description
3:0
GPIO[6] 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)
0x5A
GpioIncTime5_4
7:4
GPIO[5] Fading Increment Time
3:0
GPIO[4] Fading Increment Time
0x5B
GpioIncTime3_2
7:4
GPIO[3] Fading Increment Time
3:0
GPIO[2] Fading Increment Time
0x5C
GpioIncTime1_0
7:4
GPIO[1] Fading Increment Time
3:0
GPIO[0] Fading Increment Time
0x5D
GpioDecTime7_6
7:4
GPIO[7] 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)
3:0
GPIO[6] Fading Decrement Time
0x5E
GpioDecTime5_4
7:4
GPIO[5] Fading Decrement Time
3:0
GPIO[4] Fading Decrement Time
0x5F
GpioDecTime3_2
7:4
GPIO[3] Fading Decrement Time
3:0
GPIO[2] Fading Decrement Time
0x60
GpioDecTime1_0
7:4
GPIO[1] Fading Decrement Time
3:0
GPIO[0] Fading Decrement Time
0x61
GpioOffDelay7_6
7:4
GPIO[7] OFF Delay
Defines the delay after GPO OFF trigge r
before fading out starts.
0x0: OFF (default)
0x1: 200ms
0x2: 400ms
…
0xF: 3000ms
3:0
GPIO[6] OFF Delay
0x62
GpioOffDelay5_4
7:4
GPIO[5] OFF Delay
3:0
GPIO[4] OFF Delay
0x63
GpioOffDelay3_2
7:4
GPIO[3] OFF Delay
3:0
GPIO[2] OFF Delay
0x64
GpioOffDelay1_0
7:4
GPIO[1] OFF Delay
3:0
GPIO[0] OFF Delay
0x65
GpioPullUpDown7_4
7:6
GPIO[7] Pullup/down
Enables pullup/down resistors for GPI pins.
00 : None (default)
01 : Pullup
10 : Pulldown
11 : Reserved
5:4
GPIO[6] Pullup/down
3:2
GPIO[5] Pullup/down
1:0
GPIO[4] Pullup/down
0x66
GpioPullUpDown3_0
7:6
GPIO[3] Pullup/down
5:4
GPIO[2] Pullup/down
3:2
GPIO[1] Pullup/down
1:0
GPIO[0] Pullup/down
0x67
GpioInterrupt7_4
7:6
GPI[7] 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
5:4
GPI[6] Interrupt
3:2
GPI[5] Interrupt
1:0
GPI[4] Interrupt
0x68
GpioInterrupt3_0
7:6
GPI[3] Interrupt
5:4
GPI[2] Interrupt
3:2
GPI[1] Interrupt
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
53
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
GPIO Parameters
Address Name Bits Description
1:0
GPI[0] Interrupt
0x69
GpioDebounce
7:0
GPI[7] Debounce
Enables the GPI debounce (done on 10
consecutiv e sample s at 1ms).
0 : OFF (default)
1 : ON
GPI[6] Debounce
GPI[5] Debounce
GPI[4] Debounce
GPI[3] Debounce
GPI[2] Debounce
GPI[1] Debounce
GPI[0] Debounce
Table 21 GPIO Parameters
Table 22 resumes the applicable SPM and I2C parameters for each GPIO mode.
GPI
GPP
GPO
SPM
GpioMode
X
X
X
GpioOutPwrUp
X1
X2
GpioAutoligth
X
GpioPolarity
X
X
GpioIntensityOn
X1
X
GpioIntensityOff
X1
X
GpioFunction
X
X
GpioIncFactor
X
GpioDecFactor
X
GpioIncTime
X
GpioDecTime
X
GpioOffDelay
X
GpioPullUpDown
X
GpioInterrupt
X
GpioDebounce
X
I2C
IrqSrc[4]
X
GpiStat
X
GpoCtrl
X3
GppPinId
X
GppIntensity
X1
1 At power up, GppIntensity of each GPP pin is initialized with GpioIntensityOn or GpioIntensityOff depending on GpioOutPwrUp
corresponding bits value.
2 Only if Autolight is O F F, els e m ust be left to 0 (default value)
3 Only if Autolight is O FF, else ignored
Table 22 Applicable SPM/I2C Parameters vs. GPIO Mode
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
54
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
6 I2C INTERFACE
The I2C implemented on the SX8636 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
processing phase (section 3.3).
Three types of registers are considered:
- status ( read) . T hes e r e gis ter s give infor mation about the stat us of the c apac itive buttons , GPIs, op er ati on 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 SX8636 is powered down.
The SPM c an be stored p ermanentl y in the NVM m emory of the SX8636. T he SPM gatewa y communic ation over
the I2C at power up is then not required.
The I2C will be able to read and write from a start address and then perform read or writes sequentially, 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 44.
After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The
SX8636 the n Acknowledge s [A] that it is being a ddressed, and the M aster sends an 8 bit D ata Byte consist ing of
the SX8636 Re gister Ad dress ( RA). The Slave Acknowled ges [ A] a nd t he mast er s ends th e a ppropriate 8 bit Dat a
Byte (W D0). Again the Slave Ack nowledges [A]. In c ase the m aster needs to write m ore data, a succeedin g 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].
SSA 0 RAA A WD0 A WD1 A WDn A P
optional optional
S: Start condition
SA: Slave Address
A: Acknowledge
RA: Register Address
WDn: Write Data byte (0...n)
P: Stop condition
from master to slave
from slave to master
Figure 44 I2C wr ite
The regis ter addres s is incr emented aut omaticall y when s uccessive re gister data (W D1...W Dn) is suppl ied by th e
master.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
55
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
6.2 I2C read
The format of the I2C read is given in Figure 45.
After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The
SX8636 t hen Ack nowledges [A] that i t is be ing addres sed, a nd the M aster respo nds with an 8 bit Data co nsisting
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 SX8636 resp onds with an Ack nowledge [A] and the read Dat a byte (RD 0). If the mas ter needs to read m ore
data it will acknowledge [A] and the SX8636 will send the next read byte (RD1). T his sequence can be repeated
until the master terminates with a NACK [N] followed by a stop [P].
S SA 0 RA
AASr N
S: Start condition
SA: Slave Address
Sr:Repeated Start condition
A:Acknowledge
N: Not Acknowledge (terminating read stream)
RA: Register Address
RDn: Read Data byte (0...n)
P: Stop condition
from master to slave
from slave to master
RD0 A
optional
SA 1ARD1
optional
RDnA P
Figure 45 I2C read
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
56
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
6.3 I2C Registers Overview
Address Name R/W Description
0x00 IrqSrc read Interrupt Source
0x01 Reserved
0x02 CapStatLsb read Button Status LSB
0x03 Reserved
0x04 Reserved
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 23 I2 C Re gis ters Overview
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
57
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
6.4 Status Registers
Address Name Bits Description
0x00 IrqSrc
7 Reserved
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.
6 NVM burn interrupt flag
5
SPM write interrupt flag
4 GPI interrupt flag
3 Reserved
2 Buttons interrupt flag
1 Compensation interrupt flag
0 Operating Mode interrupt flag
Table 24 Int er rupt 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[2] is set if a Button even t oc cur r ed (touc h or r ele as e if enabl ed). Cap Sta tLsb sho w the det aile d s tatus 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 actually enteri ng Active or Doze m ode either through aut omatic wakeup or vi a host request.
CompOpmode shows the current operation mode.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
58
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
Address Name Bits Description
0x02 CapStatLsb
7 Button 7 Touched
Button Touch statu s
0: Released (default)
1: 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
0 Button 0 Touched
Table 25, Button status 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 26 I2C GPI status
Address Name Bits Description
0x08 SpmStat
7:4 reserved
3 NvmValid
Indicates if the current NVM is valid.
0: No – QSM is used
1: Yes – NVM is used
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 us ed
Table 27 I2C SPM status
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
59
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
6.5 Control Registers
Address Name Bits Description
0x09 CompOpMode
7:3
Reserved*, write only ‘00000’
2 Compensation Indi cate s/tr i gger s com pen sati o n pro cedur e
0: Compensation completed (default)
1: read -> compensation running ; write -> trigger
compensation
1:0 Operating Mode
Indicates/programs** operating mode
00: Active mode (default)
01: Doze mode
10: Sleep mode
11: Reserved
Table 28 I2C compensation, operation modes
* The reading of these reserved bits will return varying va lues.
** 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 29 I2C GPO Control
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
60
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
Address Name Bits Description
0x0B GppPinId
7:3 Reserved, write only ‘00000’
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 30 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 Inte nsi ty O n or Inten sityOff depending on GpioOutPwrUp.
Table 31 I2C GPP Intensity
Address Name Bits Description
0xB1 SoftReset 7:0 Writing 0xDE followed by 0x00 wi ll reset the chip.
Table 32 I2C Soft Reset
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
61
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
6.6 SPM Gateway Registers
The SX8636 I2C interface offers two registers for exchanging the SPM data with the host.
• SpmCfg
• SpmBaseAddr
Address Name Bits Description
0x0D SpmCfg
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
2 Enables monitor mode (Cf. §6.8)
0: OFF
1: ON
1:0 00: Reserved
Table 33 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 34 SP M Base Ad dre s s
The exchange of data, read and write, between the host and the SPM is alway s 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 35 SPM Key MSB
Address Name Bits Description
0xAD SpmKeyLsb 7:0 SPM to NVM burn Key LSB Unlock requires writing data: 0x9D
Table 36 SPM Key LSB
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
62
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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].
SSA 00x0D
A0x10
AP
A
S : Start condition
SA : Slave address
A : Slave acknowledge
BA : NVM Base Address
WDn : Write Data byte n, n = 0 to 7
P : Stop condition
...
From master to slave
From slave to master
SSA 0 0x0EA BAA P
A
SSA 00x00
AWD0
AP
A
WD7
SSA 00x0D
A0x00A P
A
1)
2)
3)
4)
Figure 46: SPM Write Sequence
The complete SPM can be written by repeating 16 times the cycles shown in Figure 46 using base addresses
0x00, 0x08, 0x10, …, 0x70, 0x78. Between each seq uence 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.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
63
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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].
S SA 0 0x0D
A0x18
AP
A
S, Sr : Start condition
SA : Slave address
A : Slave acknowledge
N : Not Acknowledge (terminates read stream)
BA : NVM Base Address
RDn : Read Data byte n, n = 0 to 7
P : Stop condition
From master to slave
From slave to master
S SA 0 0x0E
ABAA P
A
S SA 0 0x0D
A0x00
AP
A
S
SA
SSA 0 A0x00 A Sr SA 1 ARD0 A... RD7 NP
1)
2)
3)
4)
Figure 47: SPM Read Sequenc e
The com plete SPM c an be read b y repeating 1 6 tim es the c ycles sho wn in Figure 47 us ing base a ddress es 0x00,
0x08, 0x10, …, 0x70, 0x78.
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
64
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
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
complete l y written with the des ired dat a. 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].
NVM
SPM
SpmStat[2:0] 1 2 3
0 4
QSM
Figure 48 Simplified Diagram NvmCount
Figure 48 shows the simplified diagram of the NVM counter. The SX8636 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 SX8636 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 b y 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 49.
S SA 0 0x0E
A0xA5A P
A
S : Start condition
SA : Slave address
A : Slave acknowledge
P : Stop condition
From master to slave
From slave to master
S SA 0 0x0E
A 0x5A
AP
A
3)
4)
S SA 0 0xAC
A0x62A P
A
SSA 0 0xADA 0x9D
AP
A
1)
2)
Figure 49: NVM burn procedure
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
65
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
6.8 Monitor Mode
Monitor mode allows the host to read “real-time” sensor information (CAPxRaw, CAPxAvg, CAPxDiff).
It is enabled by setting bit 2 of I2C register SpmCfg (address 0x0D).
W hen enabled, it us es a specific m onitor scan period (Cf below) and generates an interrupt ever y tim e a new full
set of data is available (hence every scan period).
Address
Name
Bits
Description
0xF9
MonitorScanPeriod
7:0
Monitor Mode Scan Period
0x00: Reserved
0x01: 15ms
…
0x0D: 195ms (default)
…
0xFF: 255 x 15ms
Monitor mode scan period is located at address 0xF9 can be written similarly as SPM data (Cf. §6.6.1).
Interrupt is cleared normally by reading I2C register IrqSrc (address 0x00) but no specific flag is set.
CAPxRaw/Avg/Diff data can be read similarly as SPM data (Cf. §6.6.2)
Base address BA = 0xB4 is the beginning of the CAPxDiff data location and data are organized this way:
0xB4: CAP0Diff, MSB
0xB5: CAP0Diff, LSB
0xB6: CAP1Diff, MSB
etc...
Values are coded 16bits signed 2's complement format and updated at each scan period.
Base address BA = 0x80 is the beginning of the CAPxRaw data location.
Base address BA = 0x9A is the beginning of the CAPxAvg data locat ion.
Data should be read before the next interrupt occurs (i.e. within one scan period).
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
66
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
7 APPLICATION INFORMATION
7.1 Typical Application Schematic
.
proximity
SX8636
cap2
cap3
cap4
cap5
cap6
cap7
gnd
gpo5
gpo4
gpo3
gpo2
gpo1
gnd
gpo0
vana
resetb
gnd
gpo7
vdig
gpo6
cn
cp
vdd
scl
intb
sda
analog
sensor
interface
micro
processor
RAM
ROM
NVM
I2C
GPIO
controller
power management
clock
generation
RC
PWM
LED
controller
bottom plate
HOST
cap0
cap1
d1
d0
d2
d3
d4
d5
d6
d7
d0
d1
d2
d3
d4
d5
d6
d7
Figure 50 Ty p ic al Application
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
67
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
7.2 Example of Touch+Proximity Module
7.2.1 Overview
To demonstrate the proximity sensing feature of the SX863x family, a module has been designed and is illustrated
in figure below.
Touch Buttons
(1.5cm pitch) Proximity Sensor
Module Size (white area) :
sensors area + SX8633 + connector (min.) Bicolor LEDs
(blue, orange) Overlay
(2mm acrylic glass)
Figure 51 Touch+Proximity Module Overview
The touch button controller is running in stand-alone (ie without host) and uses the Autolight mode to turn LEDs
ON/OFF accordingly to the touch buttons and proximity sensing status.
7.2.2 Operation
Module operation can be seen as 5 steps which are described in figure below
1. No finger
=> No proximity detected
=> All LEDs OFF
2. Finger approaches
=> Proximity detect ed
=> Blue LEDs turned ON
3. Button touch
=> Orange LED turned ON
(blue+orange = pink)
4. Button release
=> Orange LED turned
OFF
5. Finger removed
=> No proximity detected
=> Blue LEDs turned OFF
Figure 52 Touch+Proximity Module Operation
Notes:
- For better user experience, bicolor LEDs have been used here but one could decide to design a module with
normal unicolor LEDs. In this case, step 3 above would simply consist in a higher (blue) intensity for the LED of
the button touched.
- For obvious demonstration purposes the overlay used here is transparent but in typical applications (TV,
Monitor, Set-top box, etc) the overlay would be opaque enough so that when LEDs are OFF (ie no proximity
detected) the PCB is not visible to the user.
7.2.3 Performance
The proximity sensing distance of detection has been measured in these conditions:
- CapProxEnable = ON
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
68
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
- CapSensitivity = 7 (Max)
- CapThr es hold = 300
- Board main supplied and placed vertically ie same orientation as hand/finger
- Finger pointing center button
The results obtained are provided in table below:
Distance of Detection
Palm
~10cm
Finger (natural position)
~6cm
Orthogonal finger (worst case)
~4cm
Table 37 Proximity Sensing Distance of Detection
7.2.4 Schematics
Figure 53 Touch+Proximity Module Schematics
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
69
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
7.2.5 Layout
Figure 54 Touch+Proximity Module Layout - Top
Figure 55 Touch+Proximity Module Layout - Mid1
Figure 56 Touch+Proximity Module Layout - Mid2
Figure 57 Touch+Proximity Module Layout - Bottom
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
70
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
8 REFERENCES
[1] Capacitive Touch Sensing Layout guidelines on www.semtech.com
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
71
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
9 PACKAGING INFORMATION
9.1 Packag e Ou tl in e Dra wing
SX8636 is ass embled in a MLPQ-UT28 package as shown in Figure 58.
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 APPLIES TO THE 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 C A B
D/2 bxN
Figure 58 Package O utline Drawing
9.2 Land Pattern
The land pattern of MLPQ-UT28 package, 4 mm x 4 mm is shown in Figure 59.
Figure 59 Land Pattern
WIRELESS & SENSING
Revision 8_1, December 15 © 2012 Semtech Corp. www.semtech.com
72
SX8636
Low Power, Capacitive Button Touch Controller (8 sensors)
with Enhanced LED Drivers and Proximity Sensing
CONTACT INFORMATION
© Semtech 2012
All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the
copyright o wner. The i nform ation presente d in this do cument does not form part of an y quotation or c ontract , 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 CUSTOMER’ S OWN RISK. Sho uld a c us t omer pur chas e or use Semtech
products f or an y such unauthor ized appl ication, th e cus tom er shall indem nif y and hold Sem tech and its officers,
employees, subsidiaries, affiliates, and distributors harmless against all claims, costs damages and attorney
fees which could arise.
Notice: All referenced brands, product names, service names and trademarks are the property of their
respective owners.
Semtech Corporation
Wireless and Sensing Products Division
200 Flynn Road, Camarillo, CA 93012
Phone: (805) 498-2111 Fax: (805) 498-3804
Mouser Electronics
Authorized Distributor
Click to View Pricing, Inventory, Delivery & Lifecycle Information:
Semtech:
SX8636I05AULTRT