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SX8644

Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

ENERAL

ESCRIPTION

The SX8644 is an ultra low power, fully integrated

12-channel solution for capacitive touch-buttons and

slider applications. Unlike many capacitive touch

solutions, the SX8644 features dedicated capacitive

sense inputs (that requires no external components)

in addition to 8 general purpose I/O ports (GPIO).

Each GPIO is typically configured as LED driver with

independent PWM source for enhanced lighting

control such as intensity and fading.

The SX8644 includes a capacitive 10 bit ADC analog

interface with automatic compensation up to 100pF.

The high resolution capacitive sensing supports a

wide variety of touch pad sizes and shapes and

allows capacitive buttons to be created using thick

overlay materials (up to 5mm) for an extremely

robust and ESD immune system design.

The SX8644 incorporates a versatile firmware that

was specially designed to simplify capacitive touch

solution design and offers reduced time-to-market.

Integrated multi-time programmable memory

provides the ultimate flexibility to modify key firmware

parameters (gain, threshold, scan period, auto offset

compensation… ) in the field without the need for

new firmware development.

The SX8644 supports the 400 kHz I²C serial bus

data protocol and includes a field programmable

slave address. The SX8644 is available in a tiny

MLPQ 5mm x 5mm package. The small footprint

make it an ideal solution for portable, battery

powered applications where power and density are

at a premium.

YPICAL

PPLICATION CIRCUIT

RODUCT

EATURES

 Complete Twelve Sensors Capacitive Touch Controller for

Buttons and Slider

 Pre-configured for 6 Buttons and a Slider

 8 LED Drivers with Individual Intensity, Fading Control

and Autolight Mode

 256 steps PWM Linear and Logarithmic control

 High Resolution Capacitive Sensing

 Up to 100pF of Offset Capacitance Compensation at

Full Sensitivity

 Capable of Sensing through Overlay Materials up to

5mm thick

 Extremely Low Power Optimized for Portable Application

 8uA (typ) in Sleep Mode

 80uA (typ) in Doze Mode (Scanning Period 195ms)

 220uA (typ) in Active Mode (Scanning Period 30ms)

 Programmable Scanning Period from 15ms to 1500ms

 Auto Offset Compensation

 Eliminates False Triggers due to Environmental

Factors (Temperature, Humidity)

 Initiated on Power-up and Configurable Intervals

 Multi-Time In-Field Programmable Firmware Parameters

for Ultimate Flexibility

 On-chip user programmable memory for fast, self

contained start-up

 "Smart" Wake-up Sequence for Easy Activation from Doze

 No External Components per Sensor Input

 Internal Clock Requires No External Components

 Differential Sensor Sampling for Reduced EMI

 400 KHz Fast-Mode I²C Interface with Interrupt

 -40°C to +85°C Operation

PPLICATIONS

 Notebook/Netbook/Portable/Handheld computers

 Cell phones, PDAs

 Consumer Products, Instrumentation, Automotive

 Mechanical Button Replacement

RDERING

NFORMATION

Part Number Temperature

Range Package

SX8644I05AWLTRT

-40°C to +85°C Lead Free MLPQ-W32

3000 Units/reel

* This device is RoHS/WEEE compliant and Halogen Free

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SX8644

Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

Table of Contents

ENERAL

ESCRIPTION

........................................................................................................................1

YPICAL

PPLICATION CIRCUIT

............................................................................................................1

RODUCT

EATURES

.....................................................................................................................1

PPLICATIONS

.......................................................................................................................................1

RDERING

NFORMATION

......................................................................................................................1

ENERAL

ESCRIPTION

...............................................................................................................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

LECTRICAL

HARACTERISTICS

.................................................................................................7

2.1

Absolute Maximum Ratings 7

2.2

Recommended Operating Conditions 7

2.3

Thermal Characteristics 7

2.4

Electrical Specifications 8

UNCTIONAL DESCRIPTION

........................................................................................................10

3.1

Quickstart Application 10

3.2

Introduction 10

3.2.1

General 10

3.2.2

GPIOs 11

3.2.3

Parameters 11

3.2.4

Configuration 11

3.3

Scan Period 12

3.4

Operation modes 12

3.5

Sensors on the PCB 14

3.6

Button and Slider Information 15

3.6.1

Button Information 15

3.6.2

Slider Information 15

3.7

Analog Sensing Interface 17

3.8

Offset Compensation 18

3.9

Processing 19

3.10

Configuration 19

3.11

Power Management 21

3.12

Clock Circuitry 21

3.13

I2C interface 21

3.14

Reset 22

3.14.1

Power up 22

3.14.2

RESETB 22

3.14.3

Software Reset 23

3.15

Interrupt 24

3.15.1

Power up 24

3.15.2

Assertion 24

3.15.3

Clearing 24

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SX8644

Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

3.15.4

Example 25

3.16

General Purpose Input and Outputs 25

3.16.1

Introduction and Definitions 25

3.16.2

GPI 26

3.16.3

GPP 26

3.16.4

GPO 27

3.16.5

Intensity index vs PWM pulse width 30

3.17

Smart Wake Up 31

IN DESCRIPTIONS

.....................................................................................................................32

4.1

Introduction 32

4.2

ASI pins 32

4.3

Host interface pins 33

4.4

Power management pins 36

4.5

General purpose IO pins 37

ETAILED

ONFIGURATION DESCRIPTIONS

..............................................................................38

5.1

Introduction 38

5.2

General Parameters 41

5.3

Capacitive Sensors Parameters 42

5.4

Button Parameters 47

5.5

Slider Parameters 51

5.6

Mapping Parameters 55

5.7

GPIO Parameters 58

I2C

NTERFACE

...........................................................................................................................62

6.1

I2C Write 62

6.2

I2C read 63

6.3

I2C Registers Overview 64

6.4

Status Registers 65

6.5

Control Registers 68

6.6

SPM Gateway Registers 70

6.6.1

SPM Write Sequence 71

6.6.2

SPM Read Sequence 72

6.7

NVM burn 73

PPLICATION

NFORMATION

......................................................................................................74

ACKAGING

NFORMATION

........................................................................................................75

8.1

Package Outline Drawing 75

8.2

Land Pattern 75

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SX8644

Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

1 G

ENERAL

ESCRIPTION

1.1 Pin Diagram

SX8644

Top View

9 10 11 12 13 14 15 16

2526272829303132

bottom ground pad

cap2

cap3

cap4

cap5

cap6

cap8

cap7

cap9

gnd

gpio5

gpio4

gpio3

gpio2

gpio1

gnd

gpio0

cap1

cap0

vana

resetb

gnd

gpio7

vdig

gpio6

cap10

cap11

vdd

scl

intb

sda

Figure 1

Pinout Diagram

1.2 Marking information

SX8644

yyww

xxxxxx

R05

yyww = Date Code

xxxxxx = Semtech lot number

R05 = Semtech Code

Figure 2

Marking Information

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SX8644

Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

1.3 Pin Description

Number Name Type Description

1 CAP2 Analog Capacitive Sensor 2

2 CAP3 Analog Capacitive Sensor 3

3 CAP4 Analog Capacitive Sensor 4

4 CAP5 Analog Capacitive Sensor 5

5 CAP6 Analog Capacitive Sensor 6

6 CAP7 Analog Capacitive Sensor 7

7 CAP8 Analog Capacitive Sensor 8

8 CAP9 Analog Capacitive Sensor 9

9 CAP10 Analog Capacitive Sensor 10

10 CAP11 Analog Capacitive Sensor 11

11 CN Analog Integration Capacitor, negative terminal (1nF between CN and CP)

12 CP Analog Integration Capacitor, positive terminal (1nF between CN and CP)

13 VDD Power Main input power supply

14 INTB Digital Output Interrupt, active LOW, requires pull up resistor (on host or external)

15 SCL Digital Input I2C Clock, requires pull up resistor (on host or external)

16 SDA Digital Input/Output I2C Data, requires pull up resistor (on host or external)

17 GPIO0 Digital Input/Output General Purpose Input/Output 0

18 GPIO1 Digital Input/Output General Purpose Input/Output 1

19 GND Ground Ground

20 GPIO2 Digital Input/Output General Purpose Input/Output 2

21 GPIO3 Digital Input/Output General Purpose Input/Output 3

22 GPIO4 Digital Input/Output General Purpose Input/Output 4

23 GPIO5 Digital Input/Output General Purpose Input/Output 5

24 GND Ground Ground

25 GPIO6 Digital Input/Output General Purpose Input/Output 6

26 GPIO7 Digital Input/Output General Purpose Input/Output 7

27 VDIG Analog Digital Core Decoupling, connect to a 100nF decoupling capacitor

28 GND Ground Ground

29 RESETB Digital Input Active Low Reset. Connect to VDD if not used.

30 VANA Analog Analog Core Decoupling, connect to a 100nF decoupling capacitor

31 CAP0 Analog Capacitive Sensor 0

32 CAP1 Analog Capacitive Sensor 1

bottom plate GND Ground Exposed pad connect to ground

Table 1

Pin description

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SX8644

Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

1.4 Simplified Block Diagram

The simplified block diagram of the SX8644 is illustrated in Figure 3.

SX8644

cap2

cap3

cap4

cap5

cap6

cap8

cap7

cap9

gnd

gpio5

gpio4

gpio3

gpio2

gpio1

gnd

gpio0

cap1

cap0

vana

resetb

gnd

gpio7

vdig

gpio6

cap10

cap11

vdd

scl

intb

sda

analog

sensor

interface

micro

processor

RAM

ROM I2C

GPIO

controller

power management

clock

generation

PWM

LED

controller

bottom plate

NVM

Figure 3

Simplified block diagram of the SX8644

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

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Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

2 E

LECTRICAL

HARACTERISTICS

2.1 Absolute Maximum Ratings

Stresses above the values listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress

rating only and functional operation of the device at these, or any other conditions beyond the “Recommended Operating

Conditions”, is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability

Parameter Symbol Min. Max. Unit

Supply Voltage VDD -0.5 3.9 V

Input voltage (non-supply pins) V

-0.5 3.9 V

Input current (non-supply pins) I

10 mA

Operating Junction Temperature T

JCT

125 °C

Reflow temperature T

260 °C

Storage temperature T

STOR

-50 150 °C

ESD HBM (Human Body model)

(i)

ESD

HBM

3 kV

Latchup

(ii)

± 100 mA

Table 2

Absolute Maximum Ratings

(i) Tested to JEDEC standard JESD22-A114

(ii) Tested to JEDEC standard JESD78

2.2 Recommended Operating Conditions

Parameter Symbol Min. Max. Unit

Supply Voltage VDD 2.7V 3.6 V

Supply Voltage Drop

(iii, iv, v)

VDD

drop

100 mV

Supply Voltage for NVM programming VDD 3.0V 3.6 V

Ambient Temperature Range T

-40 85 °C

Table 3

Recommended Operating 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 SX8644 may

require;

- a hardware reset issued by the host using the RESETB pin

- a software reset issued by the host using the I2C interface

(v) In the event the host processor is reset or undergoes a power OFF/ON cycle, it is recommended that the host also resets

the SX8644 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)

25 °C/W

Table 4

Thermal Characteristics

(

vi) Static airflow

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SX8644

Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

2.4 Electrical Specifications

All values are valid within the operating conditions unless otherwise specified.

Parameter Symbol Conditions Min. Typ. Max. Unit

Current consumption

Active mode, average I

OP,active

30ms scan period,

12 sensors enabled,

minimum sensitivity

220

300 uA

Doze mode, average I

OP,Doze

195ms scan period,

12 sensors enabled,

minimum sensitivity

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

0.7*VDD VDD + 0.3V V

Input logic low V

VSS applied to GND pins VSS - 0.3V 0.8 V

Input leakage current L

CMOS input ±1 uA

Pull up resistor R

when enabled 660 kΩ

Pull down resistor R

when enabled 660 kΩ

GPIO set as Output, INTB, SDA

Output logic high V

<4mA VDD-0.4 V

Output logic low V

OL,GPIO

<12mA

OL,SDA,INTB

<4mA 0.4 V

Start-up

Power up time t

por

time between rising edge

VDD and rising INTB 150 ms

RESETB

Pulse width t

res

50 ns

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, tolerance +/-10% 1 nF

Capacitor between VDD, GND C

vdd

type 0402, tolerance +/-50% 100 nF

Table 5

Electrical Specifications

Parameter Symbol Conditions Min. Typ. Max. Unit

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SX8644

Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

Parameter Symbol Conditions Min. Typ. Max. Unit

I2C Timing Specifications (i)

SCL clock frequency f

SCL

400 KHz

SCL low period t

LOW

1.3 us

SCL high period t

HIGH

0.6 us

Data setup time t

SU;DAT

100 ns

Data hold time t

HD;DAT

0 ns

Repeated start setup time t

SU;STA

0.6 us

Start condition hold time t

HD;STA

0.6 us

Stop condition setup time t

SU;STO

0.6 us

Bus free time between stop and start

BUF

500 us

Input glitch suppression t

50 ns

Table 6

I2C Timing Specification

Notes:

(i) All timing specifications, Figure 4 and Figure 5, refer to voltage levels (V

, V

) defined in Table 5.

The interface complies with slave F/S mode as described by NXP: “I2C-bus specification, Rev. 03 - 19 June 2007”

Figure 4

I2C Start and Stop timing

Figure 5

I2C Data timing

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Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

3 F

UNCTIONAL DESCRIPTION

3.1 Quickstart Application

The SX8644 is preconfigured (Quickstart Application) for an application with 6 buttons, a slider (consisting of 6

sensors) and 8 LED drivers using logarithmic PWM fading.

Implementing a schematic based on Figure 6 will be immediately operational after powering without programming

the SX8644 (even without host).

cap2

cap3

cap4

cap5

gnd

gpio5

gpio4

gpio3

gpio2

gpio1

gnd

gpio0

cap1

cap0

vana

resetb

gnd

gpio7

vdig

gpio6

vdd

scl

intb

sda

analog

sensor

interface

micro

processor

RAM

ROM

NVM

I2C

GPIO

controller

power management

clock

generation

PWM

LED

controller

bottom plate

SX8644

HOST

cap6

cap8

cap7

cap9

cap10

cap11

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 CAP5) have their own LED associated on a GPIO pin showing a touch or a release.

The sensors on CAP6 to CAP11 are used in a slider configuration. A moving finger on the slider will enable the

LED on GPIO6 or GPIO7 indicating the finger movement.

The sensor detection and the LED fading described above are operational without any host interaction.

This is made possible using the SX8644 Autolight feature described in the following sections.

3.2 Introduction

3.2.1 General

The SX8644 is intended to be used in applications which require capacitive sensors covered by isolating overlay

material. A finger approaching the capacitive sensors will change the charge that can be loaded on the sensors.

The SX8644 measures the change of charge and converts that into digital values (ticks). The larger the charge on

the sensors, the larger the number of ticks will be. The charge to ticks conversion is done by the SX8644 Analog

Sensor Interface (ASI).

The ticks are further processed by the SX8644 and converted in a high level, easy to use information for the

user’s host.

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Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

The information between SX8644 and the user’s host is passed through the I2C interface with an additional

interrupt signal indicating that the SX8644 has new information. For buttons this information is simply touched or

released.

3.2.2 GPIOs

A second path of feedback to the user is using General Purpose Input Output (GPIO) pins. The SX8644 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 SX8644 has eight individual PWM generators, one for each GPIO pin.

The LED fading can be initiated automatically by the SX8644 by setting the SX8644 Autolight feature. A simple

touch on a sensor and the corresponding LED will fade-in without any host interaction over the I2C.

In case the Autolight feature is disabled then the host will decide to start a LED fading-in period, simply by setting

the GP0 pin to ‘high’ using one I2C command. The SX8644 will then slowly fade-in the LED using the PWM

autonomously.

In case the host needs to have full control of the LED intensity then the host can set the GPIO in GPP mode. The

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 SX8644 has many low level built-in, fixed algorithms and procedures. To allow a lot of freedom for the user

and adapt the SX8644 for different applications these algorithms and procedures can be configured with a large

set of parameters which will be described in the following sections. Examples of parameters are which sensors

are buttons or which sensors are parts of a slider, 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

SX8644 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 SX8644. The programming needs to be done once (over the I2C). The SX8644 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 done by

additional I2C communications.

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Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

3.3 Scan Period

The basic operation Scan period of the SX8644 sensing interface can be split into three periods over time.

In the first period (Sensing) the SX8644 is sensing all enabled CAP inputs, from CAP0 towards CAP11.

In the second period (Processing) the SX8644 processes the sensor data, verifies and updates the GPIO and I2C

status registers.

In the third period (Timer) the SX8644 is set in a low power mode and waits until a new cycle starts.

Figure 7 shows the different SX8644 periods over time.

Figure 7

Scan Period

The scan period determines the minimum reaction time of the SX8644. The scan period can be configured by 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 SX8644

generates the interrupt on the INTB pin. The shorter the scan period the faster the reaction time will be.

Very low power consumption can be obtained by setting very long scan periods with the expense of having longer

reaction times.

Important: All external events like GPIO, I2C and INTB are updated in the processing period, so once every scan

period. If e.g. a GPI would change state directly after the processing period then this will be reported with a delay

of one scan period later in time.

3.4 Operation modes

The SX8644 has 3 operation modes. The main difference is found in the reaction time (corresponding to the scan

period) and power consumption.

Active mode offers fast scan periods. The typical reaction time is 30ms. All enabled sensors are scanned and

information data is processed within this interval.

Doze mode increases the scan period time which increases the reaction time to 195ms typical and at the same

time reduces the operating current.

Sleep mode turns the SX8644 OFF, except for the I2C and GPI peripheral, minimizing operating current while

maintaining the power supplies. In Sleep mode the SX8644 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 most applications the reaction time needs to be fast when fingers are present, but can be slow when no person

uses the application. In case the SX8644 is not used for a specific time it can go from Active mode into Doze

mode and power will be saved. This time-out is determined by the Passive Timer which can be configured by the

user or turned OFF if not required.

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Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

To leave Doze mode and enter Active mode this can be done by a simple touch on any button.

For some applications a single button touch might cause undesired wakening up and Active mode would be

entered too often.

The SX8644 offers therefore a smart wake-up sequence feature in which the user needs to touch and release a

correct sequence of buttons before Active mode will be entered. This is explained in more detail in the Wake-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 SX8644.

The diagram in Figure 8 shows the available operation modes and the possible transitions.

Figure 8

Operation modes

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Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

3.5 Sensors on the PCB

The capacitive sensors are relatively simple copper areas on the PCB connected to the twelve SX8644 capacitive

sensor input pins (CAP0…CAP11).The sensors are covered by isolating overlay material (typically 1mm...3mm).

The area of a sensor is typically one square centimeter which corresponds about to the area of a finger touching

the overlay material.

The capacitive sensors can be setup as ON/OFF buttons (see example Figure 9) or arranged in a slider

configuration (see example Figure 10) for e.g. menu scrolling or volume control applications.

Figure 9 PCB top

layer of four sensors for buttons

(surrounded by a ground plane)

Figure 10

PCB top layer of one slider using six sensors

(surrounded by ground plane)

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Touch Controller (12 sensors) with Enhanced LED Drivers

3.6 Button and Slider Information

3.6.1 Button Information

The buttons have two simple states (see Figure 11): ON (touched by finger) and OFF (released and no finger

press).

Figure 11

Buttons

A finger is detected as soon as the number of ticks from the ASI reaches a user-defined threshold plus a

hysteresis.

A release is detected if the ticks from the ASI go below the threshold minus a hysteresis. The hysteresis around

the threshold avoids rapid touch and release signaling during transients.

3.6.2 Slider Information

In case sensors are arranged in a slider configuration the ON, OFF information remains available as if it would be

a single sensor button.

Figure 12

Slider ON, OFF

Wherever the slider is touched the information will be set to ON. If no finger is present the slider information will be

OFF.

Due to the 2 dimensional character of the slider more information can be derived by processing the ticks.

During a touch a finger will influence most of the time the charge on one or two sensors but never all of the

sensors at the same time. Some sensor ticks will be larger than others based on the finger position.

The processing algorithms can therefore determine where the finger is positioned on the slider.

Interpolation between sensors increases the resolution beyond the number of sensors in the slider.

The interpolation can be done already on the PCB sensor structures (analog, like the chevron slider in Figure 10)

and as well by SX8644 digital processing of the ticks using center of gravity calculations.

The position of the finger on the PCB structures varies between the minimum zero and a user defined maximum

(Figure 13).

....x...

position

min max

Figure 13

Slider Position

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Ultra Low Power, Capacitive Button and Slider

Touch Controller (12 sensors) with Enhanced LED Drivers

The position belonging to the minimum and associated to a sensor is defined arbitrarily. The SX8644 defines the

minimum position to the sensor with the lowest CAP pin index. E.g. if CAP0 is a button (or disabled) and CAP1 to

CAP7 are the sensors of the slider then the position ‘zero’ starts at CAP1 and the maximum is found at CAP7.

In addition to the slider position, the SX8644 allows to detect finger movements. The movement occurs if the

finger position changes a certain step size between two succeeding scan periods. A very slow moving finger will

not be considered as a movement as the changing position will be minor. The SX8644 allows detecting a move

low (direction max to min) (see Figure 14) and a move high (direction min to max) (see Figure 15).

min max

Figure 14

Slider Move Low

Figure 15

Slider Move High

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3.7 Analog Sensing Interface

The Analog Sensing Interface (ASI) converts the charge on the sensors into ticks which will be further digitally

processed. The basic principle of the ASI will be explained in this section.

The ASI consists of a multiplexer selecting the sensor, analog switches, a reference voltage, an ADC sigma delta

converter, an offset compensation DAC and an external integration capacitor (see Figure 16).

switches

cap2

cap9

cap10

cap11

cap1

cap0 analog

multi-

plexor

Offset

compensation

DAC

ADC

ticks (raw)

compensation DCV

ASI processing

Cint

voltage

reference

low pass

ticks-diff

ticks-ave

Figure 16

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 cap (e.g. CAP0) will be accumulated multiple times on the external integration capacitor,

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

difference of charge will be converted to zero ticks if no finger is present and the number 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 SX8644 allows setting the sensitivity for each sensor individually in applications which have a variety of

sensors sizes or different overlays or for fine-tuning performances. The optimal sensitivity is depending heavily on

the final application. If the sensitivity is too low the ticks will not pass the thresholds and it is not possible to detect

fingers. In case the sensitivity is set too large a finger hovering above the sensors will already be detected before

the finger really touches the overlay resulting in false detections.

Once the ASI has finished the first sensor, the ticks are stored and the ASI will start measuring the next sensor

until all (enabled) sensors pins have been treated.

In case some sensors are disabled then these result in lower power consumption simply because the ASI is active

for a shorter period and the following processing period will be shorter.

The ticks from the ASI will then be handled by the digital processing.

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3.8 Offset Compensation

The capacitance at the CAP pins is determined by an intrinsic capacitance of the integrated circuit, the PCB

traces, ground coupling and the sensor planes. This capacitance is relatively large and might become easily 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 capacitance. This would require a very precise, high resolution ADC and complicated, power consuming,

digital processing.

The SX8644 features a 16 bit DAC which compensates for the large, slow varying capacitance already in front 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 SX8644 the Digital Compensation Values (DCV) are estimated 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 SX8644 is shut down the compensation values will be lost. At a next power-up the procedure starts all over

again. This assures that the SX8644 will operate under any condition. Powering up at e.g. different temperatures

will not change the performance of the SX8644 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 SX8644 will initiate a compensation procedure

and find a new set of DCVs.

Compensation procedures can as well be initiated by the SX8644 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.

Finally the host can initiate a compensation procedure by using the I2C interface (in Active or Doze mode). This is

e.g. required after the host changed the sensitivity of sensors.

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3.9 Processing

The first processing step of the raw ticks, coming out of the ASI, is low pass filtering to obtain an estimation of the

average capacitance: tick-ave (see Figure 17).

This slowly varying average is important in the detection of slowly changing environmental changes.

ticks (raw)

compensation DCV

ASI processing

low pass

tick-diff

tick-ave

processing

GPIO

controller

PWM LED

controller

I2C

SPM

Figure 17

Processing

The difference of the tick average and the raw ticks, tick-diff, is a good estimation of rapid changing input

capacitances.

The tick-diff, tick-ave and the configuration parameters in the SPM are then processed and determines the sensor

information, I2C registers status and PWM control.

3.10 Configuration

Figure 18 shows the building blocks used for configuring the SX8644.

Figure 18

Configuration

The default configuration parameters of the SX8644 are stored in the Quick Start Memory (QSM). This

configuration data is setup to a very common application for the SX8644 with 6 buttons and a slider. Without any

programming or host interaction the SX8644 will startup in the Quick Start Application.

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The QSM settings are fixed and can not be changed by the user.

In case the application needs different settings than the QSM settings then the SX8644 can be setup and/or

programmed over the I2C interface.

The configuration parameters of the SX8644 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 SX8644 checks if the NVM contains valid data. In that case the configuration parameter source

becomes the NVM. If the NVM is empty or non-valid then the configuration source becomes the QSM. In the next

step the SX8644 copies the configuration parameter source (QSM or NVM) into the Shadow Parameter Memory

(SPM). The SX8644 is operational and uses the configuration parameters of the SPM.

During power down or reset event the SPM loses all content. It will automatically be reloaded (from QSM or NVM)

following power up or at the end of the reset event.

The host will interface with the SX8644 through the I2C bus.

The I2C of the SX8644 consists of 16 registers. Some of these I2C registers are used to read the status and

information of the button and the slider. Other I2C registers allow the host to take control of the SX8644. The host

can e.g. decide to change the operation mode from Active mode to Doze mode or go into Sleep (according to

Figure 8).

Two additional modes allow the host to have an access to the SPM or indirect access to the NVM.

These modes are required during development, can be used in real time or in-field programming.

Figure 19 shows the Host SPM mode. In this mode the host can decide to overwrite the SPM. This is useful

during the development phases of the application where the configuration parameters are not yet fully defined and

as well during the operation of the application if some parameters need to be changed dynamically.

Figure 19

Host SPM mode

The content of the SPM remains valid as long as the SX8644 is powered and no reset is performed. After a power

down or reset the host needs to re-write the SPM if relevant for the application.

Figure 20 shows the Host NVM mode. In this mode the host will be able to write the NVM.

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Figure 20

Host NVM mode

The writing of the host towards the NVM is not done directly but done in 2 steps (Figure 20).

In the first step the host writes to the SPM (as in Figure 19). In the second step the host signals the SX8644 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 parameter set is determined this can be written to the NVM over the I2C using the 2 steps approach 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 SX8644 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 between VDIG and ground (see

Table 5). Both regulators are designed to only drive the SX8644 internal circuitry and must not be loaded

externally.

3.12 Clock Circuitry

The SX8644 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 SX8644.

The I2C slave implemented on the SX8644 is compliant with the standard (100kb/s) and fast mode (400kb/s)

The default SX8644 I2C address equals 0b010 1011.

A different I2C address can be programmed by the user in the NVM.

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3.14 Reset

The reset can be performed by 3 sources:

- power up,

- RESETB pin,

- software reset.

3.14.1 Power up

During power up the INTB is kept low. Once the power up sequence is terminated the INTB is released

autonomously. The SX8644 is then ready for operation.

Figure 21

Power Up vs. INTB

During the power on period the SX8644 stabilizes the internal regulators, RC clocks and the firmware initializes all

registers.

During the power up the SX8644 is not accessible and I2C communications are forbidden.

As soon as the INTB rises the SX8644 will be ready for I2C communication.

3.14.2 RESETB

When RESETB is driven low the SX8644 will reset and start the power up sequence as soon as RESETB is

driven high or pulled high.

In case the user does not require a hardware reset control pin then the RESETB pin can be connected to VDD.

Figure 22

Hardware Reset

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3.14.3 Software Reset

To perform a software reset the host needs to write 0xDE followed by 0x00 at the SoftReset register at address

0xB1.

Figure 23

Software Reset

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3.15 Interrupt

3.15.1 Power up

During power up the INTB is kept low. Once the power up sequence is terminated the INTB is released

autonomously. The SX8644 is then ready for operation.

Figure 24

Power Up vs. INTB

During the power on period the SX8644 stabilizes the internal regulators, RC clocks and the firmware initializes all

registers.

During the power up the SX8644 is not accessible and I2C communications are forbidden.

As soon as the INTB rises the SX8644 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 release if enabled). I2C registers CapStatMsb and CapStatLsb show the

detailed status of the Buttons,

• if a Slider event occurred (touch, release, move high, move low or position change). I2C registers

CapStatMsb, SldPosMsb and SldPosLsb show the detailed status of the Slider,

• if a GPI edge occurred (rising or falling if enabled). I2C register GpiStat shows the detailed status of the GPI

pins,

• when actually entering Active or Doze mode either through automatic wakeup or via host request (may be

delayed by 1 scan period). I2C register CompOpmode shows the current operation mode,

• once compensation procedure is completed either through automatic trigger or via host request (may be

delayed by 1 scan period),

• once SPM write is effective (may be delayed by 1 scan period),

• once NVM burn procedure is completed (may be delayed by 1 scan period),

• during reset (power up, hardware RESETB, software reset).

3.15.3 Clearing

INTB is updated in Active or Doze mode once every scan period.

The clearing of the INTB is done as soon as the host performs a read to the IrqSrc I2C register or reset is

completed

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3.15.4 Example

A typical example of the assertion and clearing of the INTB and the I2C communication is shown in Figure 25.

Figure 25

Interrupt and I2C

When a button is touched the SX8644 will assert the interrupt (1). The host will read the IrqSrc information over

the I2C and this clears the interrupt (2).

If the finger releases the button the interrupt will be asserted (3). The host reading the IrqSrc information will clear

the interrupt (4).

In case the host does not react to an interrupt this results in a missing touch.

3.16 General Purpose Input and Outputs

3.16.1 Introduction and Definitions

The SX8644 offers eight General Purpose Input and Outputs (GPIO) pins which can be configured in any of these

modes:

- GPI (General Purpose Input)

- GPP (General Purpose PWM)

- GPO (General Purpose Output)

Each of these modes is described in more details in the following sections.

The polarity of the GPP and GPO pins is defined as in figure below, driving an LED as example. It has to be set

accordingly in SPM parameter GpioPolarity.

Figure 26

Polarity definition, (a) normal, (b) inverted

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The PWM blocks used in GPP and GPO modes are 8-bits based and clocked at 2MHz typ. hence offering 256

selectable pulse width values with a granularity of 128us typ.

Figure 27 PWM definition, (a) small pulse width, (b) large pulse width

3.16.2 GPI

GPIOs configured as GPI will operate as digital inputs with standard low and high logic levels.

Optional pull-up/down and debounce can be enabled. Each GPI is individually edge programmable for INTB

generation which will also exit Sleep/Doze mode if relevant.

SPM/I2C parameters applicable in GPI mode are listed in table below. Please refer to the relevant SPM/I2C

parameters sections for more details.

GPI

GpioMode X

GpioPullUpDown X

GpioInterrupt X

SPM

GpioDebounce X

IrqSrc[4] X

I2C GpiStat X

Table 7

SPM/I2C Parameters Applicable in GPI Mode

3.16.3 GPP

GPIOs configured as GPP will operate as PWM outputs directly controlled by the host. A typical application is

LED dimming.

Typical GPP operation is illustrated in figure below.

Figure 28

LED 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.

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GPP

GpioMode X

GpioOutPwrUp X

GpioPolarity X

GpioIntensityOn X

GpioIntensityOff X

SPM

GpioFunction X

GppPinId X

I2C GppIntensity X

At power up, GppIntensity of each GPP pin is initialized with GpioIntensityOn or GpioIntensityOff depending on GpioOutPwrUp

corresponding bits value.

Table 8

SPM/I2C Parameters Applicable in GPP Mode

3.16.4 GPO

GPIOs configured as GPO will operate as digital outputs which can generate both standard low/high logic levels

and PWM low/high duty cycles levels. 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.

Figure 29 LED Control in GPO mode,

Autolight OFF

Figure 30 LED Control in GPO mode,

Autolight ON (mapped to Button)

Additionally these transitions can be configured to be done with or without fading following a logarithmic or linear

function. This is illustrated in figures below.

Figure 31

GPO ON transition (LED fade in), normal polarity, (a) linear, (b) logarithmic

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Figure 32

GPO ON transition (LED fade in), inverted polarity, (a) linear, (b) logarithmic

The fading out (e.g. after a button is released) is identical to the fading in but an additional off delay can be added

before the fading starts (Figure 33 and Figure 34).

Figure 33

GPO OFF transition (LED fade out), normal polarity, (a) linear, (b) logarithmic

Figure 34

GPO OFF transition (LED fade out), inverted polarity, (a) linear, (b) logarithmic

Please note that standard high/low logic signals are just a specific case of GPO mode and can also be generated

simply by setting inc/dec time to 0 (ie OFF) and programming intensity OFF/ON to 0x00 and 0xFF.

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SPM/I2C parameters applicable in GPO mode are listed in table below.

GPO

GpioMode X

GpioOutPwrUp X

GpioAutoligth X

GpioPolarity X

GpioIntensityOn X

GpioIntensityOff X

GpioFunction X

GpioIncFactor X

GpioDecFactor X

GpioIncTime X

GpioDecTime X

SPM

GpioOffDelay X

I2C GpoCtrl X

Only if Autolight is OFF, else must be left to 0 (default value)

Only if Autolight is OFF, else ignored

Table 9

SPM/I2C Parameters Applicable in GPO Mode

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3.16.5 Intensity index vs PWM pulse width

Tables below are used to convert all intensity indexes parameters GpioIntensityOff, GpioIntensityOn and

GppIntensity but also to generate fading in GPO mode

During fading in(out), the index is automatically incremented(decremented) at every Inc(Dec)Time x

Inc(Dec)Factor until it reaches the programmed GpioIntensityOn(Off) value.

Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log Index Lin/Log

0 0/0 32 33/5 64 65/12 96 97/26 128 129/48 160 161/81 192 193/125 224 225/184

1 2/0 33 34/5 65 66/13 97 98/27 129 130/49 161 162/82 193 194/127 225 226/186

2 3/0 34 35/5 66 67/13 98 99/27 130 131/50 162 163/83 194 195/129 226 227/188

3 4/0 35 36/5 67 68/13 99 100/28 131 132/51 163 164/84 195 196/130 227 228/190

4 5/0 36 37/5 68 69/14 100 101/29 132 133/52 164 165/86 196 197/132 228 229/192

5 6/2 37 38/6 69 70/14 101 102/29 133 134/53 165 166/87 197 198/133 229 230/194

6 7/2 38 39/6 70 71/14 102 103/30 134 135/54 166 167/88 198 199/135 230 231/197

7 8/2 39 40/6 71 72/15 103 104/30 135 136/55 167 168/89 199 200/137 231 232/199

8 9/2 40 41/6 72 73/15 104 105/31 136 137/55 168 169/91 200 201/139 232 233/201

9 10/2 41 42/6 73 74/15 105 106/32 137 138/56 169 170/92 201 202/140 233 234/203

10 11/2 42 43/7 74 75/16 106 107/32 138 139/57 170 171/93 202 203/142 234 235/205

11 12/2 43 44/7 75 76/16 107 108/33 139 140/58 171 172/95 203 204/144 235 236/208

12 13/2 44 45/7 76 77/16 108 109/33 140 141/59 172 173/96 204 205/146 236 237/210

13 14/2 45 46/7 77 78/17 109 110/34 141 142/60 173 174/97 205 206/147 237 238/212

14 15/3 46 47/7 78 79/17 110 111/35 142 143/61 174 175/99 206 207/149 238 239/215

15 16/3 47 48/8 79 80/18 111 112/35 143 144/62 175 176/100 207 208/151 239 240/217

16 17/3 48 49/8 80 81/18 112 113/36 144 145/63 176 177/101 208 209/153 240 241/219

17 18/3 49 50/8 81 82/19 113 114/37 145 146/64 177 178/103 209 210/155 241 242/221

18 19/3 50 51/8 82 83/19 114 115/38 146 147/65 178 179/104 210 211/156 242 243/224

19 20/3 51 52/9 83 84/20 115 116/38 147 148/66 179 180/106 211 212/158 243 244/226

20 21/3 52 53/9 84 85/20 116 117/39 148 149/67 180 181/107 212 213/160 244 245/229

21 22/3 53 54/9 85 86/21 117 118/40 149 150/68 181 182/109 213 214/162 245 246/231

22 23/3 54 55/9 86 87/21 118 119/40 150 151/69 182 183/110 214 215/164 246 247/233

23 24/4 55 56/10 87 88/22 119 120/41 151 152/71 183 184/111 215 216/166 247 248/236

24 25/4 56 57/10 88 89/22 120 121/42 152 153/72 184 185/113 216 217/168 248 249/238

25 26/4 57 58/10 89 90/23 121 122/43 153 154/73 185 186/114 217 218/170 249 250/241

26 27/4 58 59/10 90 91/23 122 123/44 154 155/74 186 187/116 218 219/172 250 251/243

27 28/4 59 60/11 91 92/24 123 124/44 155 156/75 187 188/117 219 220/174 251 252/246

28 29/4 60 61/11 92 93/24 124 125/45 156 157/76 188 189/119 220 221/176 252 253/248

29 30/4 61 62/11 93 94/25 125 126/46 157 158/77 189 190/121 221 222/178 253 254/251

30 31/4 62 63/12 94 95/25 126 127/47 158 159/78 190 191/122 222 223/180 254 255/253

31 32/5 63 64/12 95 96/26 127 128/48 159 160/80 191 192/124 223 224/182 255 256/256

Table 10 Intensity index vs. PWM pulse 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

Intensity index vs. PWM pulse width (inverted polarity)

Recommended/default settings are inverted polarity (to take advantage from high sink current capability) and

logarithmic mode (due to the non-linear response of the human eye).

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3.17 Smart Wake Up

The SX8644 offers a smart wake up mechanism which allows waking-up from the Doze low power mode to the

Active mode in a secure/controlled way and not by any unintentional sensor activation.

Until the full correct wake-up sequence is entered, the SX8644 will remain in Doze mode. Any wrong key implies

the whole sequence to be entered again.

A sequence of up to 6 keys can be defined. Each key must be followed by a release to be validated.

The smart wake-up mechanism can also be disabled which implies that Doze mode can hence only be exited

from GPI or I2C command.

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4 P

IN DESCRIPTIONS

4.1 Introduction

This chapter describes briefly the pins of the SX8644, 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, ..., CAP11

The capacitance sensor pins (CAP0, CAP1, ..., CAP11) are connected directly to the ASI circuitry which converts

the sensed capacitance into digital values.

The capacitance sensor pins which are not used should be left open.

The enabled CAP pins need be connected directly to the sensors without significant resistance (typical below

some ohms, connection vias are allowed).

The capacitance sensor pins are protected to VANA and GROUND.

Figure 35 shows the simplified diagram of the CAP0, CAP1, ..., CAP11 pins.

SX8644

sensor ASI CAPx CAP_INx

VANA

Note : x = 0, 1,2,…11

Figure 35

Simplified diagram of CAP0, CAP1, ..., CAP11

CN, CP

The CN and the CP pins are connected to the ASI circuitry. A 1nF sampling capacitor between CP and CN needs

to be placed as close as possible to the SX8644.

The CN and CP are protected to VANA and GROUND.

Figure 36 shows the simplified diagram of the CN and CP pins.

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SX8644

ASI

VANA

Figure 36

Simplified diagram of CN and CP

4.3 Host interface pins

The host interface consists of the interrupt pin INTB, a reset pin RESETB and the standard I2C pins: SCL and

SDA.

INTB

The INTB pin is an open drain output that requires an external pull-up resistor (1..10 kOhm). The INTB pin is

protected to VDD using dedicated devices. The INTB pin has diode protected to GROUND.

Figure 37 shows a simplified diagram of the INTB pin.

VDD

R_INT

INTB

SX8644

INT

to host

Figure 37

Simplified diagram of INTB

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SCL

The SCL pin is a high impedance input pin. The SCL pin is protected to VDD, using dedicated devices, in order to

conform to standard I2C slave specifications. The SCL pin has diode protected to GROUND.

An external pull-up resistor (1..10 kOhm) is required on this pin.

Figure 38 shows the simplified diagram of the SCL pin.

VDD

R_SCL

SCL

SX8644

from host

SCL_IN

Figure 38

Simplified diagram of SCL

SDA

SDA is an IO pin that can be used as an open drain output pin with external pull-up resistor or as a high

impedance input pin. The SDA IO pin is protected to VDD, using dedicated devices, in order to conform to

standard I2C slave specifications. The SDA pin has diode protected to GROUND.

An external pull-up resistor (1..10 kOhm) is required on this pin.

Figure 39 shows the simplified diagram of the SDA pin.

VDD

R_SDA

SDA

SX8644

SDA_OUT

from/to host

SDA_IN

Figure 39

Simplified diagram of SDA

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RESETB

The RESETB pin is a high impedance input pin. The RESETB pin is protected to VDD using dedicated devices.

The RESETB pin has diode protected to GROUND.

Figure 40 shows the simplified diagram of the RESETB pin controlled by the host.

VDD

R_RESETB

RESETB

SX8644

from host

RESETB_IN

Figure 40

Simplified diagram of RESETB controlled by host

Figure 41 shows the RESETB without host control.

VDD

RESETB

SX8644

RESETB_IN

Figure 41

Simplified diagram of RESETB without host control

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4.4 Power management pins

The power management pins consist of the Power, Ground and Regulator pins.

VDD

VDD is a power pin and is the main power supply for the SX8644.

VDD has protection to GROUND.

Figure 42 shows a simplified diagram of the VDD pin.

VDD

SX8644

VDD

Figure 42

Simplified diagram of VDD

GND

The SX8644 has four ground pins all named GND. These pins and the package center pad need to be connected

to ground potential.

The GND has protection to VDD.

Figure 43 shows a simplified diagram of the GND pin.

VDD

SX8644

GND GND

Figure 43

Simplified diagram of GND

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VANA, VDIG

The SX8644 has on-chip regulators for internal use (pins VANA and VDIG).

VANA and VDIG have protection to VDD and to GND.

The output of the regulators needs to be de-coupled with a small 100nF capacitor to ground.

Figure 44 shows a simplified diagram of the VANA and VDIG pin.

VDD

SX8644

GND

VDIG

VDD

GND

VANA

VDIG

Cvdig

Cvana

Figure 44

Simplified diagram of VANA and VDIG

4.5 General purpose IO pins

The SX8644 has 8 General purpose input/output (GPIO) pins.

All the GPIO pins have protection to VDD and GND.

The GPIO pins can be configured as GPI, GPO or GPP.

Figure 45 shows a simplified diagram of the GPIO pins.

Figure 45

Simplified diagram of GPIO pins

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5 D

ETAILED

ONFIGURATION DESCRIPTIONS

5.1 Introduction

The SX8644 configuration parameters are taken from the QSM or the NVM and loaded into the SPM as explained

in the chapter ‘functional description’.

This chapter describes the details of the configuration parameters of the SX8644.

The SPM is split by functionality into 6 configuration sections:

• General section: operating modes,

• Capacitive Sensors section: related to lower level capacitive sensing,

• Button: related to the conversion from sensor data towards button information,

• Slider: related to the conversion from sensor data towards slider information,

• Mapping: related to mapping of button and slider information towards wake-up and GPIO pins,

• GPIO: related to the setup of the GPIO pins.

The total address space of the SPM and the NVM is 128 bytes, from address 0x00 to address 0x7F.

Two types of memory addresses, data are accessible to the user.

• ‘application data’: Application dependent data that need to be configured by the user.

• ‘reserved’: Data that need to be maintained by the user to the QSM default values (i.e. when NVM is burned).

The Table 12 and Table 13 resume the complete SPM address space and show the ‘application data’ and

‘reserved’ addresses, the functional split and the default values (loaded from the QSM).

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Address Name default QSM

value Address Name default QSM

value

0x00 Reserved 0xxx 0x20 Reserved 0x00

0x01 Reserved 0xxx 0x21 BtnCfg 0x30

0x02 Reserved 0x10 0x22 BtnAvgThresh 0x50

0x03 Reserved 0xxx 0x23 BtnCompNegThresh 0x50

0x04 I2CAddress 0x2B 0x24 BtnCompNegCntMax 0x01

0x05 ActiveScanPeriod 0x02 0x25 BtnHysteresis 0x0A

0x06 DozeScanPeriod 0x0D 0x26

Button

BtnStuckAtTimeout 0x00

0x07

General

PassiveTimer 0x00 0x27 SldCfg 0x00

0x08 Reserved 0x00 0x28 SldStuckAtTimeout 0x00

0x09 CapModeMisc 0x01 0x29 SldHysteresis 0x03

0x0A CapMode11_8 0xAA 0x2A Reserved 0xFF

0x0B CapMode7_4 0xA5 0x2B SldNormMsb 0x01

0x0C CapMode3_0 0x55 0x2C SldNormLsb 0x80

0x0D CapSensitivity0_1 0x00 0x2D SldAvgThresh 0x50

0x0E CapSensitivity2_3 0x00 0x2E SldCompNegThresh 0x50

0x0F CapSensitivity4_5 0x00 0x2F SldCompNegCntMax 0x01

0x10 CapSensitivity6_7 0x00 0x30 SldMoveThresh 0x02

0x11 CapSensitivity8_9 0x00 0x31 Reserved 0x00

0x12 CapSensitivity10_11 0x00 0x32

Slider

Reserved 0x00

0x13 CapThresh0 0xA0 0x33 MapWakeupSize 0x00

0x14 CapThresh1 0xA0 0x34 MapWakeupValue0 0x00

0x15 CapThresh2 0xA0 0x35 MapWakeupValue1 0x00

0x16 CapThresh3 0xA0 0x36 MapWakeupValue2 0x00

0x17 CapThresh4 0xA0 0x37 MapAutoLight0 0xFE

0x18 CapThresh5 0xA0 0x38 MapAutoLight1 0x54

0x19 CapThresh6 0xA0 0x39 MapAutoLight2 0x32

0x1A CapThresh7 0xA0 0x3A MapAutoLight3 0x10

0x1B CapThresh8 0xA0 0x3B MapAutoLightGrp0Msb 0x00

0x1C CapThresh9 0xA0 0x3C MapAutoLightGrp0Lsb 0x00

0x1D CapThresh10 0xA0 0x3D MapAutoLightGrp1Msb 0x00

0x1E CapThresh11 0xA0 0x3E MapAutoLightGrp1Lsb 0x00

0x1F

Capacitive Sensors

CapPerComp 0x00 0x3F

Mapping

MapSegmentHysteresis 0x02

Table 12

SPM address map: 0x00…0x3F

Note

• ‘0xxx’: write protected data

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Address Name default QSM

value Address Name default QSM

value

0x40 GpioMode7_4 0x00 0x60 GpioDecTime1_0 0x44

0x41 GpioMode3_0 0x00 0x61 GpioOffDelay7_6 0x00

0x42 GpioOutPwrUp 0x00 0x62 GpioOffDelay5_4 0x00

0x43 GpioAutoLight 0xFF 0x63 GpioOffDelay3_2 0x00

0x44 GpioPolarity 0x00 0x64 GpioOffDelay1_0 0x00

0x45 GpioIntensityOn0 0xFF 0x65 GpioPullUpDown7_4 0x00

0x46 GpioIntensityOn1 0xFF 0x66 GpioPullUpDown3_0 0x00

0x47 GpioIntensityOn2 0xFF 0x67 GpioInterrupt7_4 0x00

0x48 GpioIntensityOn3 0xFF 0x68 GpioInterrupt3_0 0x00

0x49 GpioIntensityOn4 0xFF 0x69

Gpio

GpioDebounce 0x00

0x4A GpioIntensityOn5 0xFF 0x6A Reserved 0x00

0x4B GpioIntensityOn6 0xFF 0x6B Reserved 0x00

0x4C GpioIntensityOn7 0xFF 0x6C Reserved 0x00

0x4D GpioIntensityOff0 0x00 0x6D Reserved 0x00

0x4E GpioIntensityOff1 0x00 0x6E Reserved 0x00

0x4F GpioIntensityOff2 0x00 0x6F Reserved 0x50

0x50 GpioIntensityOff3 0x00 0x70 Reserved 0x46

0x51 GpioIntensityOff4 0x00 0x71 Reserved 0x10

0x52 GpioIntensityOff5 0x00 0x72 Reserved 0x45

0x53 GpioIntensityOff6 0x00 0x73 Reserved 0x02

0x54 GpioIntensityOff7 0x00 0x74 Reserved 0xFF

0x55 Reserved 0xFF 0x75 Reserved 0xFF

0x56 GpioFunction 0x00 0x76 Reserved 0xFF

0x57 GpioIncFactor 0x00 0x77 Reserved 0xD5

0x58 GpioDecFactor 0x00 0x78 Reserved 0x55

0x59 GpioIncTime7_6 0x00 0x79 Reserved 0x55

0x5A GpioIncTime5_4 0x00 0x7A Reserved 0x7F

0x5B GpioIncTime3_2 0x00 0x7B Reserved 0x23

0x5C GpioIncTime1_0 0x00 0x7C Reserved 0x22

0x5D GpioDecTime7_6 0x44 0x7D Reserved 0x41

0x5E GpioDecTime5_4 0x44 0x7E Reserved 0xFF

0x5F

Gpio

GpioDecTime3_2 0x44 0x7F SpmCrc* 0x6F

Table 13

SPM address map: 0x40…0x7F

Note*

• SpmCrc: CRC depending on SPM content, updated in Active or Doze mode.

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5.2 General Parameters

General Parameters

Address Name Bits Description

7 Reserved 0x04 I2CAddress

6:0 Defines the I2C address (default 0x2B).

The I2C address will be active after a reset.

0x05 ActiveScanPeriod

7:0 Active Mode Scan Period ()

0x00: Reserved

0x01: 15ms

0x02: 30ms (default)

…

0xFF: 255 x 15ms

0x06 DozeScanPeriod 7:0 Doze Mode Scan Period ()

0x00: Reserved

0x01: 15ms

…

0x0D: 195ms (default)

…

0xFF: 255 x 15ms

0x07 PassiveTimer 7:0 Passive Timer on Button and Slider Information (Figure 8)

0x00: OFF (default)

0x01: 1 second

…

0xFF: 255 seconds

Table 14

General Parameters

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5.3 Capacitive Sensors Parameters

Capacitive Sensors Parameters

Address Name Bits Description

7:3 Reserved

2 IndividualSensitivity Defines common sensitivity for all sensors or individual

sensor sensitivity.

0: Common settings (CapSensitivity0_1[7:4])

1: Individual CAP sensitivity settings (CapSensitivityx_x)

0x09 CapModeMisc

1:0 Reserved Reserved: ‘01’

7:6 CAP11 Mode Slider

5:4 CAP10 Mode Slider

3:2 CAP9 Mode Slider

0x0A CapMode11_8

1:0 CAP8 Mode Slider

7:6 CAP7 Mode Slider

5:4 CAP6 Mode Slider

3:2 CAP5 Mode Button

0x0B CapMode7_4

1:0 CAP4 Mode Button

7:6 CAP3 Mode Button

5:4 CAP2 Mode Button

3:2 CAP1 Mode Button

0x0C CapMode3_0

1:0 CAP0 Mode

Defines the mode of

the CAP pin.

00: Disabled

01: Button

10: Slider

11: Reserved

Default

Button

7:4 CAP0 Sensitivity - Common Sensitivity 0x0D CapSensitivity0_1

3:0 CAP1 Sensitivity

7:4 CAP2 Sensitivity 0x0E CapSensitivity2_3

3:0 CAP3 Sensitivity

7:4 CAP4 Sensitivity 0x0F CapSensitivity4_5

3:0 CAP5 Sensitivity

7:4 CAP6 Sensitivity 0x10 CapSensitivity6_7

3:0 CAP7 Sensitivity

7:4 CAP8 Sensitivity 0x11 CapSensitivity8_9

3:0 CAP9 Sensitivity

7:4 CAP10 Sensitivity 0x12 CapSensitivity10_11

3:0 CAP11 Sensitivity

Defines the sensitivity.

0x0: Minimum (default)

0x7: Maximum

0x8…0xF: Reserved

0x13 CapThresh0 7:0 CAP0 Touch Threshold

0x14 CapThresh1 7:0 CAP1 Touch Threshold

0x15 CapThresh2 7:0 CAP2 Touch Threshold

0x16 CapThresh3 7:0 CAP3 Touch Threshold

0x17 CapThresh4 7:0 CAP4 Touch Threshold

0x18 CapThresh5 7:0 CAP5 Touch Threshold

0x19 CapThresh6 7:0 CAP6 Touch Threshold

Defines the Touch Threshold ticks.

0x00: 0,

0x01: 4,

…

0xA0: 640 (default),

…

0xFF: 1020

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Capacitive Sensors Parameters

Address Name Bits Description

0x1A CapThresh7 7:0 CAP7 Touch Threshold

0x1B CapThresh8 7:0 CAP8 Touch Threshold

0x1C CapThresh9 7:0 CAP9 Touch Threshold

0x1D CapThresh10 7:0 CAP10 Touch Threshold

0x1E CapThresh11 7:0 CAP11 Touch Threshold

7:4 Reserved 0x1F CapPerComp

3:0 Periodic Offset Compensation Defines the periodic offset compensation.

0x0: OFF (default)

0x1: 1 second

0x2: 2 seconds

…

0x7: 7 seconds

0x8: 16 seconds

0x9: 18 seconds

…

0xE: 28 seconds

0xF: 60 seconds

Table 15

Capacitive Sensors Parameters

CapModeMisc

By default the ASI is using a common sensitivity for all capacitive sensors as in the usual case overlay material

and sensors sizes are about equal. The register bits CapSensitivity0_1[7:4] determine the sensitivity for all

sensors in common sensitivity mode.

In special applications it might be required to have a different, individual, sensitivity for each CAP pin. This can

be obtained by setting bit CapModeMisc[2]. The individual sensitivity mode results in longer sensing periods

than required in common sensitivity mode.

CapMode11_8, CapMode7_4, CapMode3_0:

The CAP pins can be set as a button, part of a slider or disabled depending on the application.

minimum default maximum

buttons zero six eight

slider one

(of four sensors) one

(of six sensors) one

(of twelve sensors)

Table 16 Possible

CAP pin modes

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Buttons and disabled CAP pins can be attributed freely (examples in Figure 46).

Figure 46

Button examples

Disabled CAP pins inside the slider sensor attribution sequence are allowed, but CAP buttons inside a slider

are not allowed (see example Figure 47 with CAP3 in a correct and a not allowed configuration).

Figure 47

Button and Slider good/bad configuration examples (I)

The physical order of the slider sensors on the PCB should correspond to the incremental CAP pin numbers.

Crossing slider PCB sensors and CAP number is not allowed. Figure 48 shows a valid configuration and a

wrong configuration where CAP5 andCAP6 are not routed correctly on the PCB.

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Figure 48

Button and Slider good/bad configuration examples (II)

The minimum position of the slider is associated to the CAP pin, attributed to the slider, with the lowest index

(in Figure 48 this is CAP2).

The maximum position of the slider is associated to the CAP pin, attributed to the slider, with the highest index

(in Figure 48 this is CAP6).

CapSensitivity0_1, CapSensitivity2_3, CapSensitivity4_5,

CapSensitivity6_7, CapSensitivity8_9, CapSensitivity10_11:

The sensitivity of the sensors can be set between 8 values. The higher the sensitivity is set the larger the value

of the ticks will be.

The minimum sensitivity can be used for thin overlay materials and large sensors, while the maximum

sensitivity is required for thicker overlay and smaller sensors.

The required sensitivity needs to be determined during a product development phase. Too low sensitivity

settings result in missing touches. Too high sensitivity settings will result in fault detection of fingers hovering

above the sensors.

The sensitivity is identical for all sensors in common sensitivity mode using the bits CapSensitivity0_1[7:4] and

can be set individually using register CapModeMisc[2].

The maximum number of ticks that can be obtained depends on the selected sensitivity as illustrated in Table

17.

Sensitivity Approximate

Maximum Tick Level

1000

1 2000

2 3000

3 4000

4 5000

5 6000

6 7000

7 8000

Table 17

ASI Maximum Tick Levels

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CapThresh0, CapThresh1, CapThresh2, CapThresh3, CapThresh4, CapThresh5, CapThresh6, CapThresh7,

CapThresh8, CapThresh9, CapThresh10, CapThresh11:

For each CAP pin a threshold level can be set individually.

The threshold levels are used by the SX8644 for making touch and release decisions on e.g. touch or no-

touch.

The details are explained in the sections for buttons and slider.

CapPerComp:

The SX8644 offers a periodic offset compensation for applications which are subject to substantial

environmental changes. The periodic offset compensation is done at a defined interval and only if slider and

buttons are released.

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5.4 Button Parameters

Button Parameters

Address Name Bits Description

7:6 Defines the buttons events reporting method.

00: Multiple reporting of all touches and releases (default)

01: Single reporting of the first button touch. Next button touches and releases are

ignored until release of the first button.

10: Reserved

11: Reserved

5:4 Defines the buttons interrupt (for all buttons)

00 : Interrupts masked

01 : Triggered on Touch

10 : Triggered on Release

11 : Triggered on Touch and Release (default)

3:2 Defines the number of samples at the scan period for determining a release

00: OFF, use incoming sample (default)

01: 2 samples debounce

10: 3 samples debounce

11: 4 samples debounce

0x21 BtnCfg

1:0 Defines the number of samples at the scan period for determining a touch

00: OFF, use incoming sample (default)

01: 2 samples debounce

10: 3 samples debounce

11: 4 samples debounce

0x22 BtnAvgThresh 7:0 Defines the positive threshold for disabling the processing filter averaging.

If ticks are above the threshold, then the averaging is suspended

0x00: 0

0x01: 4

…

0x50: 320 (default)

…

0xFF: 1020

0x23 BtnCompNegThresh 7:0 Defines the negative offset compensation threshold.

0x00: 0

0x01: 4

…

0x50: 320 (default)

…

0xFF: 1020

0x24 BtnCompNegCntMax

7:0 Defines the number of ticks (below the negative offset compensation threshold)

which will initiate an offset compensation.

0x00: Reserved

0x01: 1 sample (default)

…

0xFF-> samples

0x25 BtnHysteresis 7:0 Defines the button hysteresis corresponding to a percentage of the CAP thresholds

(defined in Table 18).

0x00: 0%

…

0x0A: 10% (default)

…

0x64: 100%

All buttons use the same hysteresis

0x26 BtnStuckAtTimeout 7:0 Defines the stuck at timeout.

0x00: OFF (default)

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Button Parameters

Address Name Bits Description

0x01: 1 second

…

0xFF: 255 seconds

Table 18

Button Configuration Parameters

A reliable button operation requires a coherent setting of the registers.

Figure 49 shows an example of a touch and a release. The ticks will vary slightly around the zero idle state.

When the touch occurs the ticks will rise sharply. At the release of the button the ticks will go down rapidly and

converge to the idle zero value.

ticks_diff

Figure 49 T

ouch and Release Example

As soon as the ticks become larger than the CAP thresholds (see registers of the previous section) plus the

hysteresis (defined in register BtnHysteresis) the debounce counter starts.

In the example of Figure 49 the touch is validated after 2 samples (BtnCfg [1:0] = 01).

The release is detected immediately (BtnCfg [3:2] = 00) at the first sample which is below the threshold minus the

hysteresis.

BtnCfg

The SX8644 can report all touches of multiple fingers or the SX8644 can be set to report only the first detected

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 SX8644 will count up to the number of debounce samples BtnCfg [1:0],

BtnCfg [3:2] before taking a touch or release decision. The sample period is identical to the scan period.

BtnAvgThresh

Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value.

In case the ticks get slightly positive this is considered as normal operation. Very large positive tick values

indicate a valid touch. The averaging filter is disabled as soon as the average reaches the value defined by

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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 SX8644 will start an

offset compensation procedure.

Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value.

In case the ticks get slightly negative this is considered as normal operation. However large negative values will

trigger an offset compensation phase and a new set of DCVs will be obtained.

The decision to trigger a compensation phase based on negative ticks is determined by the value in the register

BtnCompNegThresh and by the number of ticks below the negative thresholds defined in register

BtnCompNegCntMax. An example is shown in Figure 50.

ticks_diff

Figure 50

Negative Ticks Offset Compensation Trigger

BtnCompNegThresh

Small negative ticks are considered as normal operation and will occur very often.

Larger negative ticks however need to be avoided and a convenient method is to trigger an offset

compensation phase. The new set of DCV will assure the idle ticks will be close to zero again.

A trade-off has to be found for the value of this register. A negative threshold too close to zero will trigger a

compensation phase very often. A very negative threshold will never trigger.

BtnCompNegCntMax

As soon as the ticks get smaller than the Negative Threshold the Negative Counter starts to count.

If the counter goes beyond the Negative Counter Max then the offset compensation phase is triggered.

The recommended value for this register is ‘1’ which means that the offset compensation starts on the first tick

below the negative threshold.

BtnHysteresis

The hysteresis percentage is identical for all buttons.

A touch is detected if the ticks are getting larger as the value defined by:

CapThreshold + CapThreshold * hysteresis.

A release is detected if the ticks are getting smaller as the value defined by:

CapThreshold - CapThreshold * hysteresis.

BtnStuckAtTimeout

The stuckat timer can avoid sticky buttons.

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If the stuckat timer is set to one second then the touch of a finger will last only for one second and considered

released, even if the finger remains on the button for a longer time. After the actual finger release the button

can be touched again and will be reported as usual.

In case the stuckat timer is not required it can be set to zero.

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5.5 Slider Parameters

Slider Parameters

Address Name Bits Description

7:4 Reserved

3:2 Defines the number of samples at the scan period for determining a release

00: OFF, use incoming sample (default)

01: 2 samples debounce

10: 3 samples debounce

11: 4 samples debounce

0x27 SldCfg

1:0 Defines the number of samples at the scan period for determining a touch

00: OFF, use incoming sample (default)

01: 2 samples debounce

10: 3 samples debounce

11: 4 samples debounce

0x28 SldStuckAtTimeout 7:0 Defines the stuck at timeout.

0x00: OFF (default)

0x01: 1 second

…

0xFF: 255 seconds

0x29 SldHysteresis 7:0 Defines the Slider Touch/Release Hysteresis.

0x00: 0

0x01: 4

…

0x03: 12 (default)

…

0xFF: 1020

0x2B SldNormMsb 7:0 Slider Norm Msb

0x2C SldNormLsb 7:0 Slider Norm Lsb

Defines the 16 bits slider norm (default 0x0180)

0x2D SldAvgThresh 7:0 Defines the positive threshold for disabling the processing filter averaging.

If ticks are above the threshold, then the averaging is suspended

0x00: 0

0x01: 4

…

0x50: 320 (default)

…

0xFF: 1020

0x2E SldCompNegThresh 7:0 Defines the negative offset compensation threshold.

0x00: 0

0x01: 4

…

0x50: 320 (default)

…

0xFF: 1020

0x2F SldCompNegCntMax

7:0 Defines the number of ticks (below the negative offset compensation threshold)

which will initiate an offset compensation.

0x00: Reserved

0x01: 1 sample (default)

…

0xFF: 255 samples

0x30 SldMoveThresh 7:0 Defines the threshold for detecting a move high or move low.

The threshold is a percentage of the maximum slider position.

0x00: 0%

…

0x02: 2% (default)

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Slider Parameters

Address Name Bits Description

…

0x64: 100%

A succeeding position difference, at the scan period, above the threshold is

considered as a move high or move low.

Table 19

Slider Parameters

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The pressure represents the finger touch on the sensors of the slider and it used to determine if a slider is

touched or released.

∑

−

−=

))()(_(

iCapThreshidifftickseSldPressur

- N is the number of sensors,

- A sensor with ticks smaller than the CapThreshold is not taken into account for calculating the pressure

In case the pressure equals zero the slider status is released.

In case the pressure is larger as the Slider

Hysteresis

the slider status is touched.

The position of a finger on a slider is calculated by the centre of gravity algorithm.

∑

−

∗=

))()(_(

))()(_(*

iCapThreshidiffticks

iCapThreshidiffticksi

SldNorm

SldPos

- N is the number of sensors,

- A sensor with ticks smaller than the CapThreshold is not taken into account for calculating the position,

- SldNorm[15:0] is a 16 bit number determined by SldNormMsb[15:8] and SldNormLsb[7:0].

- SldPos is the slider position (16 bits) which can be read by the host over the I2C registers SldPosMsb and

SldPosLsb

Figure 51

Slider Position

Figure 51 shows an example of a slider composed of 6 sensors (CAP0, CAP1… CAP5).

The default slider norm value 12 (SldNormMsb = 0x01, SldNormLsb = 0x80), is taken for the example.

A touch on CAP0 gives the slider position: 0.

A touch on CAP1 gives the slider position: 12.

A touch on CAP5 gives the slider position: 60.

If a touch occurs on CAP0 and CAP1 the centre of gravity algorithm will interpolate.

Assuming the touch is identically distributed on CAP0 and CAP1 then the position will be: 6

Assuming the touch is identically distributed on CAP1 and CAP2 then the position will be: 18

Assuming the touch is identically distributed on CAP4 and CAP5 then the position will be: 54

The maximum slider position (for this example) that can be obtained is 60.

The minimum position of a slider equals 0.

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The maximum position (SldPosMax) is defined by:

( )

−×= N

SldNorm

SldPosMax

with:

N is the number of sensors in the slider

Slow varying slider ticks due to environmental changes are handled as buttons in the previous section.

If the ticks pass below the slider negative threshold for more than the compensation negative max counter then an

offset compensation phase will be triggered.

If the ticks pass above the slider average positive threshold then the averaging filters will be held.

A finger that moves very slowly over the slider is not considered as a movement. The status move low and move

high will not be set.

A finger that moves faster on the slider will change the movement status.

A movement is detected if the difference of the position for two succeeding samples at the scanning rate goes

beyond the movement threshold (SldMoveThresh). A large movement threshold requires very rapid finger

movements, while a small movement threshold detects more easily movements but gets sensitive to noise

variations as well.

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5.6 Mapping Parameters

Mapping Parameters

Address Name Bits Description

7:3 Reserved 0x33 MapWakeupSize

2:0 Doze -> Active wake up sequence size.

0: Any sensor event (default)

1: key0

2: key0, key1

…

6: key0, key1,…key5

7: No sensor event, only GPI or I2C cmd can exit Doze mode

Each key must be followed by a release to be validated.

Any other sensor event before the release is ignored.

Any wrong key implies the whole sequence to be entered again.

7:4 key5 0x34 MapWakeupValue0

3:0 key4

7:4 key3 0x35 MapWakeupValue1

3:0 key2

7:4 key1 0x36 MapWakeupValue2

3:0 key0

Defines the sensor event associated to each key.

0x00: Btn0 (default)

0x01: Btn1

…

0x0B: Btn11

0x0C: Slider Touch

0x0D: Move Low

0x0E: Move High

0x0F: Reserved

7:4 GPIO[7] 0x37 MapAutoLight0

3:0 GPIO[6]

7:4 GPIO[5] 0x38 MapAutoLight1

3:0 GPIO[4]

7:4 GPIO[3] 0x39 MapAutoLight2

3:0 GPIO[2]

7:4 GPIO[1] 0x3A MapAutoLight3

3:0 GPIO[0]

Defines the mapping between GPOs (with

Autolight ON) and sensor events.

0x00: Btn0 (default)

0x01: Btn1

…

0x0B: Btn11

0x0C: Group0 as defined by MapAutoLightGrp0

0x0D: Group1 as defined by MapAutoLightGrp1

0x0E: Move Low

0x0F: Move High

Several GPOs can be mapped to the same sensor

event and will be controlled simultaneously.

7 Reserved

6 Segment

5 Move High

4 Move Low

3 Btn11

2 Btn10

1 Btn9

0x3B MapAutoLightGrp0Msb

0 Btn8

7 Btn7

6 Btn6

5 Btn5

4 Btn4

0x3C MapAutoLightGrp0Lsb

3 Btn3

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 except slider event Segment

which is exclusive (ie must be the only one

enabled to be used)

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Mapping Parameters

Address Name Bits Description

2 Btn2

1 Btn1

0 Btn0

7 Reserved

6 Slider Touch

5 Move High

4 Move Low

3 Btn11

2 Btn10

1 Btn9

0x3D MapAutoLightGrp1Msb

0 Btn8

7 Btn7

6 Btn6

5 Btn5

4 Btn4

3 Btn3

2 Btn2

1 Btn1

0x3E MapAutoLightGrp1Lsb

0 Btn0

Defines Group1 sensor events:

0: OFF (default)

1: ON

If any of the enabled sensor events occurs the

Group0 event will occur as well.

All sensors events within the group can be

independently set.

0x3F MapSegmentHysteresis 7:0 Defines the position hysteresis for detecting a segment change.

The hysteresis is defined as a percentage of the maximum slider position.

0x00: 0%

…

0x02: 2% (default)

…

0x64: 100%

This hysteresis applies to all segments of the slider.

Table 20

Mapping Parameters

MapWakeupSize

The number of keys defining the wakeup sequence can be set from 1 to 6.

If the size is set to 0 then wakeup is done on any sensor event.

if the size is set to 6 then wakeup is done only by GPI or an I2C command.

MapWakeupValue0, MapWakeupValue1, MapWakeupValue2

For the wakeup sequence Btn2 -> Btn5 -> Btn6 ->Btn0 the required register settings are:

- MapWakeupSize set to 0x04,

- key0 = 0x2

- key1 = 0x5

=> MapWakeupValue2 set to 0x52

- key2 = 0x6

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- key3 = 0x0

=> MapWakeupValue2 set to 0x06

MapAutoLight0, MapAutoLight1, MapAutoLight2, MapAutoLight3

MapAutoLightGrp0Msb, MapAutoLightGrp0Lsb, MapAutoLightGrp1Msb, MapAutoLightGrp1Lsb

These registers define the mapping between the GPO pins

(with Autolight ON)

and the sensor information which

will control its ON/OFF state.

The mapping can be done to a specific sensor event but also on groups (in this case any sensor event in the

group will control the GPO).

Table 21 defines for each selectable sensor event, which action will trigger corresponding GPO to switch ON

or OFF.

MapAutoLight GPO ON GPO OFF

BtnX Touch Release

Slider Touch Touch Release

Slider Move High Move High Move Low or Release

Slider Move Low Move Low Move High or Release

Slider Segment Segment Touched Segment Released

Table 21

Autolight Mapping, Sensor Information

Examples:

- If GPO[0] should change state accordingly to Btn4 then MapAutoLight3[3:0] should be set to 0x04.

- If GPO[0] should change state accordingly to Btn0 or Btn1 then Group0 can be used as following:

- MapAutoLight3[3:0] should be set to 0x0C (ie Group0).

- MapAutoLightGrp0 should be set to 0x0003 (ie Btn0 or Btn1)

When the Slider Segment event is mapped, the number of GPOs mapped to it determines the number of slider

segments. The GPO with the lowest pin index is mapped on the segment with the smallest positions.

E.g. if two GPOs (e.g.GPO[0] and GPO[1]) are mapped to the Slider Segment event then the slider is split in

two segments. GPO[0] will turn ON for a touch on the slider segment [0, SldPosMax/2] and GPO[1] for a touch

on the slider segment [SldPosMax/2, SldPosMax].

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5.7 GPIO Parameters

GPIO Parameters

Address Name Bits

Description

7:6 GPIO[7] Mode

5:4 GPIO[6] Mode

3:2 GPIO[5] Mode

0x40 GpioMode7_4

1:0 GPIO[4] Mode

7:6 GPIO[3] Mode

5:4 GPIO[2] Mode

3:2 GPIO[1] Mode

0x41 GpioMode3_0

1:0 GPIO[0] Mode

Defines the GPIO mode.

00: GPO (default)

01: GPP

10: GPI

11: Reserved

GPIO[7] Output Value at Power Up

GPIO[6] Output Value at Power Up

GPIO[5] Output Value at Power Up

GPIO[4] Output Value at Power Up

GPIO[3] Output Value at Power Up

GPIO[2] Output Value at Power Up

GPIO[1] Output Value at Power Up

0x42 GpioOutPwrUp 7:0

GPIO[0] Output Value at Power Up

Defines the values of GPO and GPP pins

after power up ie default values of I2C

parameters GpoCtrl and GppIntensity

respectively.

0: OFF(GPO) / IntensityOff (GPP) (default)

1: ON (GPO) / IntensityOn (GPP)

Bits corresponding to GPO pins with

Autolight ON should be left to 0.

Before being actually initialized GPIOs are

set as inputs with pull up.

GPIO[7] AutoLight

GPIO[6] AutoLight

GPIO[5] AutoLight

GPIO[4] AutoLight

GPIO[3] AutoLight

GPIO[2] AutoLight

GPIO[1] AutoLight

0x43 GpioAutoLight 7:0

GPIO[0] AutoLight

Enables Autolight in GPO mode

0 : OFF

1 : ON (default)

GPIO[7] Output Polarity

GPIO[6] Output Polarity

GPIO[5] Output Polarity

GPIO[4] Output Polarity

GPIO[3] Output Polarity

GPIO[2] Output Polarity

GPIO[1] Output Polarity

0x44 GpioPolarity 7:0

GPIO[0] Output Polarity

Defines the polarity of the GPO and GPP

pins.

0: Inverted (default)

1: Normal

0x45 GpioIntensityOn0

0x46 GpioIntensityOn1

0x47 GpioIntensityOn2

7:0 ON Intensity Index

Defines the ON intensity index

0x00: 0

0x01: 1

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GPIO Parameters

Address Name Bits

Description

0x48 GpioIntensityOn3

0x49 GpioIntensityOn4

0x4A GpioIntensityOn5

0x4B GpioIntensityOn6

0x4C GpioIntensityOn7

…

0xFF: 255 (default)

0x4D GpioIntensityOff0

0x4E GpioIntensityOff1

0x4F GpioIntensityOff2

0x50 GpioIntensityOff3

0x51 GpioIntensityOff4

0x52 GpioIntensityOff5

0x53 GpioIntensityOff6

0x54 GpioIntensityOff7

7:0 OFF Intensity Index

Defines the OFF intensity index

0x00: 0 (default)

0x01: 1

…

0xFF: 255

GPIO[7] Function

GPIO[6] Function

GPIO[5] Function

GPIO[4] Function

GPIO[3] Function

GPIO[2] Function

GPIO[1] Function

0x56 GpioFunction 7:0

GPIO[0] Function

Defines the intensity index vs PWM pulse

width function.

0: Logarithmic (default)

1: Linear

GPIO[7] Fading Increment Factor

GPIO[6] Fading Increment Factor

GPIO[5] Fading Increment Factor

GPIO[4] Fading Increment Factor

GPIO[3] Fading Increment Factor

GPIO[2] Fading Increment Factor

GPIO[1] Fading Increment Factor

0x57 GpioIncFactor 7:0

GPIO[0] Fading Increment Factor

Defines the fading increment factor.

0: 1, intensity index incremented every

increment time (default)

1: 16, intensity index incremented every 16

increment times

GPIO[7] Fading Decrement Factor

GPIO[6] Fading Decrement Factor

GPIO[5] Fading Decrement Factor

GPIO[4] Fading Decrement Factor

GPIO[3] Fading Decrement Factor

GPIO[2] Fading Decrement Factor

GPIO[1] Fading Decrement Factor

0x58 GpioDecFactor 7:0

GPIO[0] Fading Decrement Factor

Defines the fading decrement factor.

0: 1, intensity index decremented every

decrement time (default)

1: 16, intensity index decremented every 16

decrement times

0x59 GpioIncTime7_6 7:4 GPIO[7] Fading Increment Time Defines the fading increment time.

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GPIO Parameters

Address Name Bits

Description

3:0 GPIO[6] Fading Increment Time

7:4 GPIO[5] Fading Increment Time 0x5A GpioIncTime5_4

3:0 GPIO[4] Fading Increment Time

7:4 GPIO[3] Fading Increment Time 0x5B GpioIncTime3_2

3:0 GPIO[2] Fading Increment Time

7:4 GPIO[1] Fading Increment Time 0x5C GpioIncTime1_0

3:0 GPIO[0] Fading Increment Time

0x0: OFF (default)

0x1: 0.5ms

0x2: 1ms

…

0xF: 7.5ms

The total fading in time will be:

GpioIncTime*GpioIncFactor*

(GpioIntensityOn – GpioIntensityOff)

7:4 GPIO[7] Fading Decrement Time 0x5D GpioDecTime7_6

3:0 GPIO[6] Fading Decrement Time

7:4 GPIO[5] Fading Decrement Time 0x5E GpioDecTime5_4

3:0 GPIO[4] Fading Decrement Time

7:4 GPIO[3] Fading Decrement Time 0x5F GpioDecTime3_2

3:0 GPIO[2] Fading Decrement Time

7:4 GPIO[1] Fading Decrement Time 0x60

GpioDecTime1_0

3:0 GPIO[0] Fading Decrement Time

Defines the fading decrement time.

0x0: OFF

0x1: 0.5ms

0x2: 1ms

…

0x4: 2.0ms (default)

…

0xF: 7.5ms

The total fading out time will be:

GpioDecTime*GpioDecFactor*

(GpioIntensityOn – GpioIntensityOff)

7:4 GPIO[7] OFF Delay 0x61 GpioOffDelay7_6

3:0 GPIO[6] OFF Delay

7:4 GPIO[5] OFF Delay 0x62 GpioOffDelay5_4

3:0 GPIO[4] OFF Delay

7:4 GPIO[3] OFF Delay 0x63 GpioOffDelay3_2

3:0 GPIO[2] OFF Delay

7:4 GPIO[1] OFF Delay 0x64 GpioOffDelay1_0

3:0 GPIO[0] OFF Delay

Defines the delay after GPO OFF trigger

before fading out starts.

0x0: OFF (default)

0x1: 200ms

0x2: 400ms

…

0xF: 3000ms

7:6 GPIO[7] Pullup/down

5:4 GPIO[6] Pullup/down

3:2 GPIO[5] Pullup/down

0x65 GpioPullUpDown7_4

1:0 GPIO[4] Pullup/down

7:6 GPIO[3] Pullup/down

5:4 GPIO[2] Pullup/down

3:2 GPIO[1] Pullup/down

0x66 GpioPullUpDown3_0

1:0 GPIO[0] Pullup/down

Enables pullup/down resistors for GPI pins.

00 : None (default)

01 : Pullup

10 : Pulldown

11 : Reserved

7:6 GPI[7] Interrupt

5:4 GPI[6] Interrupt

3:2 GPI[5] Interrupt

0x67 GpioInterrupt7_4

1:0 GPI[4] Interrupt

7:6 GPI[3] Interrupt

5:4 GPI[2] Interrupt

0x68 GpioInterrupt3_0

3:2 GPI[1] Interrupt

Defines the GPI edge which will trigger INTB

falling edge and exit Sleep/Doze modes if

relevant.

00 : None (default)

01 : Rising

10 : Falling

11 : Both

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GPIO Parameters

Address Name Bits

Description

1:0 GPI[0] Interrupt

GPI[7] Debounce

GPI[6] Debounce

GPI[5] Debounce

GPI[4] Debounce

GPI[3] Debounce

GPI[2] Debounce

GPI[1] Debounce

0x69 GpioDebounce 7:0

GPI[0] Debounce

Enables the GPI debounce (done on 10

consecutive samples at 1ms).

0 : OFF (default)

1 : ON

Table 22

GPIO Parameters

Table 23 resumes the applicable SPM and I2C parameters for each GPIO mode.

GPI GPP GPO

GpioMode X X X

GpioOutPwrUp X

GpioAutoligth X

GpioPolarity X X

GpioIntensityOn X

GpioIntensityOff X

GpioFunction X X

GpioIncFactor X

GpioDecFactor X

GpioIncTime X

GpioDecTime X

GpioOffDelay X

GpioPullUpDown X

GpioInterrupt X

SPM

GpioDebounce X

IrqSrc[4] X

GpiStat X

GpoCtrl X

GppPinId X

I2C

GppIntensity X

At power up, GppIntensity of each GPP pin is initialized with GpioIntensityOn or GpioIntensityOff depending on GpioOutPwrUp

corresponding bits value.

Only if Autolight is OFF, else must be left to 0 (default value)

Only if Autolight is OFF, else ignored

Table 23

Applicable SPM/I2C Parameters vs. GPIO Mode

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6 I2C

NTERFACE

The I2C implemented on the SX8644 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). These registers give information about the status of the capacitive buttons, slider, GPIs, operation

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 SX8644 is powered down.

The SPM can be stored permanently in the NVM memory of the SX8644. The SPM gateway communication 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 52.

After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The

SX8644 then Acknowledges [A] that it is being addressed, and the Master sends an 8 bit Data Byte consisting of

the SX8644 Register Address (RA). The Slave Acknowledges [A] and the master sends the appropriate 8 bit Data

Byte (WD0). Again the Slave Acknowledges [A]. In case the master needs to write more data, a succeeding 8 bit

Data Byte will follow (WD1), acknowledged by the slave [A]. This sequence will be repeated until the master

terminates the transfer with the Stop condition [P].

Figure 52

I2C write

The register address is incremented automatically when successive register data (WD1...WDn) is supplied by the

master.

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6.2 I2C read

The format of the I2C read is given in Figure 53.

After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The

SX8644 then Acknowledges [A] that it is being addressed, and the Master responds with an 8 bit Data consisting

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 SX8644 responds with an Acknowledge [A] and the read Data byte (RD0). If the master needs to read more

data it will acknowledge [A] and the SX8644 will send the next read byte (RD1). This sequence can be repeated

until the master terminates with a NACK [N] followed by a stop [P].

Figure 53

I2C read

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6.3 I2C Registers Overview

Address Name R/W Description

0x00 IrqSrc read Interrupt Source

0x01 CapStatMsb read Slider/Button Status MSB

0x02 CapStatLsb read Button Status LSB

0x03 SldPosMsb read Slider Position MSB

0x04 SldPosLsb read Slider Position LSB

0x05 Reserved

0x06 Reserved

0x07 GpiStat read GPI Status

0x08 SpmStat read SPM Status

0x09 CompOpMode read/write Compensation and

Operating Mode

0x0A GpoCtrl read/write GPO Control

0x0B GppPinId read/write GPP Pin Selection

0x0C GppIntensity read/write GPP Intensity

0x0D SpmCfg read/write SPM Configuration

0x0E SpmBaseAddr read/write SPM Base Address

0x0F Reserved

0xAC SpmKeyMsb read/write SPM Key MSB

0xAD SpmkeyLsb read/write SPM Key LSB

0xB1 SoftReset read/write Software Reset

Table 24

I2C Registers Overview

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6.4 Status Registers

Address Name Bits Description

7 Reserved

6 NVM burn interrupt flag

5 SPM write interrupt flag

4 GPI interrupt flag

3 Slider interrupt flag

2 Buttons interrupt flag

1 Compensation interrupt flag

0x00 IrqSrc

0 Operating Mode interrupt flag

Interrupt source flags

0: Inactive (default)

1: Active

INTB goes low if any of

these bits is set.

More than one bit can be

set.

Reading IrqSrc clears it

together with INTB.

Table 25

Interrupt Source

The delay between the actual event and the flags indicating the interrupt source may be one scan period.

IrqSrc[6] is set once NVM burn procedure is completed.

IrqSrc[5] is set once SPM write is effective.

IrqSrc[4] is set if a GPI edge as programmed in GpioInterrupt occurred. GpiStat shows the detailed status of the

GPI pins.

IrqSrc[3] is set if a Slider event occurred (touch, release, move high, move low or position change) . CapStatMsb,

SldPosMsb and SldPosLsb show the detailed status of the Slider.

IrqSrc[2] is set if a Button event occurred (touch or release if enabled). CapStatMsb and CapStatLsb show the

detailed status of the Buttons.

IrqSrc[1] is set once compensation procedure is completed either through automatic trigger or via host request.

IrqSrc[0] is set when actually entering Active or Doze mode either through automatic wakeup or via host request.

CompOpmode shows the current operation mode.

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Address Name Bits Description

7 Reserved

6 Slider Move High

5 Slider Move Low

Slider Move status

0: No move (default)

1: Move

The status remains high as long as the slider is

touched and no opposite move has occurred.

4 Slider Touched Slider Touch status

0: Released (default)

1: Touched

3 Button 11 Touched

2 Button 10 Touched

1 Button 9 Touched

0x01 CapStatMsb

0 Button 8 Touched

7 Button 7 Touched

6 Button 6 Touched

5 Button 5 Touched

4 Button 4 Touched

3 Button 3 Touched

2 Button 2 Touched

1 Button 1 Touched

0x02 CapStatLsb

0 Button 0 Touched

Button Touch status

0: Released (default)

1: Touched

Table 26 Slider,

Button status MSB/LSB

Address Name Bits Description

0x03 SldPosMsb 7:0 Slider Position[15:8]

0x04 SldPosLsb 7:0 Slider Position[7:0]

Shows the current (touched) or last (released)

slider position[15:0] unsigned (default 0x00)

Table 27

Slider position MSB/LSB

Address Name Bits Description

0x07 GpiStat 7:0 GPI[7:0]

Status

Status of each individual GPI pin

0: Low

1: High

Bits of non-GPI pins are set to 0.

Table 28

I2C GPI status

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Address Name Bits Description

7:4 reserved

3 NvmValid Indicates if the current NVM is valid.

0: No – QSM is used

1: Yes – NVM is used

0x08 SpmStat

2:0 NvmCount

Indicates the number of times NVM has been burned:

0: None – QSM is used (default)

1: Once – NVM is used if NvmValid = 1, else QSM.

2: Twice – NVM is used if NvmValid = 1, else QSM.

3: Three times – NVM is used if NvmValid = 1, else QSM.

4: More than three times – QSM is used

Table 29

I2C SPM status

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6.5 Control Registers

Address Name Bits Description

7:3 Reserved*, write only ‘00000’

2 Compensation Indicates/triggers compensation procedure

0: Compensation completed (default)

1: read -> compensation running ; write -> trigger

compensation

0x09 CompOpMode

1:0 Operating Mode

Indicates/programs** operating mode

00: Active mode (default)

01: Doze mode

10: Sleep mode

11: Reserved

Table 30

I2C compensation, operation modes

* The reading of these reserved bits will return varying values.

** After the operating mode change (Active/Doze) the host should wait for INTB or 300ms before

performing any I2C read access.

Address Name Bits Description

0x0A GpoCtrl 7:0 GpoCtrl[7:0]

Triggers ON/OFF state of GPOs when Autolight is

OFF

0: OFF (ie go to IntensityOff)

1: ON (ie go to IntensityOn)

Default is set by SPM parameter GpioOutPwrUp

Bits of non-GPO pins are ignored.

Table 31

I2C GPO Control

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Address Name Bits Description

7:3 Reserved, write only ‘00000’

0x0B GppPinId 2:0 GPP Pin Identifier

Defines the GPP pin to which the GppIntensity is

assigned for the following read/write operations

0x0 = GPP0 (default)

0x1 = GPP1

...

0x7 = GPP7

GPPx refers to pin GPIOx configured as GPP

Table 32

I2C GPP Pin Identifier

Address Name Bits Description

0x0C GppIntensity 7:0

Defines the intensity index of the GPP pin selected in GppPinId

0x00: 0

0x01: 1

…

0xFF: 255

Reading returns the intensity index of the GPP pin selected in GppPinId.

Default value is IntensityOn or IntensityOff depending on GpioOutPwrUp.

Table 33

I2C GPP Intensity

Address Name Bits Description

0xB1 SoftReset 7:0 Writing 0xDE followed by 0x00 will reset the chip.

Table 34 I2C

Soft Reset

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6.6 SPM Gateway Registers

The SX8644 I2C interface offers two registers for exchanging the SPM data with the host.

• SpmCfg

• SpmBaseAddr

Address Name Bits Description

7:6 00: Reserved

5:4

Enables I2C SPM mode

00: OFF (default)

01: ON

10: Reserved

11: Reserved

3 Defines r/w direction of SPM

0: SPM write access (default)

1: SPM read access

0x0D SpmCfg

2:0 000: Reserved

Table 35

SPM access configuration

Address

Name Bits Description

0x0E SpmBaseAddr 7:0 SPM Base Address (modulo 8).

The lowest address is 0x00 (default).

The highest address is 0x78.

Table 36 SPM Base Address

The exchange of data, read and write, between the host and the SPM is always done in bursts of eight bytes.

The base address of each burst of eight bytes is a modulo 8 number, starting at 0x00 and ending at 0x78.

The registers SpmKeyMsb and SpmKeyLsb are required for NVM programming as described in section 6.7.

Address Name Bits Description

0xAC SpmKeyMsb 7:0 SPM to NVM burn Key MSB Unlock requires writing data: 0x62

Table 37

SPM Key MSB

Address Name Bits Description

0xAD SpmKeyLsb 7:0 SPM to NVM burn Key LSB Unlock requires writing data: 0x9D

Table 38

SPM Key LSB

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6.6.1 SPM Write Sequence

The SPM write can be done in any mode (Active, Doze, Sleep). Writing the SPM in Sleep is useful to avoid

potential transient behaviors.

The SPM must always be written in blocks of 8 bytes. The sequence is described below:

1. Set the I2C in SPM mode by writing “01” to SpmCfg[5:4] and SPM write access by writing ‘0’ to SpmCfg[3].

2. Write the SPM base address to SpmBaseAddr (The base address needs to be a value modulo 8).

3. Write the eight consecutive bytes to I2C address 0, 1, 2, …7

4. Terminate by writing “000” to SpmCfg[5:3].

Figure 54: SPM Write Sequence

The complete SPM can be written by repeating 16 times the cycles shown in Figure 54 using base addresses

0x00, 0x08, 0x10, …, 0x70, 0x78. Between each sequence the host should wait for INTB (Active/Doze) or 30ms

in Sleep.

In Active or Doze mode, once the SPM write sequence is actually applied, the INTB pin will be asserted and

IrqSrc[5] set. In Sleep mode the SPM write can be actually applied with a delay of 30ms.

The host clears the interrupt and IrqSrc[5] by reading the IrqSrc register.

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6.6.2 SPM Read Sequence

The SPM read can be done in any mode (Active, Doze, Sleep).

The SPM must always be read in blocks of 8 bytes. The sequence is described below:

1. Set the I2C in SPM mode by writing “01” to SpmCfg[5:4] and SPM read access by writing ‘1’ to SpmCfg[3].

2. Write the SPM base address to SpmBaseAddr (The base address needs to be a value modulo 8).

3. Read the eight consecutive bytes from I2C address 0, 1, 2, …7

4. Terminate by writing “000” to SpmCfg[5:3].

Figure 55: SPM Read Sequence

The complete SPM can be read by repeating 16 times the cycles shown in Figure 55 using base addresses 0x00,

0x08, 0x10, …, 0x70, 0x78.

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6.7 NVM burn

The content of the SPM can be copied permanently (burned) into the NVM to be used as the new default

parameters. The burning of the NVM can be done up to three times and must be done only when the SPM is

completely written with the desired data. The NVM burn must be done in Active or Doze mode.

Once the NVM burn process is terminated IrqSrc[6] will be set and INTB asserted.

After a reset the burned NVM parameters will be copied into the SPM.

The number of times the NVM has been burned can be monitored by reading NvmCount from the I2C register

SpmStat[2:0].

Figure 56

Simplified Diagram NvmCount

Figure 56 shows the simplified diagram of the NVM counter. The SX8644 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 SX8644 switches definitely to the QSM.

The burning of the SPM into the NVM is done by executing a special sequence of four I2C commands.

1. Write the data 0x62 to the I2C register I2CKeyMsb. Terminate the I2C write by a STOP.

2. Write the data 0x9D to the I2C register I2CKeyLsb. Terminate the I2C write by a STOP.

3. Write the data 0xA5 to the I2C register I2CSpmBaseAddr. Terminate the I2C write by a STOP.

4. Write the data 0x5A to the I2C register I2CSpmBaseAddr. Terminate the I2C write by a STOP.

This is illustrated in Figure 57.

S SA 0 0x0EA 0xA5A PA

S : Start condition

SA : Slave address

A : Slave acknowledge

P : Stop condition

From master to slave

From slave to master

S SA 0 0x0EA 0x5AA PA

S SA 0 0xAC

A0x62A PA

S SA 0 0xADA 0x9DA PA

Figure 57: NVM burn procedure

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7 A

PPLICATION

NFORMATION

A typical application schematic is shown in Figure 58.

Figure 58

Typical Application

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8 P

ACKAGING

NFORMATION

8.1 Package Outline Drawing

SX8644 is assembled in a MLPQ-W32 package as shown in Figure 59.

Figure 59

Package Outline Drawing

8.2 Land Pattern

The land pattern of MLPQ-W32 package, 5 mm x 5 mm is shown in Figure 60.

Figure 60

Land Pattern

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ONTACT INFORMATION

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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.

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Wireless and Sensing Products Division

200 Flynn Road, Camarillo, CA 93012

Phone: (805) 498-2111 Fax: (805) 498-3804

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