SX8661I07AULTRT - SEMTECH - Datasheet.Live

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SX8661

Low Power, Capacitive Button Touch and Proximity Controller

(8 sensors) with LED Drivers and Analog Output

GENERAL DESCRIPTION

The SX8661 is an ultra low power, fully integrated 8-

channel solution for capacitive touch-button and

proximity detection applications. Unlike many

capacitive touch solutions, the SX8661 features

dedicated capacitive sense inputs (that requires no

external components) in addition to 8 general

purpose I/O ports (GPIO). Each of the 8 on-chip

GPIO/LED driver is equipped with independent PWM

source for enhanced visual effect such as dimming,

and breathing.

The SX8661 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 SX8661 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 SX8661 supports the 400 kHz I²C serial bus

data protocol and includes a field programmable

slave address. The tiny 4mm x 4mm footprint makes

it an ideal solution for portable, battery powered

applications where power and density are at a

premium.

TYPICAL APPLICATION CIRCUIT

KEY PRODUCT FEATURES

 Complete 8 Sensors Capacitive Touch-Button Solution

o Up to 8 LED Drivers for individual Visual Feedback with

Auto Lightening

o Configurable Single or Continuous Fading Mode

o 256 steps PWM Linear and Logarithmic control

 Proximity Sensing up to several centimetres

 High Resolution Capacitive Sensing

o Up to 100pF of Offset Cap. Compensation at Full

Sensitivity

o Capable of Sensing up thru 5mm thick Overlay Materials

 Up to 2 Analog Output Interfaces (AOI-A and AOI-B)

o Enable button detection thru host’s ADC

 Support of buzzer for audible feedback

 User-selectable Button Reporting Configuration

o Report Single or Report Strongest

 Extremely Low Power

o 8uA (typ) in Sleep Mode

o 70uA (typ) in Doze Mode (195ms)

o 200uA (typ) in Active Mode (30ms)

 Programmable Scanning Period from 15ms to several seconds

 Auto Offset Compensation

o Eliminates false triggers due to environmental factors

(temperature, humidity)

o Initiated on power-up and configurable intervals

 Multi-Time In-Field Programmable Firmware Parameters

for Ultimate Flexibility

o On-chip user programmable memory for fast, self

contained start-up

 No External Components per Sensor Input

 Internal Clock Requires No External Components

 Differential Sensor Sampling for Reduced EMI

 Optional 400 KHz I²C Interface with Programmable Address

 -40°C to +85°C Operation

APPLICATIONS

 LCD TVs, Monitors

 White Goods

 Notebook/Netbook/Portable/Handheld computers

 Consumer Products, Instrumentation, Automotive

 Mechanical Button Replacement

ORDERING INFORMATION

Part Number Temperature

Range Package

SX8661I07AULTRT1-40°C to +85°C Lead Free MLPQ-UT28

1 3000 Units/reel

* This device is RoHS/WEEE compliant and Halogen Free

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SX8661

Low Power, Capacitive Button Touch and Proximity Controller

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Table of Contents

GENERAL DESCRIPTION........................................................................................................................1

TYPICAL APPLICATION CIRCUIT............................................................................................................1

KEY PRODUCT FEATURES.....................................................................................................................1

APPLICATIONS.......................................................................................................................................1

ORDERING INFORMATION......................................................................................................................1

1 GENERAL DESCRIPTION...............................................................................................................5

1.1 Pin Diagram 5

1.2 Marking information 5

1.3 Pin Description 6

1.4 Simplified Block Diag ram 7

1.5 Acronyms 7

2 ELECTRICAL CHARACTERISTICS .................................................................................................8

2.1 Absolute Maximum Ratings 8

2.2 Recommended Operating Conditions 8

2.3 Thermal Characteristics 8

2.4 Electrical Specifications 9

3 FUNCTIONAL DESCRIPTION........................................................................................................12

3.1 Quickst art Application 12

3.2 Introduction 14

3.2.1 General 14

3.2.2 GPIOs 14

3.2.3 Analog Output Interface A and B (SPO mode) 14

3.2.4 Buzzer (SPO mode) 14

3.2.5 Parameters 14

3.2.6 Configuration 15

3.3 Scan Pe rio d 15

3.4 Operation modes 15

3.5 Sensors on the PCB 16

3.6 Button Information 17

3.7 Buzzer 17

3.8 Analog Output Interface 19

3.9 Analog Sensing Interface 21

3.10 Offset Compensation 23

3.11 Processing 24

3.12 Configuration 24

3.13 Power Management 26

3.14 Clock Circuitry 26

3.15 I2C interface 26

3.16 Interrupt 27

3.16.1 Power up 27

3.16.2 Assertion 27

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3.16.3 Clearing 27

3.16.4 Example 28

3.17 Reset 28

3.17.1 Power up 28

3.17.2 RESETB 29

3.17.3 Software Reset 29

3.18 General Purpose Input and Outputs 30

3.18.1 GPP mode 30

3.18.2 GPO Dual Reporting 32

3.18.3 GPO Fading 33

3.18.4 Intensity index vs PWM pulse width 34

3.18.5 GPO Triple Reporting 35

4 PIN DESCRIPTIONS.....................................................................................................................37

4.1 Introduction 37

4.2 ASI pins 37

4.3 Host interface pins 38

4.4 Power management pins 41

4.5 General purpose IO pins 42

5 DETAILED CONFIGURATION DESCRIPTIONS ..............................................................................43

5.1 Introduction 43

5.2 General Parameters 46

5.3 Capacitiv e Sen sors Paramet ers 47

5.4 Proxi m it y Param et e rs 51

5.5 Button Parameters 53

5.6 Analog Output Interface Parameters 59

5.7 Buzzer Parameters 61

5.8 Mapping Parameters 62

5.9 GPIO Parameters 64

6 I2C INTERFACE...........................................................................................................................68

6.1 I2C Write 68

6.2 I2C read 69

6.3 I2C Registers Overview 70

6.4 Status Registers 71

6.5 Control Registers 73

6.6 SPM Gateway Registers 75

6.6.1 SPM Write Sequence 76

6.6.2 SPM Read Sequence 77

6.7 NVM burn 78

7 APPLICATION INFORMATION......................................................................................................79

7.1 Triple proximity reporting 79

7.2 Dual proximity reporting 80

7.2.1 SPM file (application two AOI, dual proximity reporting) 82

7.3 Example of Touch+Proximity Module 83

7.3.1 Overview 83

7.3.2 Operation 83

7.3.3 Performance 84

7.3.4 Schematics 84

7.3.5 Layout 85

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8 REFERENCES .............................................................................................................................86

9 PACKAGING INFORMATION ........................................................................................................87

9.1 Package Outline Drawing 87

9.2 Land Pattern 87

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SX8661

Low Power, Capacitive Button Touch and Proximity Controller

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1 GENERAL DESCRIPTION

1.1 Pin Diagram

SX8661

Top View

8 9 10 11 12 13 14

22232425262728

bottom ground pad

cap2

cap3

cap4

cap5

cap6

cap7

gnd

gpio5

gpio4

gpio3

gpio2

gpio1

gnd

gpio0

cap1

cap0

vana

resetb

gnd

gpio7

vdig

gpio6

vdd

scl

intb

sda

Figure 1 Pinout Diagram

1.2 Marking information

NC5B

yyww

xxxxx

R07

yyww = Date Code

xxxxx = Semtech lot number

R07 = Semtech Code

Figure 2 Marking Inform ation

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1.3 Pin Description

Number Name Type Description

1 CAP1 Analog Capacitive Sensor 1

2 CAP2 Analog Capacitive Sensor 2

3 CAP3 Analog Capacitive Sensor 3

4 CAP4 Analog Capacitive Sensor 4

5 CAP5 Analog Capacitive Sensor 5

6 CAP6 Analog Capacitive Sensor 6

7 CAP7 Analog Capacitive Sensor 7

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

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

10 VDD Power Main input power supply

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

12 SCL Digital Input I2C Clock, requires pull up resistor (in host or external)

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

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

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

16 GND Ground Ground

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

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

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

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

21 GND Ground Ground

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

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

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

25 GND Ground Ground

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

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

28 CAP0 Analog Capacitive Sensor 0

bottom plate GND Ground Exposed pad connect to ground

Table 1 P in descr ipt ion

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1.4 Simplified Block Diagram

The simplified block diagram of the SX8661 is illustrated in Figure 3.

vana

resetb

gnd

gpo7

vdig

gpo6

vdd

scl

intb

sda

Figure 3 Simplified block diagram of the SX8661

1.5 Acronyms

AOI Analog Output Interface

ASI Analog Sensor Interface

DCV Digital Compensation Value

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

SPO Special Purpose Output

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2 ELECTRICAL CHARACTERISTICS

2.1 Absolute Maximum Ratings

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

This is a stress rating only and functional operation of the device at these, or any other conditions beyond the “Recommended

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

reliability.

Parameter Symbol Min. Max. Unit

Supply Voltage VDD -0.5 3.9 V

Input voltage (non-supply pins) VIN -0.5 3.9 V

Input current (non-supply pins) IIN 10 mA

Operating Junction Temperature TJCT 125 °C

Reflow temperature TRE 260 °C

Storage temperature TSTOR -50 150 °C

ESD HBM (Human Body model)(i) ESDHBM 3 kV

Latchup(ii) I

LU ± 100 mA

Table 2 Absolute Maximum Ratings

(i) Tested to JEDEC standard JESD22-A114

(ii) Tested to JEDEC standard JESD78

2.2 Recommended Operating Conditions

Parameter Symbol Min. Max. Unit

Supply Voltage VDD 2.7 3.6 V

Supply Voltage Drop(iii, iv, v) VDDdrop 100 mV

Supply Voltage for NVM programming VDD 3.0 3.6 V

Ambient Temperature Range TA -40 85 °C

Table 3 Recom m ended Oper ating Conditions

(iii) Performance for 2.6V < VDD < 2.7V might be degraded.

(iv) Operation is not guaranteed below 2.6V. Should VDD briefly drop below this minimum value, then the SX8661 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 SX8661 and assures that parameters are re-written into the SPM (should these differ to the parameters held in NVM).

2.3 Thermal Characteristics

Parameter Symbol Min. Max. Unit

Thermal Resistance - Junction to Ambient (vi) θJA 25 °C/W

Table 4 Ther m al Char acteristics

(vi) Static airflow

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2.4 Electrical Specifications

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

Parameter Symbol Conditions Min. Typ. Max. Unit

Current consumption

Active mode, average IOP,active

30ms scan period,

8 sensors enabled,

common sensitivity 0

proximity sensing OFF

200 275 uA

Doze mode, average IOP,Doze

195ms scan period,

8 sensors enabled,

common sensitivity 0

proximity sensing OFF

70 100 uA

Sleep IOP,sleep I2C listening,

sensors disabled 8 17 uA

Active mode, average

(Quick Start application) IQS,active

30ms scan period,

8 sensors enabled,

sensitivity 2 for buttons

sensitivity 7 for proximity

proximity sensing ON

800 1100 uA

Doze mode, average

(Quick Start application) IQS,Doze

195ms scan period,

8 sensors enabled,

sensitivity 2 for buttons

sensitivity 7 for proximity

proximity sensing ON

160 220 uA

ResetB, SCL, SDA

Input logic high VIH 0.7*VDD VDD + 0.3 V

Input logic low VIL VSS applied to GND pins VSS - 0.3 0.8 V

Input leakage current LI CMOS input ±1 uA

Pull up resistor RPU when enabled 660 kΩ

Pull down resistor RPD when enabled 660 kΩ

GPIO set as Output, IntB, SDA

Output logic high VOH I

OH<4mA VDD-0.4 V

Output logic low VOL

IOL,GPIO<12mA

IOL,SDA,INTB<4mA

0.4 V

Start-up

Power up time tpor time between rising edge

VDD and rising INTB 275 ms

RESETB

ResetB pulse width tres 50 ns

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Parameter Symbol Conditions Min. Typ. Max. Unit

Recommended External components

capacitor between VDIG, GND Cvdig type 0402, tolerance +/-50% 100 nF

capacitor between VANA, GND Cvana type 0402, tolerance +/-50% 100 nF

capacitor between CP, CN Cint type 0402, COG, tolerance +/-5% 1 nF

capacitor between VDD, GND Cvdd type 0402, tolerance +/-50% 100 nF

Table 5 E lect rical Specifications

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Parameter Symbol Conditions Min. Typ. Max. Unit

I2C Timing Specifications (i)

SCL clock frequency fSCL 400 KHz

SCL low period tLOW 1.3 us

SCL high period tHIGH 0.6 us

Data setup time tSU;DAT 100 ns

Data hold time tHD;DAT 0 ns

Repeated start setup time tSU;STA 0.6 us

Start condition hold time tHD;STA 0.6 us

Stop condition setup time tSU;STO 0.6 us

Bus free time between stop and start tBUF 500 us

Input glitch suppression tSP 50 ns

Table 6 I 2C Tim ing Specification

Notes:

(i) All timing specifications, Figure 4 and Figure 5, refer to voltage levels (VIL, VIH, VOL) defined in Table 5.

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

Figure 4 I2C Start and Stop tim ing

Figure 5 I2C Data timing

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3 FUNCTIONAL DE S CRIPTION

3.1 Quickstart Application

The SX8661 is preconfigured (Quickstart Application) for an application requiring proximity and seven buttons,

with one Analog Output Interface and seven LED drivers using PWM fading. Table 7 summarises the default

configuration of the eight GPIOs available on the SX8661 Quickstart application.

GPIO Function Fading Mode Comments

0 LED Single Fading Mode Autolight, mapped on Btn1 (100% ON) and proximity (50% ON)

1 LED Single Fading Mode Autolight, mapped on Btn2 (100% ON) and proximity (50% ON)

2 LED Single Fading Mode Autolight, mapped on Btn3 (100% ON) and proximity (50% ON)

3 LED Single Fading Mode Autolight, mapped on Btn4 (100% ON) and proximity (50% ON)

4 LED Single Fading Mode Autolight, mapped on Btn5 (100% ON) and proximity (50% ON)

5 LED Single Fading Mode Autolight, mapped on Btn6 (100% ON) and proximity (50% ON)

6 LED Single Fading Mode Autolight, mapped on Btn7 (100% ON) and proximity (50% ON)

7 AOI-A Not applicable

Analog Output Interface A (VDD=3.3V)

Prox = Idle : 3.3V

Btn1: 0.6V

Btn2: 0.9V

Btn3: 1.2V

Btn4: 1.5V

Btn5: 1.8V

Btn6: 2.1V

Btn7: 2.4V

Table 7 Quickstart Application GPIO configuration

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

the SX8661 (even without host).

The default sensitivity is set to 0x02 for all button sensors (assumed button sensor area approximately 1 cm2

covered by 2mm thick acrylic overlay material) and 0x07 for the proximity sensor (typical 4 x 8 cm2).

Figure 6 Quickstart Application

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Figure 7 Quickstart LED and AOI reporting

Figure 7 shows the reporting on the LEDs and the AOI for the quickstart application.

The LEDs operate in triple reporting mode. In triple reporting mode the LEDs have three light intensities.

- OFF: out of proximity, no touch,

- Proximity: proximity detected,

- ON: button touched.

In case no fingers/hand is detected (out of proximity) all LEDs will be OFF and the AOI indicates the idle level.

In case a finger/hand is approaching proximity is detected and all LEDs will light up to 50% of the maximum

intensity. The AOI goes to the proximity voltage level (in the quickstart application the proximity level is chosen

identical to the idle level).

In case a button is touched the corresponding LED will go to 100% of intensity and the AOI voltage level indicates

the button that is touched.

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3.2 Introduction

3.2.1 General

The SX8661 is intended to be used in applications which require capacitive sensors covered by isolating overlay

material and which need to detect the proximity of a finger/hand though the air. A finger approaching the

capacitive sensors will change the charge that can be loaded on the sensors. The SX8661 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 SX8661 Analog Sensor Interface (ASI).

The ticks are further processed by the SX8661 and converted in a high level, easy to use information for the

user’s host.

The information between SX8661 and the user’s host is passed through the I2C interface with an additional

interrupt signal indicating that the SX8661 has new information. For buttons this information is simply touched or

released. The SX8661 can operate without the I2C and interrupt by using the analog output interface (GPIO7

and/or GPIO6) which voltage level indicates the button touched or GPO with the autolight function.

3.2.2 GPIOs

Feedback to the user is using General Purpose Input Output (GPIO) pins. The SX8661 offers up to 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 or proximity is detected and slowly fade-out when the button is released or finger goes out of

proximity. 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 step PWM. The SX8661 has eight individual PWM

generators, one for each GPIO pin.

The LED fading-in and fading-out mode is called the GPO (fading) mode.

The LED fading can be initiated automatically by the SX8661 by setting the SX8661 autolightening feature. A

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

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

setting the GPO pin to ‘high’ using one I2C command. The SX8661 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 the PWM mode

(GPP). 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 special purpose output (SPO) for the buzzer or analog output interface.

3.2.3 Analog Output Interface A and B (SPO mode)

The Analog Output Interface (AOI) is a PWM output signal between ground and VDD. The duty cycle of the AOI

output will change depending on which button is touched. A host controller can then measure the mean voltage

delivered on the AOI output and determine which button is touched at any given time.

The AOI feature allows the SX8661 device to replace directly legacy mechanical button controllers in a quick and

effortless manner. The SX8661 supports up to two Analog Output Interfaces, AOI-A and AOI-B (on GPIO7 and

GPIO6 respectively). The SX8661 allows buttons to be mapped on either AOI-A or AOI-B. The button mapping as

well as the mean voltage level that each button produces on a AOI output can be configured by the user through a

set of parameters described in later chapters (see 5.6).

3.2.4 Buzzer (SPO mode)

The SX8661 can drive a buzzer (on GPIO5) to provide audible feedback on button touches. The buzzer duration

is set to approximately 30ms per default (see 5.7).

3.2.5 Parameters

The SX8661 has many low level built-in, fixed algorithms and procedures. To allow a lot of freedom for the user

and adapt the SX8661 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

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are buttons, which GPIO is used for outputs, for the Analog Output Interfaces, the Buzzer 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.

3.2.6 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

SX8661 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 SX8661. The programming needs to be done once (over the I2C). The SX8661 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.

3.3 Scan Period

The basic operation Scan period of the SX8661 sensing interface can be split into three periods over time.

In the first period (Sensing) the SX8661 is sensing all enabled CAP inputs, from CAP0 towards CAP7.

In the second period (Processing) the SX8661 processes the sensor data, verifies and updates the GPIO and the

I2C.

In the third period (Timer) the SX8661 is set in a low power mode and waits until a new cycle starts.

Figure 8 shows the different SX8661 periods over time.

Figure 8 Scan Period

The scan period determines the minimum reaction time of the SX8661. 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 SX8661

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

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

longer reaction times.

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

period.

3.4 Operation modes

The SX8661 has 3 operation modes. The main difference is found in the reaction time (corresponding to the scan

period) and power consumption.

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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 SX8661 OFF, except for the I2C peripheral, minimizing operating current while maintaining

the power supplies. In Sleep mode the SX8661 does not do any sensor scanning. The Sleep mode will be exited

by any I2C access.

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 SX8661 is not used for a specific time it will 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.

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

The host can decide to force the operating mode by issuing commands over the I2C (using register GpioOpMode)

and take fully control of the SX8661. The diagram in Figure 9 shows the available operation modes and the

possible transitions.

Figure 9 Operation modes

3.5 Sensors on the PCB

The capacitive sensors are relatively simple copper areas on the PCB connected to the eight SX8661 capacitive

sensor input pins (CAP0…CAP7).The sensors are covered by isolating overlay material (typically 1mm...3mm).

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

the overlay material. The area of a proximity sensor is usually a factor larger as the smaller touch sensors.

The capacitive sensors can be setup as ON/OFF buttons for touch sensing and CAP0 offers additionally proximity

sensing (see example Figure 10) for control applications.

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Figure 10 PCB top layer of three touch buttons sensors surrounded by a proximity sensor

Please refer to the layout guidelines application note [1], for more details.

3.6 Button Information

The touch 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 tick from the ASI goes below the threshold minus a hysteresis. The hysteresis around

the threshold avoids rapid touch and release signalling during transients.

Buttons can also be used to do proximity sensing. The principle of proximity sensing operation is exactly the same

as for touch buttons except that proximity sensing is done several centimeters above the overlay through the air.

ON state means that finger/hand is detected by the sensor and OFF state means the finger/hand is far from the

sensor and not detected.

3.7 Buzzer

The SX8661 has the ability to drive a buzzer (on GPIO5) to provide an audible indication that a button has been

touched. The buzzer is driven by a square signal for approximately 30ms (default). During the first phase (15ms)

the signal’s frequency is default 4KHz while in the second phase (15ms) the signal’s frequency default is 8KHz.

The buzzer is activated only once during any button touch and is not repeated for long touches. The user can

choose to enable or disable the buzzer by configuration and define the idle level, frequencies and phase durations

(see 5.7).

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Figure 12 Buzzer behavior

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3.8 Analog Output Interface

The Analog Output Interface outputs a PWM signal with a varying duty cycle depending on which button is

touched. By filtering (with a simple RC filter) the PWM signal results in a DC voltage, different for each button

touch. The host controller measures the DC voltage level and determines which buttons has been touched.

In the case of single button touches, each button produces its own voltage level as configured by the user (see

5.6 and Table 8).

Figure 13 show how the AOI will behave when the user touches and releases different buttons.

The AOI will switch between the AOI idle level and the level for each button.

Figure 13 AOI behavior

The PWM blocks used in AOI modes are 8-bits based and clocked at 2MHz typically.

The PWM period can be set to 256 (default) or 64. The 256 period offers a better granularity at a lower frequency,

while the 64 period is faster and with fewer steps.

Figure 14 shows the PWM definition of the AOI.

Figure 14 PWM definit ion, ( a ) small pulse width, (b) large pulse width

Table 8 describes the AOI level index versus the PWM pulse width. The user can select 256 steps (index) in case

the period is set to 255.

In case the period is set to 64 then the index from 0 to 63 applies.

Index Width Index Width Index Width Index Width Index Width Index Width Index Width Index Width

0 0 32 33 64 65 96 97 128 129 160 161 192 193 224 225

1 2 33 34 65 66 97 98 129 130 161 162 193 194 225 226

2 3 34 35 66 67 98 99 130 131 162 163 194 195 226 227

3 4 35 36 67 68 99 100 131 132 163 164 195 196 227 228

4 5 36 37 68 69 100 101 132 133 164 165 196 197 228 229

5 6 37 38 69 70 101 102 133 134 165 166 197 198 229 230

6 7 38 39 70 71 102 103 134 135 166 167 198 199 230 231

7 8 39 40 71 72 103 104 135 136 167 168 199 200 231 232

8 9 40 41 72 73 104 105 136 137 168 169 200 201 232 233

9 10 41 42 73 74 105 106 137 138 169 170 201 202 233 234

10 11 42 43 74 75 106 107 138 139 170 171 202 203 234 235

11 12 43 44 75 76 107 108 139 140 171 172 203 204 235 236

12 13 44 45 76 77 108 109 140 141 172 173 204 205 236 237

13 14 45 46 77 78 109 110 141 142 173 174 205 206 237 238

14 15 46 47 78 79 110 111 142 143 174 175 206 207 238 239

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Index Width Index Width Index Width Index Width Index Width Index Width Index Width Index Width

15 16 47 48 79 80 111 112 143 144 175 176 207 208 239 240

16 17 48 49 80 81 112 113 144 145 176 177 208 209 240 241

17 18 49 50 81 82 113 114 145 146 177 178 209 210 241 242

18 19 50 51 82 83 114 115 146 147 178 179 210 211 242 243

19 20 51 52 83 84 115 116 147 148 179 180 211 212 243 244

20 21 52 53 84 85 116 117 148 149 180 181 212 213 244 245

21 22 53 54 85 86 117 118 149 150 181 182 213 214 245 246

22 23 54 55 86 87 118 119 150 151 182 183 214 215 246 247

23 24 55 56 87 88 119 120 151 152 183 184 215 216 247 248

24 25 56 57 88 89 120 121 152 153 184 185 216 217 248 249

25 26 57 58 89 90 121 122 153 154 185 186 217 218 249 250

26 27 58 59 90 91 122 123 154 155 186 187 218 219 250 251

27 28 59 60 91 92 123 124 155 156 187 188 219 220 251 252

28 29 60 61 92 93 124 125 156 157 188 189 220 221 252 253

29 30 61 62 93 94 125 126 157 158 189 190 221 222 253 254

30 31 62 63 94 95 126 127 158 159 190 191 222 223 254 255

31 32 63 64 95 96 127 128 159 160 191 192 223 224 255 256

Table 8 AOI Level index vs. PWM pulse width (normal polarity)

The AOI reports always one button. The AOI can be split over two GPIO pins (AOI-A, AOI-B). The AOI-A interface

is connected to pin GPIO7 and the AOI-B is connected to pin GPIO6. The user can map any button to either AOI-

A or AOI-B or both.

In case buttons are split to both AOI pins, multiple button touches are still resulting in one AOI reporting.

In most applications only one AOI pin will be selected. The two AOI pins allow the user a more coarse detection

circuitry at the host. Assuming a 3.3V supply and 8 buttons on one single AOI then the AOI levels could be

separated with around 0.3…0.4V. In case of using the two AOI pins, 4 buttons could be mapped on AOI-A

separated with around 0.8V (similar for 4 buttons on AOI-B) which step is about the double in case of a single

AOI.

In case of a single touch the reported button is straight forward (as in Figure 13).

If more than one button is touched the reported depends on the selected button reporting mode parameter ( 5.5).

Three reporting modes exist for the SX8661 (All, Single and Strongest).

The All reporting mode is applicable only for the I2C reporting (AOI is not available). In All-mode all buttons that

are touched are reported in the I2C buttons status bits.

In the Single-mode a single touched button will be reported on the AOI and the I2C. All touches that occur

afterwards will not be reported as long as the first touch sustains. Only when the first reported button is released

will the SX860 report another touch.

Figure 15 shows the Single-mode reporting in case of 2 touches occurring over time.

Figure 15 Single-mode reporting with 2 touches

At time t1 button0 is touched and reported on the AOI. At time t2 button1 is touched as well but not reported. At

time t3 the button0 is released and button1 will be reported immediately (or after one scan period at idle level).

At time t4 both buttons are released and the AOI reports the idle level.

The button with the lowest Cap pin index will be reported in case of a simultaneous touch (that means touches

occurring within the same scan period).

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In the Strongest-mode the strongest touched button will be reported on the AOI and the I2C. All touches that

occur afterwards representing a weaker touch will not be reported. Only a touch which is stronger will be reported

by the SX860.

Figure 16 shows the Strongest-mode reporting in case of 2 touches (with bt1 the strongest touch).

Figure 16 Strongest-mode reporting with 2 touches

At time t1 button0 is touched and reported on the AOI. At time t2 button1 is touched as well. As bt1 is the

strongest touch it will be reported on the AOI immediately (or after one scan period at idle level). At time t3 the

button0 is released while the AOI continues to report button1. At time t4 both buttons are released and the AOI

reports the idle level.

In some special cases (when the buzzer is suspected to load heavily the power supply) the user may choose the

AOI to go to 0V, to VDD or to the AOI idle level for the duration the buzzer is active.

Figure 17 AOI behavior with 0V buzzer state

In Figure 17 the AOI will go to 0V each time the buzzer is active. The AOI returns then to either the idle mode for

one scan period or goes immediately to the PWM button level.

In case the SX8661 is set to sleep mode the AOIs will go to 0V.

3.9 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 18).

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Figure 18 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 SX8661 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 touch/proximity detection

will not be possible. In case the sensitivity is set too large, some power will be wasted and false touch/proximity

information may be output (i.e. for touch buttons => finger not touching yet, for proximity sensors => finger/hand

not close enough).

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

until all (enabled) sensors pins have been treated.

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

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

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

The ASI will shut down and wait until new sensing period will start.

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3.10 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 SX8661 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 SX8661 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 SX8661 is shut down the compensation values will be lost. At a next power-up the procedure starts all over

again. This assures that the SX8661 will operate under any condition. Powering up at e.g. different temperatures

will not change the performance of the SX8661 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 SX8661 will initiate a compensation procedure

and find a new set of DCVs.

Compensation procedures can as well be initiated by the SX8661 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. This is e.g. required after the

host changed the sensitivity of sensors.

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3.11 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 19).

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 19 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.

3.12 Configuration

Figure 20 shows the building blocks used for configuring the SX8661.

Figure 20 Configuration

The default configuration parameters of the SX8661 are stored in the Quick Start Memory (QSM). This

configuration data is setup to a very common application for the SX8661 with 8 buttons. Without any programming

or host interaction the SX8661 will start up in the Quick Start Application.

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

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In case the application needs different settings than the QSM settings then the SX8661 can be setup and/or

programmed over the I2C interface.

The configuration parameters of the SX8661 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 SX8661 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 SX8661 copies the configuration parameter source into the Shadow Parameter Memory (SPM). The

SX8661 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 following power up

or at the end of the reset event.

The host will interface with the SX8661 through the I2C bus and the analog output interface.

The I2C of the SX8661 consists of 16 registers. Some of these I2C registers are used to read the status and

information of the buttons. Other I2C registers allow the host to take control of the SX8661. The host can e.g.

decide to change the operation mode from active mode to Doze mode or go into sleep (according Figure 9).

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 21 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 small deviations from the QSM or NVM

content.

Figure 21 Host SPM mode

The content of the SPM remains valid as long as the SX8661 is powered. After a power down the host needs to

re-write the SPM at the next power-up.

Figure 22 shows the Host NVM mode. In this mode the host will be able to write the NVM.

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Figure 22 Host NVM mode

The writing of the host towards the NVM is not done directly but done in 2 steps (Figure 22).

In the first step the host writes to the SPM (as in Figure 21). In the second step the host signals the SX8661 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).

3.13 Power Management

The SX8661 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 SX8661 internal circuitry and must not be loaded

externally.

3.14 Clock Circuitry

The SX8661 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.

3.15 I2C interface

The I2C interface allows the communication between the host and the SX8661.

The I2C slave implemented on the SX8661 is compliant with the standard (100kb/s) and fast mode (400kb/s)

The default SX8661 I2C address equals 0b010 1011.

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

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3.16 Interrupt

3.16.1 Power up

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

autonomously. The SX8661 is then ready for operation. The AOI levels are updated at the latest one scan period

after the rising edge of INTB.

Figure 23 Power Up vs. INTB

During the power on period the SX8661 stabilizes the internal regulators, RC clocks and the firmware initializes all

registers.

During the power up the SX8661 is not accessible and I2C communications are forbidden. The GPIOs set as

inputs with a pull up resistor.

As soon as the INTB rises the SX8661 will be ready for I2C communication. The GPIOs are then configured

according the parameters in the SPM.

The value of INTB before power up depends on the INTB pull up resistor supply voltage.

3.16.2 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 register CapStatLsb show the detailed status of

the Buttons,

• when actually entering Active or Doze mode via a host request (may be delayed by 1 scan period). I2C

• 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).

3.16.3 Clearing

The clearing of the INTB is done as soon as the host performs a read to any of the SX8661 I2C registers.

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3.16.4 Example

A typical example of the assertion and clearing of the INTB and the I2C communication is shown in Figure 24.

Figure 24 Interrupt and I2C

When a button is touched the SX8661 will assert the interrupt (1). The host will read the SX8661 status

information over the I2C (2) and this clears the interrupt.

If the finger releases the button the interrupt will be asserted (3), the host reads the status (4) which clears the

interrupt.

In case the host will not react to an interrupt then this will result in a missing touch.

3.17 Reset

The reset can be performed by 3 sources:

- power up,

- RESETB pin,

- software reset.

3.17.1 Power up

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

autonomously. The SX8661 is then ready for operation.

Figure 25 Power Up vs. INTB

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During the power on period the SX8661 stabilizes the internal regulators, RC clocks and the firmware initializes all

registers.

During the power up the SX8661 is not accessible and I2C communications are forbidden.

As soon as the INTB rises the SX8661 will be ready for I2C communication.

3.17.2 RESETB

When RESETB is driven low the SX8661 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 26 Har dware Reset

3.17.3 Software Reset

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

0xB1.

Figure 27 Software Reset

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3.18 General Purpose Input and Outputs

The SX8661 offers eight General Purpose Input and Outputs (GPIO) pins which can be configured in any of these

modes:

- GPP (General Purpose PWM)

- GPO (General Purpose Output)

- SPO (Special Purpose Output)

The input state of the GPIO is only used during the initial phase of the power up period.

Each of these GPIO 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 28 polarity = 1 (a), polarity = 0 (b)

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 0.5us typ.

Figure 29 PWM definit ion, ( a ) small pulse width, (b) large pulse width

3.18.1 GPP mode

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.

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Figure 30 LED contro l in GPP mode

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

parameters sections for more details.

GPP

GpioMode X

GpioOutPwrUp X1

GpioPolarity X

GpioIntensityOn X1

GpioIntensityOff X1

SPM

GpioFunction X

GppPinId X

I2C GppIntensity X1

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

corresponding bits value.

Table 9 SPM/ I 2C Parameters Applicable in GPP Mode

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3.18.2 GPO Dual Reporting

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. This is the dual reporting mode.

The SX8661 offers additionally a triple reporting mode which allows the reporting of proximity by a medium strong

LED intensity (section 3.18.5).

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 31 LED Control in G PO m ode, Autolight OFF

Figure 32 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 33 GPO ON transition (L ED f ade in), normal polarity, (a) linear , (b) logarithm ic

Figure 34 GPO ON transition (L ED f ade in), inverted polarit y, (a) linear, (b) logarithmic

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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 35 and Figure 36).

Figure 35 GPO OFF transition ( L ED fade out), normal polarity, (a) linear, (b) logarithmic

Figure 36 GPO OFF transition ( LED fade out), invert ed polarit y, (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 (i.e. OFF) and programming intensity OFF/ON to 0x00 and 0xFF.

3.18.3 GPO Fading

The SX8661 supports two different fading modes, namely Single and Continuous. These fading modes can be

configured for each GPIO individually. Please see 5.9 “GPIO Parameters” for more information on how to

configure this feature.

i) Single Fading Mode:

The GPO pin fades in when the associated button is touched and it fades out when it is released. This is shown in

Figure 37

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fading-in

OFF intensity

ON intensity

delay_off fading-out

OFF intensity

OFF

Figure 37 Single Fading Mode

ii) Continuous Fading Mode:

The GPO pin fades in and fades out continuously when the associated button is touched. The fading in and out

stops when the button is released. This is shown in Figure 38.

fading-in

OFF intensity

ON intensity

fading-out

OFF intensity

OFF

Figure 38 Continuous Fading Mode

3.18.4 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

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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 I nt ensity index vs. PWM pulse width (inverted polarity)

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

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

3.18.5 GPO Triple Reporting

The button information touch and release can be reported on the LEDs in dual mode (ON and OFF).

The proximity information can be shown using the dual mode by attributing a dedicated LED to the proximity

sensor. The LED will show then proximity detected or no proximity detected. The fading principles are equal to the

fading of sensors defined as buttons as described in the previous sections.

In triple mode proximity is reported on all LEDs by an intermediate LED intensity.

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Figure 39 LEDs in triple reporting mode proximity

Figure 39 shows an example of proximity detection and the reporting on LEDs. As soon as proximity is detected

all LEDs (2 LEDs are shown for simplicity) will fade in and stop at the proximity intensity level. In case proximity is

not detected anymore then the LEDs remain at the proximity intensity for a configurable time and then the fading

out will start.

Figure 40 LEDs in triple reporting mode proximity and touch

Figure 40 shows an example of proximity detection followed by a rapid touch on the sensor sd1.

The LEDs d1 and d2 will fade in as soon as proximity is detected (using the Inc_Prox parameter).

As soon as the finger touches the sensor sd1 the fading in of d1 will go to the ON intensity (using the touch

increment parameter).

The LED d2 remains at the proximity intensity level as sensors sd2 is not touched.

If the finger is removed rapidly the fading out of d1 will first use the touch decrement parameter to the proximity

intensity level. If the finger leaves the proximity region d1 and 2 will fade out simultaneously using the proximity

delay and decrement parameters.

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4 PIN DESCRIPTIONS

4.1 Introduction

This chapter describes briefly the pins of the SX8661, the way the pins are protected, if the pins are analog,

digital, require pull up or pull down resistors and show control signals if these are available.

4.2 ASI pins

CAP0, CAP1,...,CAP7

The capacitance sensor pins (CAP0, CAP1,...,CAP7) are connected directly to the ASI circuitry which converts

the sensed capacitance into digital values.

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

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

some ohms, connection vias are allowed).

The capacitance sensor pins are protected to VANA and GROUND.

Figure 41 shows the simplified diagram of the CAP0, CAP1,...CAP7 pins.

SX8661

sensor ASI CAPx CAP_INx

VANA

Note : x = 0, 1,2,…7

Figure 41 Simplif ied diagr am of CAP0, CAP1,...,CAP7

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 SX8661.

The CN and CP are protected to VANA and GROUND.

Figure 42 shows the simplified diagram of the CN and CP pins.

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Figure 42 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 43 shows a simplified diagram of the INTB pin.

Figure 43 Simplified diagram of INTB

SX8661

ASI

VANA

VDD

R_INT

INTB

SX8661

INT

to host

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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 44 shows the simplified diagram of the SCL pin.

Figure 44 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 45 shows the simplified diagram of the SDA pin.

Figure 45 Simplified diagram of SDA

VDD

SCL

SX8661

from host

SCL_IN

VDD

SDA

SX8661

SDA_OUT

from

to host

SDA_IN

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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 46 shows the simplified diagram of the RESETB pin controlled by the host.

Figure 46 Simplified diagr am of RESETB controlled by host

Figure 47 shows the RESETB without host control.

Figure 47 Simplified diagr am of RESETB wit hout host control

VDD

RESETB

SX8661

from host

RESETB_IN

VDD

RESETB

SX8661

RESETB_IN

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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 SX8661.

VDD has protection to GROUND.

Figure 48 shows a simplified diagram of the VDD pin.

Figure 48 Simplified diagram of VDD

GND

The SX8661 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 49 shows a simplified diagram of the GND pin.

Figure 49 Simplified diagram of GND

VDD

SX8661

VDD

SX8661

GND

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VANA, VDIG

The SX8661 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 50 shows a simplified diagram of the VANA and VDIG pin.

Figure 50 Simplified diagram of VANA and VDIG

4.5 General purpose IO pi ns

The SX8661 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 GPO, SPO or GPP.

Figure 51 shows a simplified diagram of the GPIO pins.

Figure 51 Simplified diagram of GPIO pins

VDD

SX8661

GND

VDIG

VDD

GND

VANA

VDIG

Cvdig

Cvana

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5 DETAILED CONFIGURATION DESCRIPTIONS

5.1 Introduction

The SX8661 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 SX8661.

The SPM is split by functionality into 5 configuration sections:

• General section: operating modes,

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

• Proximity: defining parameters related to proximity sensing

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

• AOI: defining parameters for the AOI

• Buzzer: defining parameters for the AOI

• Mapping: related to mapping of button information towards 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 ProxReporting 0x7F

0x01 Reserved 0xxx 0x21

ProxIntensity 0x64

0x02 Reserved 0x41 0x22 BtnCfg 0x70

0x03 Reserved 0xxx 0x23 BtnAvgThresh 0x50

0x04 I2CAddress 0x2B 0x24 BtnCompNegThresh 0xA0

0x05 ActiveScanPeriod 0x02 0x25 BtnCompNegCntMax 0x01

0x06 DozeScanPeriod 0x0D 0x26 BtnHysteresis 0x0A

0x07 PassiveTimer 0x00 0x27 BtnStuckAtTimeout 0x00

0x08

General

Reserved 0x00 0x28 BtnStrongestHysteresis 0x80

0x09 CapModeMisc 0x04 0x29 BtnLongPressTimer 0x00

0x0A Reserved 0x00 0x2A

Button

Reserved 0xFF

0x0B CapMode7_4 0x55 0x2B AoiCfg 0x01

0x0C CapMode3_0 0x57 0x2C AoiBtnMapMsb 0x55

0x0D CapSensitivity0_1 0x72 0x2D AoiBtnMapLsb 0x55

0x0E CapSensitivity2_3 0x22 0x2E AoiLevelBtn0 0xFF

0x0F CapSensitivity4_5 0x22 0x2F AoiLevelBtn1 0x2E

0x10 CapSensitivity6_7 0x22 0x30 AoiLevelBtn2 0x45

0x11 Reserved 0x00 0x31 AoiLevelBtn3 0x5D

0x12 Reserved 0x00 0x32 AoiLevelBtn4 0x74

0x13 CapThresh0 0xA0 0x33 AoiLevelBtn5 0x8B

0x14 CapThresh1 0xA0 0x34 AoiLevelBtn6 0xA3

0x15 CapThresh2 0xA0 0x35 AoiLevelBtn7 0xBA

0x16 CapThresh3 0xA0 0x36

Analog Output Interface (AOI)

AoiLevelIdle 0xFF

0x17 CapThresh4 0xA0 0x37 BuzzerCfg 0xA4

0x18 CapThresh5 0xA0 0x38 BuzzerFreqPhase1 0x40

0x19 CapThresh6 0xA0 0x39 BuzzerFreqPhase2 0x20

0x1A CapThresh7 0xA0 0x3A

Buzzer

Reserved 0x00

0x1B

Capacitive Sensors

CapPerComp 0x00 0x3B MapAutoLight0 0x07

0x1C ProxIncDecTime 0x14 0x3C MapAutoLight1 0x65

0x1D ProxCfg 0xB0 0x3D MapAutoLight2 0x43

0x1E ProxDebounce 0x00 0x3E MapAutoLight3 0x21

0x1F

Proximity

ProxHysteresis 0x0A 0x3F

Mapping

MapAutoLightGrp0Msb 0x00

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 MapAutoLightGrp0Lsb 0x00 0x60 GpioDecTime7_6 0x44

0x41 MapAutoLightGrp1Msb 0x00 0x61 GpioDecTime5_4 0x44

0x42

Mapping

MapAutoLightGrp1Lsb 0x00 0x62 GpioDecTime3_2 0x44

0x43 GpioMode7_4 0xC0 0x63 GpioDecTime1_0

0x44

0x44 GpioMode3_0 0x00 0x64 GpioOffDelay7_6 0x00

0x45 GpioIntensityOn0 0xFF 0x65 GpioOffDelay5_4 0x00

0x46 GpioIntensityOn1 0xFF 0x66 GpioOffDelay3_2 0x00

0x47 GpioIntensityOn2 0xFF 0x67 GpioOffDelay1_0 0x00

0x48 GpioIntensityOn3 0xFF 0x68 GpioPullUpDown7_4 0x00

0x49 GpioIntensityOn4 0xFF 0x69 GpioPullUpDown3_0 0x00

0x4A GpioIntensityOn5 0xFF 0x6A Reserved 0x00

0x4B GpioIntensityOn6 0xFF 0x6B Reserved 0x00

0x4C GpioIntensityOn7 0xFF 0x6C Reserved 0x00

0x4D GpioIntensityOff0 0x00 0x6D GpioFadingMode7_4 0x00

0x4E GpioIntensityOff1 0x00 0x6E

Gpio

GpioFadingMode3_0 0x00

0x4F GpioIntensityOff2 0x00 0x6F Reserved 0x50

0x50 GpioIntensityOff3 0x00 0x70 CapProxEnable 0x74

0x51 GpioIntensityOff4 0x00 0x71

Reserved 0x10

0x52 GpioIntensityOff5 0x00 0x72 Reserved 0x45

0x53 GpioIntensityOff6 0x00 0x73 Reserved 0x03

0x54 GpioIntensityOff7 0x00 0x74 Reserved 0xFF

0x55 Reserved 0xFF 0x75 Reserved 0xFF

0x56 GpioOutPwrUp 0x00 0x76 Reserved 0xFF

0x57 GpioAutoLight 0xFF 0x77 Reserved 0xD5

0x58 GpoPolarity 0x80 0x78 Reserved 0x55

0x59 GpioFunction 0x80 0x79 Reserved 0x55

0x5A GpioIncFactor 0x00 0x7A Reserved 0x7F

0x5B GpioDecFactor 0x00 0x7B Reserved 0x23

0x5C GpioIncTime7_6 0x11 0x7C Reserved 0x22

0x5D GpioIncTime5_4 0x11 0x7D Reserved 0x41

0x5E GpioIncTime3_2 0x11 0x7E Reserved 0xFF

0x5F

Gpio

GpioIncTime1_0 0x11 0x7F

SpmCrc1 0x3F

Table 13 SPM address map: 0x40…0x7F

Note1

• 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 (0x00). 0x04 I2CAddress

6:0 Defines the I2C address.

The I2C address will be active after a reset.

Default: 0x2B

0x05 ActiveScanPeriod 7:0 Defines Active Mode Scan Period (Figure 8).

0x00: Reserved

0x01: 15ms

0x02: 30ms

…

0xFF: 255 x 15ms

Default: 0x02

0x06 DozeScanPeriod 7:0 Defines Doze Mode Scan Period (Figure 8).

0x00: Reserved

0x01: 15ms

…

0x0D: 195ms

…

0xFF: 255 x 15ms

Default: 0x0D

0x07 PassiveTimer 7:0 Defines Passive Timer on Button Information (Figure 9).

0x00: OFF

0x01: 1 second

…

0xFF: 255 seconds

Default: 0x00

0x08 Reserved 7:0 Reserved (0x00)

Table 14 G ener al Par a m eter s

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5.3 Capacitive Sensors Pa rameters

Capacitive Sensors Parameters

Address Name Bits Description

7:3 Reserved (0x00) 0x09 CapModeMisc

2:0 IndividualSensitivity Defines common sensitivity for all sensors or individual sensor

sensitivity.

000: Common sensitivity settings (CapSensitivity0_1[7:4])

100: Individual sensitivity settings (CapSensitivityx_x) (default)

Else : Reserved

0x0A Reserved 7:0 Reserved (0x00)

7:6 CAP7 Mode Default Button

5:4 CAP6 Mode Default Button

3:2 CAP5 Mode Default Button

0x0B CapMode7_4

1:0 CAP4 Mode Default Button

7:6 CAP3 Mode Default Button

5:4 CAP2 Mode Default Button

3:2 CAP1 Mode Default Button

0x0C CapMode3_0

1:0 CAP0 Mode

Defines the mode of the CAP pin.

00: Disabled

01: Button

10: Reserved

11: Proximity (CAP0),

Reserved (CAP6,..CAP1)

Default: 0x5557

Default Proximity

7:4 CAP0 Sensitivity - Common Sensitivity 0x0D CapSensitivity0_1

3:0 CAP1 Sensitivity

7:4 CAP2 Sensitivity 0x0E CapSensitivity2_3

3:0 CAP3 Sensitivity

7:4 CAP4 Sensitivity 0x0F CapSensitivity4_5

3:0 CAP5 Sensitivity

7:4 CAP6 Sensitivity 0x10 CapSensitivity6_7

3:0 CAP7 Sensitivity

Defines the sensitivity.

0x0: Minimum

0x1: 1

…

0x7: Maximum

0x8..0xF: Reserved

Default CapSensitivity0_1: 0x72

Default CapSensitivity2_3: 0x22

Default CapSensitivity4_5: 0x22

Default CapSensitivity6_7: 0x22

0x11 Reserved 7:0 Reserved (0x00)

0x12 Reserved 7:0 Reserved (0x00)

0x13 CapThresh0 7:0 CAP0 Touch Threshold

0x14 CapThresh1 7:0 CAP1 Touch Threshold

0x15 CapThresh2 7:0 CAP2 Touch Threshold

0x16 CapThresh3 7:0 CAP3 Touch Threshold

0x17 CapThresh4 7:0 CAP4 Touch Threshold

0x18 CapThresh5 7:0 CAP5 Touch Threshold

0x19 CapThresh6 7:0 CAP6 Touch Threshold

0x1A CapThresh7 7:0 CAP7 Touch Threshold

Defines the Touch Threshold ticks.

0x00: 0,

0x01: 4,

…

0xA0: 640 (default),

…

0xFF: 1020

7:4 Reserved (0x00) 0x1B CapPerComp

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

0x0: OFF (default)

0x1: 1 second

0x2: 2 seconds

…

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Capacitive Sensors Parameters

Address Name Bits Description

0x7: 7 seconds

0x8: 16 seconds

0x9: 18 seconds

…

0xE: 28 seconds

0xF: 60 seconds

0x70 CapProxEnable 7:0 Enables proximity sensing.

0x46: OFF

0x74: ON (default)

Table 15 Capacitive Sensors Parameters

CapModeMisc:

By default the ASI is using an individual sensitivity for each CAP pin (with proximity sensor set to maximum

sensitivity while touch sensors are set to a lower one). The individual sensitivity mode results in longer sensing

periods than required in common sensitivity mode.

The ASI can use common sensitivity for all capacitive sensors in the 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.

CapMode7_4, CapMode3_0:

The CAP7 to CAP0 pins can be set as a button or disabled depending on the application.

CAP0 can be used for proximity sensing (additionally set register CapProxEnable).

minimum maximum

Buttons zero seven

Table 16 Number of buttons (with CAP0 = proximity)

minimum maximum

Buttons one eight

Table 17 Number of buttons (with CAP0 = button or disabled)

Buttons and disabled CAP pins can be attributed freely (examples in Figure 52).

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Figure 52 Button examples

CapSensitivity0_1, CapSensitivity2_3, CapSensitivity4_5, CapSensitivity6_7, CapProxEnable:

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 or proximity sensing.

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

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

above the touch sensors.

The 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[2:0].

The maximum number of ticks that can be obtained depends on the selected sensitivity and if proximity sensing is

enabled. This is illustrated in Table 18.

Sensitivity Approximate

Maximum Tick Level

(CapProxEnable = OFF)

Approximate

Maximum Tick Level

(CapPro x Enab l e = ON)

0 1000 4000

1 2000 8000

2 3000 12000

3 4000 16000

4 5000 20000

5 6000 24000

6 7000 28000

7 8000 32000

Table 18 ASI Maximum Tick Levels

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

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

The threshold levels are used by the SX8661 for making touch and release decisions.

The details are explained in the sections for buttons.

CapPerComp:

The SX8661 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 buttons are

released.

CapProxEnable:

The SX8661 is intended to be used with proximity. This register is set by default to ON (0x74). In case

proximity is not required then this register should be set to OFF (0x46) and CAP0 Mode should be set to button

or disabled.

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5.4 Proximity Parameters

Proxim it y Param et e rs

Address Name Bits Description

7:4 Defines the time between each increment.

0x0: instantaneous

0x1: 0.5ms (default)

0x2: 1ms

…

0xF: 7.5ms

0x1C ProxIncDecTime

3:0 Defines the time between each decrement.

0x0: instantaneous

0x1: 0.5ms

0x2: 1ms

…

0x4: 2ms (default)

…

0xF: 7.5ms

7:4 Defines the delay between release and start of fading out.

0x0: instantaneous

0x1: 200 ms

0x2: 400 ms

0x3: 600ms

…

0xA: 2s

0xB: 4s (default)

…

0xF: 12s

3:2 Reserved (0x00)

1 Defines the fading increment factor.

0: intensity index incremented every increment time (default)

1: intensity index incremented every 16 increment times

0x1D ProxCfg

0 Defines the fading decrement factor.

0: intensity index decremented every decrement time (default)

1: intensity index decremented every 16 decrement times

7:4 Reserved (0x00)

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

00 : no debounce, use incoming sample (default)

01 : 2 samples debounce

10 : 3 samples debounce

11 : 4 samples debounce

0x1E ProxDebounce

1:0 Defines the number of samples at the scan period for determining proximity detection.

00 : no debounce, use incoming sample (default)

01 : 2 samples debounce

10 : 3 samples debounce

11 : 4 samples debounce

0x1F ProxHysteresis 7:0 Defines the proximity hysteresis corresponding to a percentage of the CAP0 threshold

(defined in Table 15).

0x00: 0%

0x01: 1%

…

0x0A: 10% (default)

…

0x64: 100%

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Proxim it y Param et e rs

Address Name Bits Description

0x20 ProxReporting 7:0 Defines triple or dual mode reporting of proximity on the GPIOs.

0x00: dual mode

0x7F: triple mode (default)

0x21 ProxIntensity 7:0 Defines the proximity ON intensity index.

0x00: 0

0x01: 1

…

0x64: 100 (default)

…

0xFF: 255

Table 19 Proximity Paramet ers

ProxDebounce

Defines the number of samples for determining proximity detection or out of proximity detection.

This parameter allows to set the debouncer of the proximity differently from the buttons debouncer.

ProxHysteresis

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

CapThreshold0 + CapThreshold0 * hysteresis.

Out of proximity is detected if the ticks are getting smaller as the value defined by:

CapThreshold0 – CapThreshold0 * hysteresis.

ProxReporting

Defines the reporting mode of proximity (either dual or triple) on the GPIOs.

ProxIntensity

Defines the proximity intensity index (applicable in triple reporting mode).

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5.5 Button Parameters

Button Parameters

Address Name Bits Description

7:6 Defines the buttons and proximity events reporting method on I2C, AOI, GPO,

Buzzer (see Table 21 for details).

00: All

01: Single (default)

10: Strongest

11: Reserved

5:4 Defines the buttons interrupt (for all buttons and proximity).

00 : Interrupts masked

01 : Triggered on Touch

10 : Triggered on Release

11 : Triggered on Touch and Release (default)

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

button.

00 : no debounce, use incoming sample (default)

01 : 2 samples debounce

10 : 3 samples debounce

11 : 4 samples debounce

0x22 BtnCfg

2:0 Defines the number of samples at the scan period for determining a touch of a

button.

00 : no debounce, use incoming sample (default)

01 : 2 samples debounce

10 : 3 samples debounce

11 : 4 samples debounce

0x23 BtnAvgThresh 7:0 Defines the positive threshold for disabling the processing filter averaging (one

value for all buttons and proximity).

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

0x00: 0

0x01: 4

…

0x50: 320 (default)

…

0xFF: 1020

0x24 BtnCompNegThresh 7:0 Defines the negative offset compensation threshold (one value for all buttons and

proximity).

0x00: 0

0x01: 4

…

0xA0: 640 (default)

…

0xFF: 1020

0x25 BtnCompNegCntMax 7:0 Defines the number of ticks (below the negative offset compensation threshold)

which will initiate an offset compensation (one value for all buttons and proximity).

0x00: reserved

0x01: 1 sample (default)

…

0xFF: 255 samples

0x26 BtnHysteresis 7:0 Defines the button hysteresis corresponding to a percentage of the CAP

thresholds (defined in Table 15).

All buttons use the same hysteresis.

0x00: 0%

0x01: 1%

…

0x0A: 10% (default)

…

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Button Parameters

Address Name Bits Description

0x64: 100%

0x27 BtnStuckAtTimeout 7:0 Defines the stuck at timeout for buttons and proximity.

0x00: OFF (default)

0x01: 1 second

…

0xFF: 255 seconds

0x28 BtnStrongestHysteresis 7:0 Defines the hysteresis value for the strongest button filtering engine. This

parameter is only valid when BtnCfg has been configured to “report the strongest

touch”. The proximity sensor is excluded.

The hysteresis element eliminates the jittery output due to environmental noise

when two CAP sensors (configured as buttons) have values very close to each

other. The BtnStrongestHysteresis defines how much bigger the signal of the

second sensor needs to be compared to the strongest detected sensor, before the

second sensor becomes the strongest detected touch.

0x00: 0

0x01: 1

…

0x80: 128 (default)

…

0xFF: 255

0x29 BtnLongPressTimer 7:0 Defines the long press button timeout on AOI pins (applicable in Single Reporting

Mode). The proximity sensor does not trigger the timer.

0x00: OFF (default)

0x01: 1 second

…

0xFF: 255 seconds

Table 20 Button Parameters

The buttons and the proximity sensor operate in a similar way although some parameters can be set uniquely for

buttons or the proximity sensor only (according the previous tables describing the button and proximity

parameters).

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

Figure 53 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.

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ticks_diff

Figure 53 Touch and Release Example

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

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

In the example of Figure 53 the touch is validated after 2 ticks (BtnCfg [2:0] = 1).

The release is detected immediately (BtnCfg [3] = 0) at the first tick which is below the threshold minus the

hysteresis.

BtnCfg

The SX8661 button and proximity interface has three modes of operation:

• Report All: reports all touches of multiple fingers and proximity detection.

• Report Single: reports only a single touch and/or proximity. Subsequent touches are ignored until the

first touch is released. On the AOI proximity is implicit in case of a button touch.

• Report Strongest: reports the strongest touch. When the signal from another sensor rises above the

first sensor’s signal, the second sensor is then reported instead. On the AOI proximity is implicit in

case of a button touch.

Table 21 resumes the relation of reporting modes and information on the interfaces.

Reporting

Mode I2C AOI GPIOs (LEDs) Buzzer

All Buttons and Proximity Forced to Idle Buttons and

Proximity Button

Single Proximity or

1 Button and Proximity

Idle or 1 Button or

Proximity

Buttons and

Proximity Button

Strongest Proximity or

1 Button and Proximity

Idle or 1 Button or

Proximity

Buttons and

Proximity Button

Table 21 Reporting modes

The user can select to have the interrupt signal (INTB) on touching a button (proximity detected), releasing a

button (out of proximity) or both.

In noisy environments it may be required to debounce the touch and release detection decision.

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In case the debounce is enabled the SX8661 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.

BtnAvgPosThresh

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

BtnAvgPosThresh. 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 BtnAvgPosThresh value simultaneously then the SX8661 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 54.

ticks_diff

Figure 54 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:

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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.

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

compensation will be performed and button hence considered released, even if the finger remains on the

button 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.

BtnStrongestHysteresis

This parameter defines the hysteresis value for the adjacent button filtering engine. This parameter is only

valid when BtnCfg has been configured to report the strongest touch.

When the SX8661 device has been configured to report the strongest touch, a situation may arise where the

CAP signals of two sensors are of approximately equal value. Environmental noise can cause the signals of

these two sensors to fluctuate as shown in Figure 55 (b).

As a result of that, the output of the SX8661 device would also change very quickly as each of the two sensors

becomes the sensor with the strongest touch value. To eliminate this jitter, the SX8661 device adds a

hysteresis element to the calculation of the strongest touch sensor. In that respect, the strongest CAP sensor

is calculated as the sensor whose value is greater that the second detected strongest CAP sensor by the

Strongest hysteresis amount.

For example, as shown in Figure 55, the strongest CAP sensor is initially CAP0 (Figure 55 (b)). CAP1

becomes the strongest detected touch only if at some point in time the following holds true:

CAP1 signal = CAP0 signal + StrongestHysteresis

Similarly, if CAP2 is now also touched, it will only become the strongest detected touch if:

CAP2 signal = CAP1 signal + StrongestHysteresis.

BtnLongPressTimer

Figure 55 Strongest touch and Hysteresis

(a) (b)

Fluctuation

Strongest

Hysteresis

CAP1

CAP0

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This timer defines the time in seconds that the AOI will put out a voltage level corresponding to the button

touched. The timer is applicable in the Single Reporting Mode. After the timer expires the AOI will return to the

idle level even if the button is still touched.

The I2C status and GPO are not affected by this timer (i.e. they will be updated when the button is actually

released).

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5.6 Analog Output Interface Parameters

Analog Output Interface (AOI) Parameters

Address Name Bits Description

7:6 Reserved (0x00).

5:4 Defines AoiLevelDuringBuzzer (same for A&B).

0x00: AOI button level (default)

0x01: AOI Idle level

0x10: min level (0V)

0x11: max level( VDD)

3 Defines Aoi pwm period (same for A&B).

0: 0xFF (255) (default)

1: 0x3F (63)

0x2B AoiCfg

2:0 Reserved (0x01)

Button[7]

Button[6]

Button[5]

0x2C AoiBtnMapMsb 7:0

Button[4]

Button[3]

Button[2]

Button[1]

0x2D AoiBtnMapLsb 7:0

Button[0] or Proximity

Maps a button touch to one of the two Analog Output

Interfaces (AOI-A / AOI-B), or both.

00 : None

01 : AOI-A (GPIO7)

10 : AOI-B (GPIO6)

11 : Both

Default: 0x5555, i.e. Btn[7..0] mapped on AOI-A

0x2E AoiLevelBtn0 7:0

0x2F AoiLevelBtn1 7:0

0x30 AoiLevelBtn2 7:0

0x31 AoiLevelBtn3 7:0

0x32 AoiLevelBtn4 7:0

0x33 AoiLevelBtn5 7:0

0x34 AoiLevelBtn6 7:0

0x35 AoiLevelBtn7 7:0

0x36 AoiLevelIdle 7:0

Defines the level index (cf Table 8) for Buttons, Idle or Proximity (for CAP0)

The level index should be smaller or equal to Aoi pwm period as defined in

AoiCfg[3].

0x00: 0

0x01: 1

…

0xFF: 255

Default AoiLevelBtn0: 0xFF

Default AoiLevelBtn1: 0x2E

Default AoiLevelBtn2: 0x45

Default AoiLevelBtn3: 0x5D

Default AoiLevelBtn4: 0x74

Default AoiLevelBtn5: 0x8B

Default AoiLevelBtn6: 0xA3

Default AoiLevelBtn7: 0xBA

Default AoiLevelIdle: 0xFF.

Table 22 AOI Parameters

AoiBtnMap

This register is used to map the available buttons to SWI-A, AOI-B or both. For example, to map buttons 0 to 3

and buttons 4 to 7 on AOI-B, write the following value to the AoiPwmBtnMap register

AoiCfg = 0xAA55;

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AoiLevelBtn0, AoiLevelBtn1, AoiLevelBtn2, AoiLevelBtn3, AoiLevelBtn4, AoiLevelBtn5, AoiLevelBtn6,

AoiLevelBtn7, AoiLevelIdle

These registers define the level that will be output on AOI-A or AOI-B (depending on button mapping) when the

corresponding button is touched or when the corresponding state is active or idle. The duty cycle is defined as

a number of steps.

The mean voltage of a PWM signal is given by:

Mean voltage ≈ (AoiLevelBtnx / AoiPmwPeriod) * Maximum Voltage (VDD)

or:

AoiLevelBtnx ≈ (Mean voltage / Maximum Voltage (VDD)) * AoiPmwPeriod

AoiPwmPeriod is 255 or 63.

Example:

When button 0 is touched the desired AOI voltage is 0.30 Volts.

To calculate the AoiLevelBtnx is as follows (with AoiPwmPeriod=255):

Assuming a 3.3V VDD:

AoiLevelBtnx ≈ (Mean voltage / Maximum Voltage (VDD)) * AoiPmwPeriod

≈ (0.3/3.3) * 255 ≈ 23 decimal

Write 0x17 in the register AoiBtn0DutyCycle.

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5.7 Buzzer Parameters

Buzzer Parameters

Address Name Bits Description

7:6 Defines the phase 1 duration.

0x00: ~ 5ms

0x01: ~ 10ms

0x02: ~ 15ms (default)

0x03: ~ 30ms

5:4 Defines the phase 2 duration.

0x00: ~ 5ms

0x01: ~ 10ms

0x02: ~ 15ms (default)

0x03: ~ 30ms

3 Defines the buzzer idle level (BuzzerLevelIdle).

0x0: min level (0V), (default)

0x1: max level (VDD)

0x37 BuzzerCfg

2:0 Defines the buzzer pwm prescaler value.

Default: 0x04

0x38 BuzzerFreqPhase1 7:0 Defines the frequency for the first phase of the buzzer.

freq ≈ 4MHz /(2^prescaler * BuzzerFreqPhase1)

Default: 0x40 (4KHz)

0x39 BuzzerFreqPhase2 7:0 Defines the frequency for the second phase of the buzzer.

freq ≈ 4MHz /(2^prescaler * BuzzerFreqPhase2)

Default: 0x20 (8KHz)

0x3A Reserved 7:0 Reserved (0x00)

Table 23 Buzzer Parameters

The buzzer parameters are described in section 3.7.

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5.8 Mapping Parameters

Mapping Parameters

Address Name Bits Description

7:4 GPIO[7] Default: 0x0 0x3B MapAutoLight0

3:0 GPIO[6] Default: 0x7

7:4 GPIO[5] Default: 0x6 0x3C MapAutoLight1

3:0 GPIO[4] Default: 0x5

7:4 GPIO[3] Default: 0x4 0x3D MapAutoLight2

3:0 GPIO[2] Default: 0x3

7:4 GPIO[1] Default: 0x2 0x3E MapAutoLight3

3:0 GPIO[0] Default: 0x1

Defines the mapping between GPOs (with

Autolight ON) and sensor events.

0x00: Btn0 or Proximity

0x01: Btn1

…

0x07: Btn7

0x08…0x0B: Reserved

0x0C: Group0 as defined by MapAutoLightGrp0

0x0D: Group1 as defined by MapAutoLightGrp1

0x0E: Reserved

0x0F: Reserved

Several GPOs can be mapped to the same sensor

event and will be controlled simultaneously.

0x3F MapAutoLightGrp0Msb 7:0 Reserved (0x00)

7 Btn7

6 Btn6

5 Btn5

4 Btn4

3 Btn3

2 Btn2

1 Btn1

0x40 MapAutoLightGrp0Lsb

0 Btn0 or Proximity

Defines Group0 sensor events:

0: OFF

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.

Default: 0x00

0x41 MapAutoLightGrp1Msb 7:0 Reserved (0x00)

7 Btn7

6 Btn6

5 Btn5

4 Btn4

3 Btn3

2 Btn2

1 Btn1

0x42 MapAutoLightGrp1Lsb

0 Btn0 or Proximity

Defines Group1 sensor events:

0: OFF

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.

Default: 0x00

Table 24 Mapping Param eters

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).

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Table 25 defines for each selectable sensor event, which action will trigger corresponding GPO to switch ON

or OFF.

MapAutoLight GPO ON GPO OFF

BtnX Touch Release

Table 25 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 (i.e. Group0).

- MapAutoLightGrp0 should be set to 0x0003 (i.e. Btn0 or Btn1)

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5.9 GPIO Parameters

GPIO Parameters

Address Name Bits Description

7:6 GPIO[7] Mode Default AOI-A

5:4 GPIO[6] Mode Default GPO

3:2 GPIO[5] Mode Default GPO

0x43 GpioMode7_4

1:0 GPIO[4] Mode Default GPO

7:6 GPIO[3] Mode Default GPO

5:4 GPIO[2] Mode Default GPO

3:2 GPIO[1] Mode Default GPO

0x44 GpioMode3_0

1:0 GPIO[0] Mode

Defines the GPIO mode.

00: GPO

01: GPP

10: Reserved

11: SPO: AOI-A for GPIO[7],

AOI-B for GPIO[6],

Buzzer for GPIO[5]),

Reserved for GPIO[4..0]

Default: 0xC000

Default GPO

0x45 GpioIntensityOn0 7:0

0x46 GpioIntensityOn1 7:0

0x47 GpioIntensityOn2 7:0

0x48 GpioIntensityOn3 7:0

0x49 GpioIntensityOn4 7:0

0x4A GpioIntensityOn5 7:0

0x4B GpioIntensityOn6 7:0

0x4C GpioIntensityOn7 7:0

Defines the ON intensity index.

0x00: 0

0x01: 1

…

0xFF: 255 (default)

0x4D GpioIntensityOff0 7:0

0x4E GpioIntensityOff1 7:0

0x4F GpioIntensityOff2 7:0

0x50 GpioIntensityOff3 7:0

0x51 GpioIntensityOff4 7:0

0x52 GpioIntensityOff5 7:0

0x53 GpioIntensityOff6 7:0

0x54 GpioIntensityOff7 7:0

Defines the OFF intensity index.

0x00: 0

0x01: 1

…

0xFF: 255 (default)

0x56 GpioOutPwrUp 7:0 Defines the values of GPO and GPP pins after power up i.e. default values of

I2C parameters GpoCtrl and GppIntensity respectively.

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.

0: OFF(GPO) / IntensityOff (GPP)

1: ON (GPO) / IntensityOn (GPP)

Default: 0x00

0x57 GpioAutoLight 7:0 Enables Autolight in GPO mode.

0 : OFF

1 : ON

Default: 0xFF

0x58 GpioPolarity 7:0 Defines the polarity of the GPO and GPP pins.

SPO pins require Normal Polarity.

0: Inverted

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GPIO Parameters

Address Name Bits Description

1: Normal

Default: 0x80

0x59 GpioFunction 7:0 Defines the intensity index vs PWM pulse width function.

0: Logarithmic

1: Linear

Default: 0x80

0x5A GpioIncFactor 7:0 Defines the fading increment factor.

0: intensity index incremented every increment time

1: intensity index incremented every 16 increment times

Default: 0x00

0x5B GpioDecFactor 7:0 Defines the fading decrement factor.

0: intensity index decremented every decrement time

1: intensity index decremented every 16 decrement times

Default: 0x00

7:4 GPIO[7] Fading Increment Time 0x5C GpioIncTime7_6

3:0 GPIO[6] Fading Increment Time

7:4 GPIO[5] Fading Increment Time 0x5D GpioIncTime5_4

3:0 GPIO[4] Fading Increment Time

7:4 GPIO[3] Fading Increment Time 0x5E GpioIncTime3_2

3:0 GPIO[2] Fading Increment Time

7:4 GPIO[1] Fading Increment Time 0x5F GpioIncTime1_0

3:0 GPIO[0] Fading Increment Time

Defines the fading increment time.

0x0: OFF

0x1: 0.5ms

0x2: 1ms

…

0xF: 7.5ms

The total fading in time will be:

GpioIncTime*GpioIncFactor*

(GpioIntensityOn – GpioIntensityOff)

Default: 0x11111111

7:4 GPIO[7] Fading Decrement Time 0x60 GpioDecTime7_6

3:0 GPIO[6] Fading Decrement Time

7:4 GPIO[5] Fading Decrement Time 0x61 GpioDecTime5_4

3:0 GPIO[4] Fading Decrement Time

7:4 GPIO[3] Fading Decrement Time 0x62 GpioDecTime3_2

3:0 GPIO[2] Fading Decrement Time

7:4 GPIO[1] Fading Decrement Time 0x63 GpioDecTime1_0

3:0 GPIO[0] Fading Decrement Time

Defines the fading decrement time.

0x0: OFF

0x1: 0.5ms

0x2: 1ms

…

0x4: 2.0ms

…

0xF: 7.5ms

The total fading out time will be:

GpioDecTime*GpioDecFactor*

(GpioIntensityOn – GpioIntensityOff)

Default: 0x44444444

7:4 GPIO[7] OFF Delay 0x64 GpioOffDelay7_6

3:0 GPIO[6] OFF Delay

7:4 GPIO[5] OFF Delay 0x65 GpioOffDelay5_4

3:0 GPIO[4] OFF Delay

7:4 GPIO[3] OFF Delay 0x66 GpioOffDelay3_2

3:0 GPIO[2] OFF Delay

7:4 GPIO[1] OFF Delay 0x67 GpioOffDelay1_0

3:0 GPIO[0] OFF Delay

Single Fading Mode

Defines the delay between release and start

of fading out.

0x0: instantaneous

0x1: 200 ms

0x2: 400 ms

0x3: 600ms

…

0xA: 2s

0xB: 4s

…

0xF: 12s

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GPIO Parameters

Address Name Bits Description

Default: 0x00000000

7:6 GPIO[7] Pullup/down

5:4 GPIO[6] Pullup/down

3:2 GPIO[5] Pullup/down

0x68 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

0x69 GpioPullUpDown3_0

1:0 GPIO[0] Pullup/down

Enables pullup/down resistors for GPIO pins.

00 : None

01 : Pullup

10 : Pulldown

11 : Reserved

Default: 0x0000

0x6A Reserved 7:0 Reserved (0x00)

0x6B Reserved 7:0 Reserved (0x00)

0x6C Reserved 7:0 Reserved (0x00)

7:6 Fading mode for GPIO[7]

5:4 Fading mode for GPIO[6]

3:2 Fading mode for GPIO[5]

0x6D GpioFadingMode7_4

1:0 Fading mode for GPIO[4]

7:6 Fading mode for GPIO[3]

5:4 Fading mode for GPIO[2]

3:2 Fading mode for GPIO[1]

0x6E GpioFadingMode3_0

1:0 Fading mode for GPIO[0]

Defines the Fading mode for GPO[7:0].

00: Single Fading Mode

01: Continuous Fading Mode

10: Reseved

11: Reserved

Default: 0x0000

The fading modes are expected to be

defined at power up by the QSM or NVM.

In case the fading modes need to be

changed after power up this can be done

when the GPOs are all OFF.

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Table 26 resumes the applicable SPM and I2C parameters for each GPIO mode.

GPP GPO SPO

GpioMode X X X5

GpioOutPwrUp X1 X2,3

GpioAutolight X

GpioPolarity X X

GpioIntensityOn X1 X

GpioIntensityOff X1 X

GpioFunction X X

GpioIncFactor X

GpioDecFactor X

GpioIncTime X

GpioDecTime X

GpioOffDelay X

SPM

GpioPullUpDown

IrqSrc[4]

GpoCtrl X

GppPinId X

I2C

GppIntensity X1

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

corresponding bits value.

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

3 GpioOutPwrUp must be set to OFF in Continuous Fading Mode (with Autolight OFF)

4 Only if Autolight is OFF, else ignored

5 In SPO mode assure the following settings: GpioOutPwrUp=OFF, GpioAutoLight=ON, GpioPolarity=Normal, GpioFunction=Linear

Table 26 Appl icable SPM/ I2C Parameters vs. GPIO Mode

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6 I2C INTERFACE

The I2C implemented on the SX8661 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, 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 SX8661 is powered down.

The SPM can be stored permanently in the NVM memory of the SX8661. 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 56.

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

SX8661 then acknowledges [A] that it is being addressed, and the master sends an 8 bit Data Byte consisting of

the SX8661 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 56 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 57.

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

SX8661 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 SX8661 responds with acknowledge [A] and the Read Data byte (RD0). If the master needs to read more

data it will acknowledge [A] and the SX8661 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 57 I2C read

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6.3 I2C Registers Overview

Address Name R/W Description

0x00 IrqSrc read Interrupt Source

0x01 Reserved

0x02 CapStat read Button Status

0x03 Reserved

0x04 Reserved

0x05 Reserved

0x06 Reserved

0x07 Reserved

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 27 I2 C Regist er s 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 Reserved

3 Reserved

2 Buttons/Proximity 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 28 I nt errupt Source

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

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

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

IrqSrc[2] is set if a Button/Proximity event occurred (touch or release if enabled). 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 via host request. CompOpmode shows the current

operation mode.

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Address Name Bits Description

7 Status button 7

6 Status button 6

5 Status button 5

4 Status button 4

3 Status button 3

2 Status button 2

1 Status button 1

0x02 CapStat

0 Status button 0

Status of individual buttons

0: Released (default)

1: Touched

Table 29 I 2C Cap st atus

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 30 I 2C SPM status

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6.5 Control Registers

Address Name Bits Description

7:3 Reserved*, write only ‘00000’

2 Compensation

Indicates/triggers compensation procedure

0: Compensation completed (default)

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

compensation

0x09 CompOpMode

1:0 Operating Mode

Indicates/programs** operating mode

00: Active mode (default)

01: Doze mode

10: Sleep mode

11: Reserved

* 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.

Table 31 I 2C com pensat ion, operation modes

Address Name Bits Description

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

Triggers ON/OFF state of GPOs when Autolight is OFF

0: OFF (i.e. go to IntensityOff)

1: ON (i.e. go to IntensityOn)

Default is set by SPM parameter GpioOutPwrUp

Bits of non-GPO pins are ignored.

Table 32 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 33 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 34 I2C GPP Intensity

Address Name Bits Description

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

Table 35 I2C Soft Reset

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6.6 SPM Gateway Registers

The SX8661 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

Defines the normal operation or SPM mode

00: I2C in normal operation mode (default)

01: I2C in SPM mode

10: Reserved

11: Reserved

Defines r/w direction of SPM

0: SPM write access (default)

1: SPM read access

0x0D SpmCfg

2:0 000: Reserved

Table 36 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 37 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 38 SPM Key MSB at I2C register address 0xAC

Address Name Bits Description

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

Table 39 SPM Key LSB

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6.6.1 SPM Write Sequence

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 58 SPM writ e sequence

The complete SPM can be written by repeating 16 times the cycles shown in Figure 58 using base addresses

0x00, 0x08, 0x10,…0x70, 0x78.

Once the SPM write sequence is actually applied, the INTB pin will be asserted. The host clears the interrupt by

reading any I2C register. At the same time the bit GenStatMsb[6], indicating the SPM write is done, will be

cleared.

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6.6.2 SPM Read Sequence

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 59 SPM Read Sequence

The complete SPM can be read by repeating 16 times the cycles shown in Figure 59 using base addresses 0x00,

0x08, 0x10,…0x70, 0x78.

Once the SPM read sequence is actually applied, the INTB pin will be asserted. The host clears the interrupt by

reading any I2C register. At the same time the bit GenStatMsb[6], indicating the SPM write is done, will be

cleared.

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

GenStatLsb[7:5].

Figure 60 Simplified Diagram NvmCycle

Figure 60 shows the simplified diagram of the NvmCycle counter. The SX8661 is delivered with empty NVM and

NvmCycle set to zero. The SPM points to the QSM.

Each NVM burn will increase the NvmCycle. At the fourth NVM burn the SX8661 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 61.

SSA 00x0EA0xA5A PA

S : Start condition

SA : Slave address

A : Slave acknowledge

P : Stop condition

From master to slave

From slave to master

SSA 00x0EA0x5AA PA

SSA 00xAC

A0x62A PA

SSA 00xADA0x9DA PA

Figure 61: NVM burn procedure

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7 APPLICATION INFORMATION

7.1 Triple proximity reporting

This section describes in further detail the quickstart application of chapter 3.1.

One AOI with seven LEDs are used. The intensity level of the LEDs show if proximity (medium intensity) or a

touch (maximum intensity) is detected. The LEDs are off in case no finger is present.

Figure 62 Typical Application ( one AOI), tr iple proximity reporting

In case of proximity all LEDs (d0 to d6) are enabled to a medium intensity.

If a sensor is touched then only the corresponding LED will light up with full intensity. The other LEDs remain at

medium intensity.

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7.2 Dual proximity reporting

Two AOIs and two LEDs are used. One LED is showing proximity and the second LED (or multiple LEDs) for

showing any touch.

Figure 63 Typical Application (tw o AOI), dual proximity reporting

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Figure 64 dual proximity LED and AOI reporting

Figure 64 shows the reporting on the LEDs and the AOI for the application with two AOIs.

On proximity all the LEDs (d1 to dx) are enabled to maximum light intensity.

A touch on any button is shown by the continuous fading in and fading out of the LED d0.

AOI-A AOI-B

prox idle idle

key1 0.6V idle

key2 0.9V idle

key3 1.2V idle

key4 idle 1.5V

key5 idle 1.8V

key6 idle 2.1V

key7 idle 2.4V

Table 40 exam ple AO I-A, AOIB

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7.2.1 SPM file (application two AOI, dual proximity reporting)

#Address[Hex] Value[Hex] #Address[Hex] Value[Hex]

0x00 0xxx 0x40 0xFE

0x01 0xxx 0x41 0x00

0x02 0x41 0x42 0x00

0x03 0xxx 0x43 0xF0

0x04 0x2B 0x44 0x00

0x05 0x02 0x45 0xFF

0x06 0x0D 0x46 0xFF

0x07 0x00 0x47 0xFF

0x08 0x00 0x48 0xFF

0x09 0x05 0x49 0xFF

0x0A 0x00 0x4A 0xFF

0x0B 0x55 0x4B 0xFF

0x0C 0x57 0x4C 0xFF

0x0D 0x73 0x4D 0x00

0x0E 0x33 0x4E 0x00

0x0F 0x33 0x4F 0x00

0x10 0x33 0x50 0x00

0x11 0x00 0x51 0x00

0x12 0x00 0x52 0x00

0x13 0xA0 0x53 0x00

0x14 0xA0 0x54 0x00

0x15 0xA0 0x55 0xFF

0x16 0xA0 0x56 0x00

0x17 0xA0 0x57 0xC3

0x18 0xA0 0x58 0xC0

0x19 0xA0 0x59 0xC0

0x1A 0xA0 0x5A 0x00

0x1B 0x00 0x5B 0x00

0x1C 0x00 0x5C 0x04

0x1D 0x00 0x5D 0x44

0x1E 0x0A 0x5E 0x44

0x1F 0x00 0x5F 0x44

0x20 0x70 0x60 0x00

0x21 0x50 0x61 0x44

0x22 0x50 0x62 0x44

0x23 0x01 0x63 0x44

0x24 0x0A 0x64 0x00

0x25 0x00 0x65 0xEE

0x26 0x80 0x66 0xEE

0x27 0x00 0x67 0xE0

0x28 0x00 0x68 0x00

0x29 0x00 0x69 0x00

0x2A 0xFF 0x6A 0x00

0x2B 0x01 0x6B 0x00

0x2C 0xAA 0x6C 0x00

0x2D 0x55 0x6D 0x00

0x2E 0xFF 0x6E 0x01

0x2F 0x2E 0x6F 0x50

0x30 0x45 0x70 0x74

0x31 0x5D 0x71 0x10

0x32 0x74 0x72 0x45

0x33 0x8B 0x73 0x03

0x34 0xA3 0x74 0xFF

0x35 0xBA 0x75 0xFF

0x36 0xFF 0x76 0xFF

0x37 0xA4 0x77 0xD5

0x38 0x40 0x78 0x55

0x39 0x20 0x79 0x55

0x3A 0x00 0x7A 0x7F

0x3B 0x00 0x7B 0x23

0x3C 0x00 0x7C 0x22

0x3D 0x00 0x7D 0x41

0x3E 0x0C 0x7E 0xFF

0x3F 0x00 0x7F 0x3D

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7.3 Example of Touch+Proximity Module

7.3.1 Overview

To demonstrate the proximity sensing feature of the SX8661/SX863x family, a module has been designed and is

illustrated in figure below.

Figure 65 Touch+Proximity Module Overview

The touch button controller is running in stand-alone (i.e. without host) and uses the Autolight mode to turn LEDs

ON/OFF accordingly to the touch buttons and proximity sensing status.

7.3.2 Operation

Module operation can be seen as 5 steps which are described in figure below

1. No finger

=> No proximity detected

=> All LEDs OFF

2. Finger approaches

=> Proximity detected

=> Blue LEDs turned ON

3. Button touch

=> Orange LED turned ON

(blue+orange = pink)

4. Button release

=> Orange LED turned

OFF

5. Finger removed

=> No proximity detected

=> Blue LEDs turned OFF

Figure 66 Touch+Proximity Module Operation

Notes:

- For better user experience, bicolor LEDs have been used here but one could decide to design a module with

normal unicolor LEDs. In this case, step 3 above would simply consist in a higher (blue) intensity for the LED of

the button touched.

- For obvious demonstration purposes the overlay used here is transparent but in typical applications (TV,

Monitor, Set-top box, etc) the overlay would be opaque enough so that when LEDs are OFF (i.e. no proximity

detected) the PCB is not visible to the user.

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7.3.3 Performance

The proximity sensing distance of detection has been measured in these conditions:

- CapProxEnable = ON

- CapSensitivity = 7 (Max)

- CapThreshold = 300

- Board main supplied and placed vertically i.e. same orientation as hand/finger

- Finger pointing center button

The results obtained are provided in table below:

Distance of Detection

Palm ~10cm

Finger (natural position) ~6cm

Orthogonal finger (worst case) ~4cm

Table 41 Proximity Sensing Distance of Detection

7.3.4 Schematics

Figure 67 Touch+Proximity Module Schematics

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7.3.5 Layout

Figure 68 Touch+Proximity Module Layout - Top

Figure 69 Touch+Proximity Module Layout - Mid1

Figure 70 Touch+Proximity Module Layout - Mid2

Figure 71 Touch+Proximity Module Layout - Bottom

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8 REFERENCES

[1] Capacitive Touch Sensing Layout guidelines on www.semtech.com

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9 PACKAGING INFORMATION

9.1 Package Outline Drawing

SX8661 is assembled in a MLPQ-UT28 package as shown in Figure 72.

INDICATOR

(LASER MARK)

PIN 1

DIMENSIONS

NOM

INCHES

bbb

aaa

DIM

MIN MAX

MILLIMETERS

MINMAX NOM

.154 .157 .161 3.90 4.00 4.10

.003

.006

.100

.008

.104

.000

.020

(.006)

0.08

0.20

.010

.108

0.15

2.55

.024

.001 0.00

0.50

2.75

0.25

2.65

0.02

0.60

(0.152)

.004 0.10

2.55 2.65 2.75

0.40 BSC.016 BSC

0.30.012 .020.016 0.40 0.50

.108.104.100

SEATING

PLANE

CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES).

COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS.

NOTES:

aaa C

LxN

E/2

bbb CAB

D/2

bxN

Figure 72 Package outline drawing

9.2 Land Pattern

The land pattern of MLPQ-UT28 package, 4 mm x 4 mm is shown in Figure 73.

Figure 73 Land pattern

ADV ANCED COMMUNICATIONS & SENSING DATASHEET

SX8661

Low Power, Capacitive Button Touch and Proximity Controller

(8 sensors) with LED Drivers and Analog Output

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