SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING GENERAL DESCRIPTION KEY PRODUCT FEATURES The SX8636 is an ultra low power, fully integrated 8channel solution for capacitive touch-buttons and proximity detection applications. Unlike many capacitive touch solutions, the SX8636 features dedicated capacitive sense inputs (that requires no external components) in addition to 8 general purpose I/O ports (GPIO). Each GPIO is typically configured as LED driver with independent PWM source for enhanced lighting control such as intensity and fading. Complete eight Sensors Capacitive Touch Controller for The SX8636 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. Buttons Pre-configured for eight Buttons Eight LED Drivers with Individual Intensity, Fading Control and Autolight Mode 256 steps PWM Linear and Logarithmic control Proximity Sensing up to several centimetres High Resolution Capacitive Sensing Up to 100pF of Offset Capacitance Compensation at Full Sensitivity Capable of Sensing through Overlay Materials up to 5mm thick Extremely Low Power Optimized for Portable Application 8uA (typ) in Sleep Mode 80uA (typ) in Doze Mode (Scanning Period 195ms) 175uA (typ) in Active Mode (Scanning Period 30ms) Programmable Scanning Period from 15ms to 1500ms The SX8636 incorporates a versatile firmware that was specially designed to simplify capacitive touch solution design and offers reduced time-to-market. Integrated multi-time programmable memory provides the ultimate flexibility to modify key firmware parameters (gain, threshold, scan period, auto offset compensation… ) in the field without the need for new firmware development. Auto Offset Compensation Eliminates False Triggers due to Environmental Factors (Temperature, Humidity) Initiated on Power-up and Configurable Intervals Multi-Time In-Field Programmable Firmware Parameters for Ultimate Flexibility On-chip user programmable memory for fast, self contained start-up The SX8636 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. "Smart" Wake-up Sequence for Easy Activation from Doze No External Components per Sensor Input Internal Clock Requires No External Components Differential Sensor Sampling for Reduced EMI 400 KHz Fast-Mode I²C Interface with Interrupt -40°C to +85°C Operation TYPICAL APPLICATION CIRCUIT APPLICATIONS Notebook/Netbook/Portable/Handheld computers Cell phones, PDAs Consumer Products, Instrumentation, Automotive Mechanical Button Replacement ORDERING INFORMATION Part Number Temperature Range Package SX8636I05AULTRT1 -40°C to +85°C Lead Free MLPQ-UT28 1 3000 Units/reel * This device is RoHS/WEEE compliant and Halogen Free Revision 7_6, June 12 © 2012 Semtech Corp. 1 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Table of Contents GENERAL DESCRIPTION ........................................................................................................................ 1 TYPICAL APPLICATION CIRCUIT ............................................................................................................ 1 KEY PRODUCT FEATURES..................................................................................................................... 1 APPLICATIONS....................................................................................................................................... 1 ORDERING INFORMATION...................................................................................................................... 1 1 GENERAL DESCRIPTION............................................................................................................... 4 1.1 1.2 1.3 1.4 1.5 2 Pin Diagram Marking information Pin Description Simplified Block Diagram Acronyms 4 4 5 6 6 ELECTRICAL CHARACTERISTICS ................................................................................................. 7 2.1 2.2 2.3 2.4 3 Absolute Maximum Ratings Recommended Operating Conditions Thermal Characteristics Electrical Specifications 7 7 7 8 FUNCTIONAL DESCRIPTION ........................................................................................................ 10 3.1 3.2 Quickstart Application Introduction 3.2.1 General 3.2.2 GPIOs 3.2.3 Parameters 3.2.4 Configuration 3.3 Scan Period 3.4 Operation modes 3.5 Sensors on the PCB 3.6 Button Information 3.6.1 Button Information 3.7 Analog Sensing Interface 3.8 Offset Compensation 3.9 Processing 3.10 Configuration 3.11 Power Management 3.12 Clock Circuitry 3.13 I2C interface 3.14 Reset 3.14.1 Power up 3.14.2 RESETB 3.14.3 Software Reset 3.15 Interrupt 3.15.1 Power up 3.15.2 Assertion 3.15.3 Clearing 3.15.4 Example Revision 7_6, June 12 10 10 10 11 11 11 12 12 14 14 14 15 16 17 17 19 19 19 20 20 20 21 22 22 22 22 23 © 2012 Semtech Corp. 2 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.16 General Purpose Input and Outputs 3.16.1 Introduction and Definitions 3.16.2 GPI 3.16.3 GPP 3.16.4 GPO 3.16.5 Intensity index vs PWM pulse width 3.17 Smart Wake Up 4 23 23 24 24 25 28 29 PIN DESCRIPTIONS ..................................................................................................................... 30 4.1 4.2 4.3 4.4 4.5 5 Introduction ASI pins Host interface pins Power management pins General purpose IO pins 30 30 31 34 35 DETAILED CONFIGURATION DESCRIPTIONS .............................................................................. 36 5.1 5.2 5.3 5.4 5.5 5.6 6 Introduction General Parameters Capacitive Sensors Parameters Button Parameters Mapping Parameters GPIO Parameters 36 39 40 44 48 50 I2C INTERFACE ........................................................................................................................... 54 6.1 6.2 6.3 6.4 6.5 6.6 I2C Write I2C read I2C Registers Overview Status Registers Control Registers SPM Gateway Registers 6.6.1 SPM Write Sequence 6.6.2 SPM Read Sequence 6.7 NVM burn 6.8 Monitor Mode 7 54 55 56 57 59 61 62 63 64 65 APPLICATION INFORMATION ...................................................................................................... 66 7.1 7.2 Typical Application Schematic Example of Touch+Proximity Module 7.2.1 Overview 7.2.2 Operation 7.2.3 Performance 7.2.4 Schematics 7.2.5 Layout 66 67 67 67 67 68 69 8 REFERENCES ............................................................................................................................. 70 9 PACKAGING INFORMATION ........................................................................................................ 71 9.1 9.2 Package Outline Drawing Land Pattern Revision 7_6, June 12 71 71 © 2012 Semtech Corp. 3 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 1 GENERAL DESCRIPTION cap4 4 cap5 5 cap6 6 cap7 7 vana resetb gnd vdig gpio7 gpio6 23 22 SX8636 Top View bottom ground pad 8 9 10 11 12 13 14 gpio0 3 24 sda cap3 25 scl 2 26 intb cap2 27 vdd 1 28 cp cap1 cap0 Pin Diagram cn 1.1 21 gnd 20 gpio5 19 gpio4 18 gpio3 17 gpio2 16 gnd 15 gpio1 Figure 1 Pinout Diagram 1.2 Marking information FM26 yyww xxxxx R05 yyww = Date Code xxxxx = Semtech lot number R05 = Semtech Code Figure 2 Marking Information Revision 7_6, June 12 © 2012 Semtech Corp. 4 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 1.3 Pin Description Number Name Type Description 1 CAP1 Analog Capacitive Sensor 1 2 CAP2 Analog Capacitive Sensor 2 3 CAP3 Analog Capacitive Sensor 3 4 CAP4 Analog Capacitive Sensor 4 5 CAP5 Analog Capacitive Sensor 5 6 CAP6 Analog Capacitive Sensor 6 7 CAP7 Analog Capacitive Sensor 7 8 CN Analog Integration Capacitor, negative terminal (1nF between CN and CP) 9 CP Analog Integration Capacitor, positive terminal (1nF between CN and CP) 10 VDD Power Main input power supply 11 INTB Digital Output Interrupt, active LOW, requires pull up resistor (on host or external) 12 SCL Digital Input I2C Clock, requires pull up resistor (on host or external) 13 SDA Digital Input/Output I2C Data, requires pull up resistor (on host or external) 14 GPIO0 Digital Input/Output General Purpose Input/Output 0 15 GPIO1 Digital Input/Output General Purpose Input/Output 1 16 GND Ground Ground 17 GPIO2 Digital Input/Output General Purpose Input/Output 2 18 GPIO3 Digital Input/Output General Purpose Input/Output 3 19 GPIO4 Digital Input/Output General Purpose Input/Output 4 20 GPIO5 Digital Input/Output General Purpose Input/Output 5 21 GND Ground Ground 22 GPIO6 Digital Input/Output General Purpose Input/Output 6 23 GPIO7 Digital Input/Output General Purpose Input/Output 7 24 VDIG Analog Digital Core Decoupling, connect to a 100nF decoupling capacitor 25 GND Ground Ground 26 RESETB Digital Input Active Low Reset. Connect to VDD if not used. 27 VANA Analog Analog Core Decoupling, connect to a 100nF decoupling capacitor 28 CAP0 Analog Capacitive Sensor 0 Ground Exposed pad connect to ground bottom plate GND Table 1 Pin description Revision 7_6, June 12 © 2012 Semtech Corp. 5 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 1.4 Simplified Block Diagram gpo7 gpo6 scl sda vdig intb gnd vdd cp cn vana resetb The simplified block diagram of the SX8636 is illustrated in Figure 3. Figure 3 Simplified block diagram of the SX8636 1.5 ASI DCV GPI GPO GPP MTP NVM PWM QSM SPM Acronyms Analog Sensor Interface Digital Compensation Value General Purpose Input General Purpose Output General Purpose PWM Multiple Time Programmable Non Volatile Memory Pulse Width Modulation Quick Start Memory Shadow Parameter Memory Revision 7_6, June 12 © 2012 Semtech Corp. 6 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 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 ESDHBM 3 kV ILU ± 100 mA ESD HBM (Human Body model) Latchup (i) (ii) Table 2 Absolute Maximum Ratings (i) Tested to JEDEC standard JESD22-A114 (ii) Tested to JEDEC standard JESD78 2.2 Recommended Operating Conditions Parameter Symbol Min. Max. Unit Supply Voltage VDD 2.7V 3.6 V 100 mV Supply Voltage Drop (iii, iv, v) VDDdrop Supply Voltage for NVM programming VDD 3.0V 3.6 V Ambient Temperature Range TA -40 85 °C Table 3 Recommended Operating Conditions (iii) Performance for 2.6V < VDD < 2.7V might be degraded. (iv) Operation is not guaranteed below 2.6V. Should VDD briefly drop below this minimum value, then the SX8636 may require; - a hardware reset issued by the host using the RESETB pin - a software reset issued by the host using the I2C interface (v) In the event the host processor is reset or undergoes a power OFF/ON cycle, it is recommended that the host also resets the SX8636 and assures that parameters are re-written into the SPM (should these differ to the parameters held in NVM). 2.3 Thermal Characteristics Parameter Thermal Resistance - Junction to Ambient Symbol (vi) θJA Min. Max. Unit 25 °C/W Table 4 Thermal Characteristics (vi) Static airflow Revision 7_6, June 12 © 2012 Semtech Corp. 7 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 2.4 Electrical Specifications All values are valid within the operating conditions unless otherwise specified. Parameter Symbol Conditions Active mode, average IOP,active Doze mode, average Sleep Min. Typ. Max. Unit 30ms scan period, 8 sensors enabled, minimum sensitivity 175 225 uA IOP,Doze 195ms scan period, 8 sensors enabled, minimum sensitivity 80 110 uA IOP,sleep I2C and GPI listening, sensors disabled 8 17 uA Current consumption GPIO, set as Input, RESETB, SCL, SDA Input logic high VIH 0.7*VDD VDD + 0.3V V Input logic low VIL VSS applied to GND pins VSS - 0.3V 0.8 V Input leakage current LI CMOS input ±1 uA Pull up resistor RPU when enabled 660 kΩ Pull down resistor RPD when enabled 660 kΩ Output logic high VOH IOH <4mA Output logic low VOL IOL,GPIO<12mA IOL,SDA,INTB<4mA 0.4 V tpor time between rising edge VDD and rising INTB 150 ms GPIO set as Output, INTB, SDA VDD-0.4 V Start-up Power up time RESETB Pulse width tres 50 ns 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 Electrical Specifications Revision 7_6, June 12 © 2012 Semtech Corp. 8 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Parameter I2C Timing Specifications Symbol Conditions Min. Typ. Max. Unit 400 KHz (i) SCL clock frequency fSCL 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 I2C Timing 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 timing Figure 5 I2C Data timing Revision 7_6, June 12 © 2012 Semtech Corp. 9 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3 FUNCTIONAL DESCRIPTION 3.1 Quickstart Application The SX8636 is preconfigured (Quickstart Application) for an application with eight buttons and eight LED drivers using logarithmic PWM fading. Implementing a schematic based on Figure 6 will be immediately operational after powering without programming the SX8636 (even without host). cap1 d1 cap2 gpo6 SX8636 cap0 d0 gpo7 vdig gnd vana resetb d7 analog sensor interface clock generation RC PWM LED controller d6 gnd gpo5 d5 gpo4 d4 d2 cap3 power management d3 gpo3 cap4 d4 cap5 d5 cap6 micro processor GPIO controller gpo2 RAM NVM gpo1 ROM I2C d6 cap7 d3 d2 gnd d1 gpo0 d0 bottom plate sda scl intb vdd cp cn d7 HOST Figure 6 Quickstart Application Touching the sensor on the CAP0 pin will enable automatically the LED connected to GPIO0. When the CAP0 sensor is released the LED on GPIO0 will slowly fade-out using smooth logarithmic fading. All other sensors (CAP1 to CAP7) have their own LED associated on a GPIO pin showing a touch or a release. The sensor detection and the LED fading described above are operational without any host interaction. This is made possible using the SX8636 Autolight feature described in the following sections. 3.2 3.2.1 Introduction General The SX8636 is intended to be used in applications which require capacitive sensors covered by isolating overlay material and which need to detect the proximity of a finger/hand though the air. A finger approaching the capacitive sensors will change the charge that can be loaded on the sensors. The SX8636 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 SX8636 Analog Sensor Interface (ASI). The ticks are further processed by the SX8636 and converted in a high level, easy to use information for the user’s host. The information between SX8636 and the user’s host is passed through the I2C interface with an additional interrupt signal indicating that the SX8636 has new information. For buttons this information is simply touched or released. Revision 7_6, June 12 © 2012 Semtech Corp. 10 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.2.2 GPIOs A second path of feedback to the user is using General Purpose Input Output (GPIO) pins. The SX8636 offers eight individual configurable GPIO pins. The GPIO can e.g. be set as a LED driver which slowly fade-in when a finger touches a button and slowly fade-out when the button is released. Fading intensity variations can be logarithmic or linear. Interval speed and initial and final light intensity can be selected by the user. The fading is done using a 256 steps PWM. The SX8636 has eight individual PWM generators, one for each GPIO pin. The LED fading can be initiated automatically by the SX8636 by setting the SX8636 Autolight feature. A simple touch on a sensor and the corresponding LED will fade-in without any host interaction over the I2C. In case the Autolight feature is disabled then the host will decide to start a LED fading-in period, simply by setting the GP0 pin to ‘high’ using one I2C command. The SX8636 will then slowly fade-in the LED using the PWM autonomously. In case the host needs to have full control of the LED intensity then the host can set the GPIO in GPP mode. The host is then able to set the PWM pulse width freely at the expense of an increased I2C occupation. The GPIOs can be set further in the digital standard Input mode (GPI). 3.2.3 Parameters The SX8636 has many low level built-in, fixed algorithms and procedures. To allow a lot of freedom for the user and adapt the SX8636 for different applications these algorithms and procedures can be configured with a large set of parameters which will be described in the following sections. Examples of parameters are which sensors are buttons, which GPIO is used for outputs or LEDs and which GPIO is mapped to which button. Sensitivity and detection thresholds of the sensors are part of these parameters. Assuming that overlay material and sensors areas are identical then the sensitivities and thresholds will be the same for each sensor. In case sensors are not of the same size then sensitivities or thresholds might be chosen individually per sensor. So a smaller size sensor can have a larger sensitivity while a big size sensor may have the lower sensitivity. 3.2.4 Configuration During a development phase the parameters can be determined and fine tuned by the users and downloaded over the I2C in a dynamic way. The parameter set can be downloaded over the I2C by the host each time the SX8636 boots up. This allows a flexible way of setting the parameters at the expense of I2C occupation. In case the parameters are frozen they can be programmed in Multiple Time Programmable (MTP) Non Volatile Memory (NVM) on the SX8636. The programming needs to be done once (over the I2C). The SX8636 will then boot up from the NVM and additional parameters from the host are not required anymore. In case the host desires to overwrite the boot-up NVM parameters (partly or even complete) this can be done by additional I2C communications. Revision 7_6, June 12 © 2012 Semtech Corp. 11 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.3 Scan Period The basic operation Scan period of the SX8636 sensing interface can be split into three periods over time. In the first period (Sensing) the SX8636 is sensing all enabled CAP inputs, from CAP0 towards CAP7. In the second period (Processing) the SX8636 processes the sensor data, verifies and updates the GPIO and I2C status registers. In the third period (Timer) the SX8636 is set in a low power mode and waits until a new cycle starts. Figure 7 shows the different SX8636 periods over time. Figure 7 Scan Period The scan period determines the minimum reaction time of the SX8636. 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 SX8636 generates the interrupt on the INTB pin. The shorter the scan period the faster the reaction time will be. Very low power consumption can be obtained by setting very long scan periods with the expense of having longer reaction times. Important: All external events like GPIO, I2C and INTB are updated in the processing period, so once every scan period. If e.g. a GPI would change state directly after the processing period then this will be reported with a delay of one scan period later in time. 3.4 Operation modes The SX8636 has 3 operation modes. The main difference is found in the reaction time (corresponding to the scan period) and power consumption. Active mode offers fast scan periods. The typical reaction time is 30ms. All enabled sensors are scanned and information data is processed within this interval. Doze mode increases the scan period time which increases the reaction time to 195ms typical and at the same time reduces the operating current. Sleep mode turns the SX8636 OFF, except for the I2C and GPI peripheral, minimizing operating current while maintaining the power supplies. In Sleep mode the SX8636 does not do any sensor scanning. The user can specify other scan periods for the Active and Doze mode and decide for other compromises between reaction time and power consumption. In 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 SX8636 is not used for a specific time it can go from Active mode into Doze mode and power will be saved. This time-out is determined by the Passive Timer which can be configured by the user or turned OFF if not required. Revision 7_6, June 12 © 2012 Semtech Corp. 12 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING To leave Doze mode and enter Active mode this can be done by a simple touch on any button. For some applications a single button touch might cause undesired wakening up and Active mode would be entered too often. The SX8636 offers therefore a smart wake-up sequence feature in which the user needs to touch and release a correct sequence of buttons before Active mode will be entered. This is explained in more detail in the Wake-Up Sequence section. The host can decide to force the operating mode by issuing commands over the I2C (using register CompOpMode) and take fully control of the SX8636. The diagram in Figure 8 shows the available operation modes and the possible transitions. Figure 8 Operation modes Revision 7_6, June 12 © 2012 Semtech Corp. 13 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.5 Sensors on the PCB The capacitive sensors are relatively simple copper areas on the PCB connected to the eight SX8636 capacitive sensor input pins (CAP0…CAP7).The sensors are covered by isolating overlay material (typically 1mm...3mm). The area of a sensor is typically one square centimeter which corresponds about to the area of a finger touching the overlay material. The capacitive sensors can be setup as ON/OFF buttons for either touch or proximity sensing (see example Figure 9). Figure 9 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 3.6.1 Button Information Button Information The touch buttons have two simple states (see Figure 10): ON (touched by finger) and OFF (released and no finger press). Figure 10 Buttons A finger is detected as soon as the number of ticks from the ASI reaches a user-defined threshold plus a hysteresis. A release is detected if the ticks from the ASI go below the threshold minus a hysteresis. The hysteresis around the threshold avoids rapid touch and release signaling 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. Revision 7_6, June 12 © 2012 Semtech Corp. 14 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.7 Analog Sensing Interface The Analog Sensing Interface (ASI) converts the charge on the sensors into ticks which will be further digitally processed. The 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 11). ASI cap0 cap1 analog multiplexor processing voltage reference switches cap2 ticks (raw) ticks-diff ADC low pass ticks-ave Offset compensation DAC cap7 compensation DCV Cint Figure 11 Analog Sensor Interface To get the ticks representing the charge on a specific sensor the ASI will execute several steps. The charge on a sensor 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 SX8636 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 (ie for touch buttons => finger not touching yet, for proximity sensors => finger/hand not close enough). Once the ASI has finished the first sensor, the ticks are stored and the ASI will start measuring the next sensor until all (enabled) sensors pins have been treated. In case some sensors are disabled then these result in lower power consumption simply because the ASI is active for a shorter period and the following processing period will be shorter. Revision 7_6, June 12 © 2012 Semtech Corp. 15 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING The ticks from the ASI will then be handled by the digital processing. 3.8 Offset Compensation The capacitance at the CAP pins is determined by an intrinsic capacitance of the integrated circuit, the PCB traces, 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 SX8636 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 SX8636 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 SX8636 is shut down the compensation values will be lost. At a next power-up the procedure starts all over again. This assures that the SX8636 will operate under any condition. Powering up at e.g. different temperatures will not change the performance of the SX8636 and the host does not have to do anything special. The DCVs do not need to be updated if the external conditions remain stable. However if e.g. temperature changes this will influence the external capacitance. The ADC ticks will drift then slowly around zero values basically because of the mismatch of the compensation circuitry and the external capacitance. In case the average value of the ticks become higher than the positive noise threshold (configurable by user) or lower than the negative threshold (configurable by user) then the SX8636 will initiate a compensation procedure and find a new set of DCVs. Compensation procedures can as well be initiated by the SX8636 on periodic intervals. Even if the ticks remain within the positive and negative noise thresholds the compensation procedure will then estimate new sets of DCVs. Finally the host can initiate a compensation procedure by using the I2C interface (in Active or Doze mode). This is e.g. required after the host changed the sensitivity of sensors. Revision 7_6, June 12 © 2012 Semtech Corp. 16 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.9 Processing The first processing step of the raw ticks, coming out of the ASI, is low pass filtering to obtain an estimation of the average capacitance: tick-ave (see Figure 12). This slowly varying average is important in the detection of slowly changing environmental changes. ASI processing SPM processing ticks (raw) tick-diff PWM LED controller tick-ave GPIO controller low pass I2C compensation DCV Figure 12 Processing The difference of the tick average and the raw ticks, tick-diff, is a good estimation of rapid changing input capacitances. The tick-diff, tick-ave and the configuration parameters in the SPM are then processed and determines the sensor information, I2C registers status and PWM control. 3.10 Configuration Figure 13 shows the building blocks used for configuring the SX8636. Figure 13 Configuration The default configuration parameters of the SX8636 are stored in the Quick Start Memory (QSM). This configuration data is setup to a very common application for the SX8636 with eight buttons. Without any programming or host interaction the SX8636 will startup in the Quick Start Application. Revision 7_6, June 12 © 2012 Semtech Corp. 17 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING The QSM settings are fixed and can not be changed by the user. In case the application needs different settings than the QSM settings then the SX8636 can be setup and/or programmed over the I2C interface. The configuration parameters of the SX8636 can be stored in the Multiple Time Programmable (MTP) Non Volatile Memory (NVM). The NVM contains all those parameters that are defined and stable for the application. Examples are the number of sensors enabled, sensitivity, active and Doze scan period. The details of these parameters are described in the next chapters. At power up the SX8636 checks if the NVM contains valid data. In that case the configuration parameter source becomes the NVM. If the NVM is empty or non-valid then the configuration source becomes the QSM. In the next step the SX8636 copies the configuration parameter source (QSM or NVM) into the Shadow Parameter Memory (SPM). The SX8636 is operational and uses the configuration parameters of the SPM. During power down or reset event the SPM loses all content. It will automatically be reloaded (from QSM or NVM) following power up or at the end of the reset event. The host will interface with the SX8636 through the I2C bus. The I2C of the SX8636 consists of 16 registers. Some of these I2C registers are used to read the status and information of the button. Other I2C registers allow the host to take control of the SX8636. The host can e.g. decide to change the operation mode from Active mode to Doze mode or go into Sleep (according to Figure 8). Two additional modes allow the host to have an access to the SPM or indirect access to the NVM. These modes are required during development, can be used in real time or in-field programming. Figure 14 shows the Host SPM mode. In this mode the host can decide to overwrite the SPM. This is useful during the development phases of the application where the configuration parameters are not yet fully defined and as well during the operation of the application if some parameters need to be changed dynamically. Figure 14 Host SPM mode The content of the SPM remains valid as long as the SX8636 is powered and no reset is performed. After a power down or reset the host needs to re-write the SPM if relevant for the application. Figure 15 shows the Host NVM mode. In this mode the host will be able to write the NVM. Revision 7_6, June 12 © 2012 Semtech Corp. 18 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Figure 15 Host NVM mode The writing of the host towards the NVM is not done directly but done in 2 steps (Figure 15). In the first step the host writes to the SPM (as in Figure 14). In the second step the host signals the SX8636 to copy the SPM content into the NVM. Initially the NVM memory is empty and it is required to determine a valid parameter set for the application. This can be done during the development phase using dedicated evaluation hardware representing the final application. This development phase uses probably initially the host SPM mode which allows faster iterations. Once the parameter set is determined this can be written to the NVM over the I2C using the 2 steps approach by the host or a dedicated programmer for large volumes production (as described in the paragraphs 6.6 and 6.7). 3.11 Power Management The SX8636 uses on-chip voltage regulators which are controlled by the on-chip microprocessor. The regulators need to be stabilized with an external capacitor between VANA and ground and between VDIG and ground (see Table 5). Both regulators are designed to only drive the SX8636 internal circuitry and must not be loaded externally. 3.12 Clock Circuitry The SX8636 has its own internal clock generation circuitry that does not require any external components. The clock circuitry is optimized for low power operation and is controlled by the on-chip microprocessor. The typical operating frequency of the oscillating core is 16.7MHz from which all other lower frequencies are derived. 3.13 I2C interface The I2C interface allows the communication between the host and the SX8636. The I2C slave implemented on the SX8636 is compliant with the standard (100kb/s) and fast mode (400kb/s) The default SX8636 I2C address equals 0b010 1011. A different I2C address can be programmed by the user in the NVM. Revision 7_6, June 12 © 2012 Semtech Corp. 19 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.14 Reset The reset can be performed by 3 sources: - power up, - RESETB pin, - software reset. 3.14.1 Power up During power up the INTB is kept low. Once the power up sequence is terminated the INTB is released autonomously. The SX8636 is then ready for operation. Figure 16 Power Up vs. INTB During the power on period the SX8636 stabilizes the internal regulators, RC clocks and the firmware initializes all registers. During the power up the SX8636 is not accessible and I2C communications are forbidden. As soon as the INTB rises the SX8636 will be ready for I2C communication. 3.14.2 RESETB When RESETB is driven low the SX8636 will reset and start the power up sequence as soon as RESETB is driven high or pulled high. In case the user does not require a hardware reset control pin then the RESETB pin can be connected to VDD. Figure 17 Hardware Reset Revision 7_6, June 12 © 2012 Semtech Corp. 20 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.14.3 Software Reset To perform a software reset the host needs to write 0xDE followed by 0x00 at the SoftReset register at address 0xB1. Figure 18 Software Reset Revision 7_6, June 12 © 2012 Semtech Corp. 21 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.15 Interrupt 3.15.1 Power up During power up the INTB is kept low. Once the power up sequence is terminated the INTB is released autonomously. The SX8636 is then ready for operation. Figure 19 Power Up vs. INTB During the power on period the SX8636 stabilizes the internal regulators, RC clocks and the firmware initializes all registers. During the power up the SX8636 is not accessible and I2C communications are forbidden. As soon as the INTB rises the SX8636 will be ready for I2C communication. 3.15.2 Assertion INTB is updated in Active or Doze mode once every scan period. The INTB will be asserted: at the following events: • if a Button event occurred (touch or release if enabled). I2C register CapStatLsb show the detailed status of the Buttons, • if a GPI edge occurred (rising or falling if enabled). I2C register GpiStat shows the detailed status of the GPI pins, • when actually entering Active or Doze mode either through automatic wakeup or via host request (may be delayed by 1 scan period). I2C register CompOpmode shows the current operation mode, • once compensation procedure is completed either through automatic trigger or via host request (may be delayed by 1 scan period), • once SPM write is effective (may be delayed by 1 scan period), • once NVM burn procedure is completed (may be delayed by 1 scan period), • during reset (power up, hardware RESETB, software reset). 3.15.3 Clearing INTB is updated in Active or Doze mode once every scan period. The clearing of the INTB is done as soon as the host performs a read to the IrqSrc I2C register or reset is completed. Revision 7_6, June 12 © 2012 Semtech Corp. 22 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.15.4 Example A typical example of the assertion and clearing of the INTB and the I2C communication is shown in Figure 20. Figure 20 Interrupt and I2C When a button is touched the SX8636 will assert the interrupt (1). The host will read the IrqSrc information over the I2C and this clears the interrupt (2). If the finger releases the button the interrupt will be asserted (3). The host reading the IrqSrc information will clear the interrupt (4). In case the host does not react to an interrupt this results in a missing touch. 3.16 General Purpose Input and Outputs 3.16.1 Introduction and Definitions The SX8636 offers eight General Purpose Input and Outputs (GPIO) pins which can be configured in any of these modes: - GPI (General Purpose Input) - GPP (General Purpose PWM) - GPO (General Purpose Output) Each of these modes is described in more details in the following sections. The polarity of the GPP and GPO pins is defined as in figure below, driving an LED as example. It has to be set accordingly in SPM parameter GpioPolarity. Figure 21 Polarity definition, (a) normal, (b) inverted Revision 7_6, June 12 © 2012 Semtech Corp. 23 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING The PWM blocks used in GPP and GPO modes are 8-bits based and clocked at 2MHz typ. hence offering 256 selectable pulse width values with a granularity of 128us typ. Figure 22 PWM definition, (a) small pulse width, (b) large pulse width 3.16.2 GPI GPIOs configured as GPI will operate as digital inputs with standard low and high logic levels. Optional pull-up/down and debounce can be enabled. Each GPI is individually edge programmable for INTB generation which will also exit Sleep/Doze mode if relevant. SPM/I2C parameters applicable in GPI mode are listed in table below. Please refer to the relevant SPM/I2C parameters sections for more details. SPM I2C GpioMode GpioPullUpDown GpioInterrupt GpioDebounce IrqSrc[4] GpiStat GPI X X X X X X Table 7 SPM/I2C Parameters Applicable in GPI Mode 3.16.3 GPP GPIOs configured as GPP will operate as PWM outputs directly controlled by the host. A typical application is LED dimming. Typical GPP operation is illustrated in figure below. Figure 23 LED control in GPP mode SPM/I2C parameters applicable in GPP mode are listed in table below. Please refer to the relevant SPM/I2C parameters sections for more details. Revision 7_6, June 12 © 2012 Semtech Corp. 24 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING SPM I2C GpioMode GpioOutPwrUp GpioPolarity GpioIntensityOn GpioIntensityOff GpioFunction GppPinId GppIntensity GPP X 1 X X 1 X 1 X X X 1 X 1 At power up, GppIntensity of each GPP pin is initialized with GpioIntensityOn or GpioIntensityOff depending on GpioOutPwrUp corresponding bits value. Table 8 SPM/I2C Parameters Applicable in GPP Mode 3.16.4 GPO GPIOs configured as GPO will operate as digital outputs which can generate both standard low/high logic levels and PWM low/high duty cycles levels. Typical application is LED ON/OFF control. Transitions between ON and OFF states can be triggered either automatically in Autolight mode or manually by the host. This is illustrated in figures below. Figure 24 LED Control in GPO mode, Autolight OFF Figure 25 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 26 GPO ON transition (LED fade in), normal polarity, (a) linear, (b) logarithmic Revision 7_6, June 12 © 2012 Semtech Corp. 25 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Figure 27 GPO ON transition (LED fade in), inverted polarity, (a) linear, (b) logarithmic The fading out (e.g. after a button is released) is identical to the fading in but an additional off delay can be added before the fading starts (Figure 28 and Figure 29). Figure 28 GPO OFF transition (LED fade out), normal polarity, (a) linear, (b) logarithmic Figure 29 GPO OFF transition (LED fade out), inverted polarity, (a) linear, (b) logarithmic Please note that standard high/low logic signals are just a specific case of GPO mode and can also be generated simply by setting inc/dec time to 0 (ie OFF) and programming intensity OFF/ON to 0x00 and 0xFF. Revision 7_6, June 12 © 2012 Semtech Corp. 26 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING SPM/I2C parameters applicable in GPO mode are listed in table below. SPM I2C 1 2 GpioMode GpioOutPwrUp GpioAutoligth GpioPolarity GpioIntensityOn GpioIntensityOff GpioFunction GpioIncFactor GpioDecFactor GpioIncTime GpioDecTime GpioOffDelay GpoCtrl GPO X 1 X X X X X X X X X X X 2 X Only if Autolight is OFF, else must be left to 0 (default value) Only if Autolight is OFF, else ignored Table 9 SPM/I2C Parameters Applicable in GPO Mode Revision 7_6, June 12 © 2012 Semtech Corp. 27 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.16.5 Intensity index vs PWM pulse width Tables below are used to convert all intensity indexes parameters GpioIntensityOff, GpioIntensityOn and GppIntensity but also to generate fading in GPO mode During fading in(out), the index is automatically incremented(decremented) at every Inc(Dec)Time x Inc(Dec)Factor until it reaches the programmed GpioIntensityOn(Off) value. Index 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Lin/Log 0/0 2/0 3/0 4/0 5/0 6/2 7/2 8/2 9/2 10/2 11/2 12/2 13/2 14/2 15/3 16/3 17/3 18/3 19/3 20/3 21/3 22/3 23/3 24/4 25/4 26/4 27/4 28/4 29/4 30/4 31/4 32/5 Index 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Lin/Log 33/5 34/5 35/5 36/5 37/5 38/6 39/6 40/6 41/6 42/6 43/7 44/7 45/7 46/7 47/7 48/8 49/8 50/8 51/8 52/9 53/9 54/9 55/9 56/10 57/10 58/10 59/10 60/11 61/11 62/11 63/12 64/12 Index 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 Lin/Log 65/12 66/13 67/13 68/13 69/14 70/14 71/14 72/15 73/15 74/15 75/16 76/16 77/16 78/17 79/17 80/18 81/18 82/19 83/19 84/20 85/20 86/21 87/21 88/22 89/22 90/23 91/23 92/24 93/24 94/25 95/25 96/26 Index 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 Lin/Log 97/26 98/27 99/27 100/28 101/29 102/29 103/30 104/30 105/31 106/32 107/32 108/33 109/33 110/34 111/35 112/35 113/36 114/37 115/38 116/38 117/39 118/40 119/40 120/41 121/42 122/43 123/44 124/44 125/45 126/46 127/47 128/48 Index 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 Lin/Log 129/48 130/49 131/50 132/51 133/52 134/53 135/54 136/55 137/55 138/56 139/57 140/58 141/59 142/60 143/61 144/62 145/63 146/64 147/65 148/66 149/67 150/68 151/69 152/71 153/72 154/73 155/74 156/75 157/76 158/77 159/78 160/80 Index 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 Lin/Log 161/81 162/82 163/83 164/84 165/86 166/87 167/88 168/89 169/91 170/92 171/93 172/95 173/96 174/97 175/99 176/100 177/101 178/103 179/104 180/106 181/107 182/109 183/110 184/111 185/113 186/114 187/116 188/117 189/119 190/121 191/122 192/124 Index 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 Lin/Log 193/125 194/127 195/129 196/130 197/132 198/133 199/135 200/137 201/139 202/140 203/142 204/144 205/146 206/147 207/149 208/151 209/153 210/155 211/156 212/158 213/160 214/162 215/164 216/166 217/168 218/170 219/172 220/174 221/176 222/178 223/180 224/182 Index 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 Lin/Log 225/184 226/186 227/188 228/190 229/192 230/194 231/197 232/199 233/201 234/203 235/205 236/208 237/210 238/212 239/215 240/217 241/219 242/221 243/224 244/226 245/229 246/231 247/233 248/236 249/238 250/241 251/243 252/246 253/248 254/251 255/253 256/256 Lin/Log 64/131 63/129 62/127 61/126 60/124 59/123 58/121 57/119 56/117 55/116 54/114 53/112 52/110 51/109 50/107 49/105 48/103 47/101 46/100 45/98 44/96 43/94 42/92 41/90 40/88 39/86 38/84 37/82 36/80 35/78 34/76 33/74 Index 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 Lin/Log 32/72 31/70 30/68 29/66 28/64 27/62 26/59 25/57 24/55 23/53 22/50 21/48 20/46 19/44 18/41 17/39 16/37 15/35 14/32 13/30 12/27 11/25 10/23 9/20 8/18 7/15 6/13 5/10 4/8 3/5 2/3 0/0 Table 10 Intensity index vs. PWM pulse width (normal polarity) Index 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Lin/Log 256/256 255/256 254/256 253/256 252/256 251/254 250/254 249/254 248/254 247/254 246/254 245/254 244/254 243/254 242/253 241/253 240/253 239/253 238/253 237/253 236/253 235/253 234/253 233/252 232/252 231/252 230/252 229/252 228/252 227/252 226/252 225/251 Index 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 Lin/Log 224/251 223/251 222/251 221/251 220/251 219/250 218/250 217/250 216/250 215/250 214/249 213/249 212/249 211/249 210/249 209/248 208/248 207/248 206/248 205/247 204/247 203/247 202/247 201/246 200/246 199/246 198/246 197/245 196/245 195/245 194/244 193/244 Index 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 Lin/Log 192/244 191/243 190/243 189/243 188/242 187/242 186/242 185/241 184/241 183/241 182/240 181/240 180/240 179/239 178/239 177/238 176/238 175/237 174/237 173/236 172/236 171/235 170/235 169/234 168/234 167/233 166/233 165/232 164/232 163/231 162/231 161/230 Index 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 Lin/Log 160/230 159/229 158/229 157/228 156/227 155/227 154/226 153/226 152/225 151/224 150/224 149/223 148/223 147/222 146/221 145/221 144/220 143/219 142/218 141/218 140/217 139/216 138/216 137/215 136/214 135/213 134/212 133/212 132/211 131/210 130/209 129/208 Index 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 Lin/Log 128/208 127/207 126/206 125/205 124/204 123/203 122/202 121/201 120/201 119/200 118/199 117/198 116/197 115/196 114/195 113/194 112/193 111/192 110/191 109/190 108/189 107/188 106/187 105/185 104/184 103/183 102/182 101/181 100/180 99/179 98/178 97/176 Index 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 Lin/Log 96/175 95/174 94/173 93/172 92/170 91/169 90/168 89/167 88/165 87/164 86/163 85/161 84/160 83/159 82/157 81/156 80/155 79/153 78/152 77/150 76/149 75/147 74/146 73/145 72/143 71/142 70/140 69/139 68/137 67/135 66/134 65/132 Index 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 Table 11 Intensity index vs. PWM pulse width (inverted polarity) Recommended/default settings are inverted polarity (to take advantage from high sink current capability) and logarithmic mode (due to the non-linear response of the human eye). Revision 7_6, June 12 © 2012 Semtech Corp. 28 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 3.17 Smart Wake Up The SX8636 offers a smart wake up mechanism (up to 6 keys) which allows waking-up from the Doze low power mode to the Active mode in a secure/controlled way and not by any unintentional sensor activation. Until the full correct wake-up sequence is entered, the SX8636 will remain in Doze mode. Any wrong key implies the whole sequence to be entered again. Please note that each key touch must be followed by a release to be validated. Hence if a proximity sensor and a touch button part of the wake-up sequence are interleaved on the PCB (ie if you cannot touch the button without triggering proximity detection) the smart wake up feature cannot be used since the proximity sensor is not “released” before the buttons are touched. In this case the smart wakeup sequence must be turned OFF. The smart wake-up mechanism can also be disabled which implies that Doze mode can hence only be exited from GPI or I2C command. Revision 7_6, June 12 © 2012 Semtech Corp. 29 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 4 PIN DESCRIPTIONS 4.1 Introduction This chapter describes briefly the pins of the SX8636, the way the pins are protected, if the pins are analog, digital, require pull up or pull down resistors and show control signals if these are available. 4.2 ASI pins CAP0, CAP1, ..., CAP7 The capacitance sensor pins (CAP0, CAP1, ..., CAP7) are connected directly to the ASI circuitry which converts the sensed capacitance into digital values. The capacitance sensor pins which are not used should be left open. The enabled CAP pins need be connected directly to the sensors without significant resistance (typical below some ohms, connection vias are allowed). The capacitance sensor pins are protected to VANA and GROUND. Figure 30 shows the simplified diagram of the CAP0, CAP1, ..., CAP7 pins. SX8636 VANA sensor CAPx CAP_INx ASI Note : x = 0, 1,2,…7 Figure 30 Simplified diagram 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 SX8636. The CN and CP are protected to VANA and GROUND. Figure 31 shows the simplified diagram of the CN and CP pins. Revision 7_6, June 12 © 2012 Semtech Corp. 30 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING SX8636 VANA CP ASI VANA CN Figure 31 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 32 shows a simplified diagram of the INTB pin. VDD SX8636 R_INT INTB to host INT Figure 32 Simplified diagram of INTB Revision 7_6, June 12 © 2012 Semtech Corp. 31 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 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 33 shows the simplified diagram of the SCL pin. VDD SX8636 R_SCL SCL SCL_IN from host Figure 33 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 34 shows the simplified diagram of the SDA pin. VDD SX8636 R_SDA SDA SDA_IN from/to host SDA_OUT Figure 34 Simplified diagram of SDA Revision 7_6, June 12 © 2012 Semtech Corp. 32 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING RESETB The RESETB pin is a high impedance input pin. The RESETB pin is protected to VDD using dedicated devices. The RESETB pin has diode protected to GROUND. Figure 35 shows the simplified diagram of the RESETB pin controlled by the host. VDD SX8636 R_RESETB RESETB RESETB_IN from host Figure 35 Simplified diagram of RESETB controlled by host Figure 36 shows the RESETB without host control. VDD SX8636 RESETB RESETB_IN Figure 36 Simplified diagram of RESETB without host control Revision 7_6, June 12 © 2012 Semtech Corp. 33 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 4.4 Power management pins The power management pins consist of the Power, Ground and Regulator pins. VDD VDD is a power pin and is the main power supply for the SX8636. VDD has protection to GROUND. Figure 37 shows a simplified diagram of the VDD pin. SX8636 VDD VDD Figure 37 Simplified diagram of VDD GND The SX8636 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 38 shows a simplified diagram of the GND pin. SX8636 VDD GND GND Figure 38 Simplified diagram of GND Revision 7_6, June 12 © 2012 Semtech Corp. 34 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING VANA, VDIG The SX8636 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 39 shows a simplified diagram of the VANA and VDIG pin. SX8636 VDD VDIG VDIG Cvdig GND VDD VANA VANA Cvana GND Figure 39 Simplified diagram of VANA and VDIG 4.5 General purpose IO pins The SX8636 has 8 General purpose input/output (GPIO) pins. All the GPIO pins have protection to VDD and GND. The GPIO pins can be configured as GPI, GPO or GPP. Figure 40 shows a simplified diagram of the GPIO pins. Figure 40 Simplified diagram of GPIO pins Revision 7_6, June 12 © 2012 Semtech Corp. 35 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 5 DETAILED CONFIGURATION DESCRIPTIONS 5.1 Introduction The SX8636 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 SX8636. . The SPM is split by functionality into 5 configuration sections: • General section: operating modes, • Capacitive Sensors section: related to lower level capacitive sensing, • Button: related to the conversion from sensor data towards button information, • Mapping: related to mapping of button information towards wake-up and GPIO pins, • GPIO: related to the setup of the GPIO pins. The total address space of the SPM and the NVM is 128 bytes, from address 0x00 to address 0x7F. Two types of memory addresses, data are accessible to the user. • ‘application data’: Application dependent data that need to be configured by the user. • ‘reserved’: Data that need to be maintained by the user to the QSM default values (i.e. when NVM is burned). The Table 12 and Table 13 resume the complete SPM address space and show the ‘application data’ and ‘reserved’ addresses, the functional split and the default values (loaded from the QSM). Revision 7_6, June 12 © 2012 Semtech Corp. 36 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Name default QSM value Address Name 0x00 Reserved 0xxx 0x20 Reserved 0x01 Reserved 0xxx 0x21 BtnCfg 0x30 0x02 Reserved 0x21 0x22 BtnAvgThresh 0x50 0x03 Reserved 0xxx 0x23 BtnCompNegThresh 0x50 I2CAddress 0x2B 0x24 BtnCompNegCntMax 0x01 ActiveScanPeriod 0x02 0x25 BtnHysteresis 0x0A DozeScanPeriod 0x0D 0x26 BtnStuckAtTimeout 0x00 PassiveTimer 0x00 0x27 Reserved 0x00 0x00 0x28 Reserved 0x00 0x05 0x06 General 0x04 0x07 0x08 Reserved Button Address default QSM value 0x00 0x09 CapModeMisc 0x01 0x29 Reserved 0x00 0x0A Reserved 0x00 0x2A Reserved 0xFF 0x0B CapMode7_4 0x55 0x2B Reserved 0x00 0x0C CapMode3_0 0x55 0x2C Reserved 0x00 0x0D CapSensitivity0_1 0x00 0x2D Reserved 0x00 0x0E CapSensitivity2_3 0x00 0x2E Reserved 0x00 0x0F CapSensitivity4_5 0x00 0x2F Reserved 0x00 CapSensitivity6_7 0x00 0x30 Reserved 0x00 0x11 Reserved 0x00 0x31 Reserved 0x00 Reserved 0x00 0x32 Reserved CapThresh0 0xA0 0x33 MapWakeupSize 0x00 CapThresh1 0xA0 0x34 MapWakeupValue0 0x00 CapThresh2 0xA0 0x35 MapWakeupValue1 0x00 0x12 0x13 0x14 0x15 Capacitive Sensors 0x10 0x00 0xA0 0x36 MapWakeupValue2 0x00 CapThresh4 0xA0 0x37 MapAutoLight0 0x76 0x18 CapThresh5 0xA0 0x38 MapAutoLight1 0x54 0x19 CapThresh6 0xA0 0x39 MapAutoLight2 0x32 0x1A CapThresh7 0xA0 0x3A MapAutoLight3 0x10 0x1B Reserved 0xA0 0x3B MapAutoLightGrp0Msb 0x00 0x1C Reserved 0xA0 0x3C MapAutoLightGrp0Lsb 0x00 0x1D Reserved 0xA0 0x3D MapAutoLightGrp1Msb 0x00 0x1E Reserved 0xA0 0x3E MapAutoLightGrp1Lsb 0x00 0x1F CapPerComp 0x00 0x3F Mapping CapThresh3 0x17 0x16 Reserved 0x00 Table 12 SPM address map: 0x00…0x3F Note • ‘0xxx’: write protected data Revision 7_6, June 12 © 2012 Semtech Corp. 37 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Address Name default QSM value Address Name default QSM value 0x00 0x60 GpioDecTime1_0 0x44 0x41 GpioMode3_0 0x00 0x61 GpioOffDelay7_6 0x00 0x42 GpioOutPwrUp 0x00 0x62 GpioOffDelay5_4 0x00 0x43 GpioAutoLight 0xFF 0x63 GpioOffDelay3_2 0x00 0x44 GpioPolarity 0x00 0x64 GpioOffDelay1_0 0x00 0x45 GpioIntensityOn0 0xFF 0x65 GpioPullUpDown7_4 0x00 0x46 GpioIntensityOn1 0xFF 0x66 GpioPullUpDown3_0 0x00 0x47 GpioIntensityOn2 0xFF 0x67 GpioInterrupt7_4 0x00 0x48 GpioIntensityOn3 0xFF 0x68 GpioInterrupt3_0 0x00 0x49 GpioIntensityOn4 0xFF 0x69 GpioDebounce 0x00 0x4A GpioIntensityOn5 0xFF 0x6A Reserved 0x00 0x4B GpioIntensityOn6 0xFF 0x6B Reserved 0x00 0x4C GpioIntensityOn7 0xFF 0x6C Reserved 0x00 0x4D GpioIntensityOff0 0x00 0x6D Reserved 0x00 0x4E GpioIntensityOff1 0x00 0x6E Reserved 0x00 0x4F GpioIntensityOff2 0x00 0x6F Reserved 0x50 GpioIntensityOff3 0x00 0x70 CapProxEnable 0x46 0x51 GpioIntensityOff4 0x00 0x71 Reserved 0x10 0x52 GpioIntensityOff5 0x00 0x72 Reserved 0x45 0x53 GpioIntensityOff6 0x00 0x73 Reserved 0x02 0x54 GpioIntensityOff7 0x00 0x74 Reserved 0xFF 0x55 Reserved 0xFF 0x75 Reserved 0xFF 0x56 GpioFunction 0x00 0x76 Reserved 0xFF 0x57 GpioIncFactor 0x00 0x77 Reserved 0xD5 0x58 GpioDecFactor 0x00 0x78 Reserved 0x55 0x59 GpioIncTime7_6 0x00 0x79 Reserved 0x55 0x5A GpioIncTime5_4 0x00 0x7A Reserved 0x7F 0x5B GpioIncTime3_2 0x00 0x7B Reserved 0x23 0x5C GpioIncTime1_0 0x00 0x7C Reserved 0x22 0x5D GpioDecTime7_6 0x44 0x7D Reserved 0x41 0x50 Gpio GpioMode7_4 Gpio 0x40 0x5E GpioDecTime5_4 0x44 0x7E Reserved 0xFF 0x5F GpioDecTime3_2 0x44 0x7F SpmCrc* 0xD0 Table 13 SPM address map: 0x40…0x7F Note* • SpmCrc: Revision 7_6, June 12 CRC depending on SPM content, updated in Active or Doze mode. © 2012 Semtech Corp. 38 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 5.2 General Parameters General Parameters Address Name Bits Description 0x04 I2CAddress 7 Reserved 6:0 Defines the I2C address (default 0x2B). The I2C address will be active after a reset. 0x05 ActiveScanPeriod 7:0 Active Mode Scan Period (Figure 7) 0x00: Reserved 0x01: 15ms 0x02: 30ms (default) … 0xFF: 255 x 15ms 0x06 DozeScanPeriod 7:0 Doze Mode Scan Period (Figure 7) 0x00: Reserved 0x01: 15ms … 0x0D: 195ms (default) … 0xFF: 255 x 15ms 0x07 PassiveTimer 7:0 Passive Timer on Button Information (Figure 8) 0x00: OFF (default) 0x01: 1 second … 0xFF: 255 seconds Table 14 General Parameters Revision 7_6, June 12 © 2012 Semtech Corp. 39 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 5.3 Capacitive Sensors Parameters Capacitive Sensors Parameters Address Name Bits Description 0x09 CapModeMisc 7:3 Reserved 2:0 IndividualSensitivity Defines common sensitivity for all sensors or individual sensor sensitivity. 001: Common settings (CapSensitivity0_1[7:4]) 100: Individual CAP sensitivity settings (CapSensitivityx_x) Else : Reserved 0x0A Reserved 7:0 Reserved 0x0B CapMode7_4 7:6 CAP7 Mode 5:4 CAP6 Mode 3:2 CAP5 Mode 1:0 CAP4 Mode 7:6 CAP3 Mode Button 5:4 CAP2 Mode Button 3:2 CAP1 Mode Button 1:0 CAP0 Mode Button 7:4 7:4 CAP0 Sensitivity - Common Sensitivity Defines the sensitivity. 0x0: Minimum (default) CAP1 Sensitivity 0x7: Maximum 0x8…0xF: Reserved CAP2 Sensitivity 3:0 CAP3 Sensitivity 7:4 CAP4 Sensitivity 3:0 CAP5 Sensitivity 7:4 CAP6 Sensitivity 3:0 CAP7 Sensitivity 0x0C 0x0D CapMode3_0 CapSensitivity0_1 3:0 0x0E 0x0F 0x10 CapSensitivity2_3 CapSensitivity4_5 CapSensitivity6_7 0x11 Reserved 7:0 Reserved 0x12 Reserved 7:0 Reserved 0x13 CapThresh0 7:0 CAP0 Touch Threshold 0x14 CapThresh1 7:0 CAP1 Touch Threshold 0x15 CapThresh2 7:0 CAP2 Touch Threshold 0x16 CapThresh3 7:0 CAP3 Touch Threshold 0x17 CapThresh4 7:0 CAP4 Touch Threshold 0x18 CapThresh5 7:0 CAP5 Touch Threshold 0x19 CapThresh6 7:0 CAP6 Touch Threshold 0x1A CapThresh7 7:0 CAP7 Touch Threshold 0x1B Reserved 7:0 Reserved 0x1C Reserved 7:0 Reserved 0x1D Reserved 7:0 Reserved 0x1E Reserved 7:0 Reserved Revision 7_6, June 12 © 2012 Semtech Corp. 40 Defines the mode of the CAP pin. 00: Disabled 01: Button 10: Reserved 11: Reserved Default Button Button Button Button Defines the Touch Threshold ticks. 0x00: 0, 0x01: 4, … 0xA0: 640 (default), … 0xFF: 1020 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Capacitive Sensors Parameters Address Name Bits Description 0x1F CapPerComp 7:4 Reserved 3:0 Periodic Offset Compensation 7:0 Enables proximity sensing: 0x46: OFF 0x74: ON 0x70 CapProxEnable Defines the periodic offset compensation. 0x0: OFF (default) 0x1: 1 second 0x2: 2 seconds … 0x7: 7 seconds 0x8: 16 seconds 0x9: 18 seconds … 0xE: 28 seconds 0xF: 60 seconds Table 15 Capacitive Sensors Parameters CapModeMisc By default the ASI is using a common sensitivity for all capacitive sensors as in the usual case overlay material and sensors sizes are about equal. The register bits CapSensitivity0_1[7:4] determine the sensitivity for all sensors in common sensitivity mode. It might be required to have a different, individual, sensitivity for each CAP pin (for example proximity sensor set to max sensitivity while touch sensors are set to a lower one). This can be obtained by setting CapModeMisc[2:0] to “100” The individual sensitivity mode results in longer sensing periods than required in common sensitivity mode. CapMode7_4, CapMode3_0: The CAP pins can be set as a button or disabled depending on the application. buttons minimum default maximum one eight eight Table 16 Possible CAP pin modes Buttons and disabled CAP pins can be attributed freely (examples in Figure 41). All buttons can be used for touch or proximity sensing, in the latter case register CapProxEnable needs to be set accordingly. Revision 7_6, June 12 © 2012 Semtech Corp. 41 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Figure 41 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 17. Sensitivity Approximate Maximum Tick Level (CapProxEnable = OFF) Approximate Maximum Tick Level (CapProxEnable = ON) 0 1000 4000 1 2000 8000 2 3000 12000 3 4000 16000 4 5000 20000 5 6000 24000 6 7000 28000 7 8000 32000 Table 17 ASI Maximum Tick Levels Revision 7_6, June 12 © 2012 Semtech Corp. 42 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING CapThresh0, CapThresh1, CapThresh2, CapThresh3, CapThresh4, CapThresh5, CapThresh6, CapThresh7: For each CAP pin a threshold level can be set individually. The threshold levels are used by the SX8636 for making touch and release decisions on e.g. touch or notouch. The details are explained in the sections for buttons. CapPerComp: The SX8636 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. Revision 7_6, June 12 © 2012 Semtech Corp. 43 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 5.4 Button Parameters Button Parameters Address Name Bits Description 0x21 BtnCfg 7:6 Defines the buttons events reporting method. 00: Multiple reporting of all touches and releases (default) 01: Single reporting of the first button touch. Next button touches and releases are ignored until release of the first button. 10: Reserved 11: Reserved 5:4 Defines the buttons interrupt (for all buttons) 00 : Interrupts masked 01 : Triggered on Touch 10 : Triggered on Release 11 : Triggered on Touch and Release (default) 3:2 Defines the number of samples at the scan period for determining a release 00: OFF, use incoming sample (default) 01: 2 samples debounce 10: 3 samples debounce 11: 4 samples debounce 1:0 Defines the number of samples at the scan period for determining a touch 00: OFF, use incoming sample (default) 01: 2 samples debounce 10: 3 samples debounce 11: 4 samples debounce 0x22 BtnAvgThresh 7:0 Defines the positive threshold for disabling the processing filter averaging. If ticks are above the threshold, then the averaging is suspended 0x00: 0 0x01: 4 … 0x50: 320 (default) … 0xFF: 1020 0x23 BtnCompNegThresh 7:0 Defines the negative offset compensation threshold. 0x00: 0 0x01: 4 … 0x50: 320 (default) … 0xFF: 1020 0x24 BtnCompNegCntMax 7:0 Defines the number of ticks (below the negative offset compensation threshold) which will initiate an offset compensation. 0x00: Reserved 0x01: 1 sample (default) … 0xFF-> samples 0x25 BtnHysteresis 7:0 Defines the button hysteresis corresponding to a percentage of the CAP thresholds (defined in Table 18). 0x00: 0% … 0x0A: 10% (default) … 0x64: 100% All buttons use the same hysteresis 0x26 BtnStuckAtTimeout 7:0 Defines the stuck at timeout. 0x00: OFF (default) Revision 7_6, June 12 © 2012 Semtech Corp. 44 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Button Parameters Address Name Bits Description 0x01: 1 second … 0xFF: 255 seconds Table 18 Button Configuration Parameters Please note that proximity sensors are configured as buttons and operate exactly the same way as touch buttons. All the parameters and procedures described below apply similarly. ticks_diff A reliable button operation requires a coherent setting of the registers. Figure 42 shows an example of a touch and a release. The ticks will vary slightly around the zero idle state. When the touch occurs the ticks will rise sharply. At the release of the button the ticks will go down rapidly and converge to the idle zero value. Figure 42 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 42 the touch is validated after 2 samples (BtnCfg [1:0] = 01). The release is detected immediately (BtnCfg [3:2] = 00) at the first sample which is below the threshold minus the hysteresis. BtnCfg The SX8636 can report all touches of multiple fingers or the SX8636 can be set to report only the first detected touch. In the later case all succeeding touches are ignored. The very first touch should be released before a next touch will be detected. The user can select to have the interrupt signal on touching a button, releasing a button or both In noisy environments it may be required to debounce the touch and release detection decision. In case the debounce is enabled the SX8636 will count up to the number of debounce samples BtnCfg [1:0], BtnCfg [3:2] before taking a touch or release decision. The sample period is identical to the scan period. BtnAvgThresh Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value. Revision 7_6, June 12 © 2012 Semtech Corp. 45 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING In case the ticks get slightly positive this is considered as normal operation. Very large positive tick values indicate a valid touch. The averaging filter is disabled as soon as the average reaches the value defined by BtnAvgThresh. This mechanism avoids that a valid touch will be averaged and finally the tick difference becomes zero. In case three or more sensors reach the BtnAvgThresh value simultaneously then the SX8636 will start an offset compensation procedure. ticks_diff Small environmental and system noise cause the ticks to vary slowly around the zero idle mode value. In case the ticks get slightly negative this is considered as normal operation. However large negative values will trigger an offset compensation phase and a new set of DCVs will be obtained. The decision to trigger a compensation phase based on negative ticks is determined by the value in the register BtnCompNegThresh and by the number of ticks below the negative thresholds defined in register BtnCompNegCntMax. An example is shown in Figure 43. Figure 43 Negative Ticks Offset Compensation Trigger BtnCompNegThresh Small negative ticks are considered as normal operation and will occur very often. Larger negative ticks however need to be avoided and a convenient method is to trigger an offset compensation phase. The new set of DCV will assure the idle ticks will be close to zero again. A trade-off has to be found for the value of this register. A negative threshold too close to zero will trigger a compensation phase very often. A very negative threshold will never trigger. BtnCompNegCntMax As soon as the ticks get smaller than the Negative Threshold the Negative Counter starts to count. If the counter goes beyond the Negative Counter Max then the offset compensation phase is triggered. The recommended value for this register is ‘1’ which means that the offset compensation starts on the first tick below the negative threshold. BtnHysteresis The hysteresis percentage is identical for all buttons. A touch is detected if the ticks are getting larger as the value defined by: CapThreshold + CapThreshold * hysteresis. A release is detected if the ticks are getting smaller as the value defined by: CapThreshold - CapThreshold * hysteresis. BtnStuckAtTimeout The stuckat timer can avoid sticky buttons. Revision 7_6, June 12 © 2012 Semtech Corp. 46 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING If the stuckat timer is set to one second then the touch of a finger will last only for one second and then a compensation will be performed and button hence considered released, even if the finger remains on the button 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. Revision 7_6, June 12 © 2012 Semtech Corp. 47 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 5.5 Mapping Parameters Mapping Parameters Address Name Bits Description 0x33 MapWakeupSize 7:3 Reserved 2:0 Doze -> Active wake up sequence size. 0: Any sensor event (default) 1: key0 2: key0, key1 … 6: key0, key1,…key5 7: No sensor event, only GPI or I2C cmd can exit Doze mode Each key must be followed by a release to be validated. Any other sensor event before the release is ignored. Any wrong key implies the whole sequence to be entered again. 0x34 0x35 0x36 0x37 0x38 0x39 0x3A MapWakeupValue0 MapWakeupValue1 MapWakeupValue2 MapAutoLight0 MapAutoLight1 MapAutoLight2 MapAutoLight3 7:4 key5 3:0 key4 7:4 key3 3:0 key2 7:4 key1 3:0 key0 7:4 GPIO[7] 3:0 GPIO[6] 7:4 GPIO[5] 3:0 GPIO[4] 7:4 GPIO[3] 3:0 GPIO[2] 7:4 GPIO[1] 3:0 GPIO[0] 0x3B MapAutoLightGrp0Msb 7:0 Reserved 0x3C MapAutoLightGrp0Lsb 7 Btn7 6 Btn6 5 Btn5 4 Btn4 3 Btn3 2 Btn2 1 Btn1 0 Btn0 0x3D MapAutoLightGrp1Msb 7:0 Reserved 0x3E MapAutoLightGrp1Lsb 7 Btn7 6 Btn6 5 Btn5 Revision 7_6, June 12 © 2012 Semtech Corp. 48 Defines the sensor event associated to each key. 0x00: Btn0 (default) 0x01: Btn1 … 0x07: Btn7 0x08…0x0F: Reserved Defines the mapping between GPOs (with Autolight ON) and sensor events. 0x00: Btn0 (default) 0x01: Btn1 … 0x07: Btn7 0x08…0x0B: Reserved 0x0C: Group0 as defined by MapAutoLightGrp0 0x0D: Group1 as defined by MapAutoLightGrp1 0x0E: Reserved 0x0F: Reserved Several GPOs can be mapped to the same sensor event and will be controlled simultaneously. Defines Group0 sensor events: 0: OFF (default) 1: ON If any of the enabled sensor events occurs the Group0 event will occur as well. All sensors events within the group can be independently set. Defines Group1 sensor events: 0: OFF (default) 1: ON www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Mapping Parameters Address Name Bits Description 4 Btn4 3 Btn3 2 Btn2 1 Btn1 0 Btn0 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. Table 19 Mapping Parameters MapWakeupSize The number of keys defining the wakeup sequence can be set from 1 to 6. If the size is set to 0 then wakeup is done on any sensor event. if the size is set to 6 then wakeup is done only by GPI or an I2C command (may be required if proximity sensing is enable, see §3.17 for more details). MapWakeupValue0, MapWakeupValue1, MapWakeupValue2 For the wakeup sequence Btn2 -> Btn5 -> Btn6 ->Btn0 the required register settings are: - MapWakeupSize set to 0x04, - key0 = 0x2 - key1 = 0x5 => MapWakeupValue2 set to 0x52 - key2 = 0x6 - key3 = 0x0 => MapWakeupValue2 set to 0x06 MapAutoLight0, MapAutoLight1, MapAutoLight2, MapAutoLight3 MapAutoLightGrp0Msb, MapAutoLightGrp0Lsb, MapAutoLightGrp1Msb, MapAutoLightGrp1Lsb These registers define the mapping between the GPO pins (with Autolight ON) and the sensor information which will control its ON/OFF state. The mapping can be done to a specific sensor event but also on groups (in this case any sensor event in the group will control the GPO). Table 20 defines for each selectable sensor event, which action will trigger corresponding GPO to switch ON or OFF. MapAutoLight BtnX GPO ON GPO OFF Touch Release Table 20 Autolight Mapping, Sensor Information Examples: - If GPO[0] should change state accordingly to Btn4 then MapAutoLight3[3:0] should be set to 0x04. - If GPO[0] should change state accordingly to Btn0 or Btn1 then Group0 can be used as following: - MapAutoLight3[3:0] should be set to 0x0C (ie Group0). - MapAutoLightGrp0 should be set to 0x0003 (ie Btn0 or Btn1) Revision 7_6, June 12 © 2012 Semtech Corp. 49 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 5.6 GPIO Parameters GPIO Parameters Address Name Bits Description 0x40 GpioMode7_4 7:6 GPIO[7] Mode 5:4 GPIO[6] Mode 3:2 GPIO[5] Mode Defines the GPIO mode. 00: GPO (default) 01: GPP 10: GPI 11: Reserved 1:0 GPIO[4] Mode 0x41 GpioMode3_0 7:6 GPIO[3] Mode 5:4 GPIO[2] Mode 3:2 GPIO[1] Mode 1:0 GPIO[0] Mode 0x42 GpioOutPwrUp 7:0 GPIO[7] Output Value at Power Up GPIO[6] Output Value at Power Up GPIO[5] Output Value at Power Up GPIO[4] Output Value at Power Up GPIO[3] Output Value at Power Up GPIO[2] Output Value at Power Up GPIO[1] Output Value at Power Up GPIO[0] Output Value at Power Up 0x43 GpioAutoLight 7:0 GPIO[7] AutoLight GPIO[6] AutoLight Defines the values of GPO and GPP pins after power up ie default values of I2C parameters GpoCtrl and GppIntensity respectively. 0: OFF(GPO) / IntensityOff (GPP) (default) 1: ON (GPO) / IntensityOn (GPP) Bits corresponding to GPO pins with Autolight ON should be left to 0. Before being actually initialized GPIOs are set as inputs with pull up. Enables Autolight in GPO mode 0 : OFF 1 : ON (default) GPIO[5] AutoLight GPIO[4] AutoLight GPIO[3] AutoLight GPIO[2] AutoLight GPIO[1] AutoLight GPIO[0] AutoLight 0x44 GpioPolarity 7:0 GPIO[7] Output Polarity GPIO[6] Output Polarity GPIO[5] Output Polarity Defines the polarity of the GPO and GPP pins. 0: Inverted (default) 1: Normal GPIO[4] Output Polarity GPIO[3] Output Polarity GPIO[2] Output Polarity GPIO[1] Output Polarity GPIO[0] Output Polarity 0x45 GpioIntensityOn0 0x46 GpioIntensityOn1 0x47 GpioIntensityOn2 Revision 7_6, June 12 7:0 ON Intensity Index © 2012 Semtech Corp. 50 Defines the ON intensity index 0x00: 0 0x01: 1 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING GPIO Parameters Address Name 0x48 GpioIntensityOn3 0x49 GpioIntensityOn4 0x4A GpioIntensityOn5 0x4B GpioIntensityOn6 0x4C GpioIntensityOn7 0x4D GpioIntensityOff0 0x4E GpioIntensityOff1 0x4F GpioIntensityOff2 0x50 GpioIntensityOff3 0x51 GpioIntensityOff4 0x52 GpioIntensityOff5 0x53 GpioIntensityOff6 0x54 GpioIntensityOff7 0x56 GpioFunction Bits Description … 0xFF: 255 (default) 7:0 OFF Intensity Index Defines the OFF intensity index 0x00: 0 (default) 0x01: 1 … 0xFF: 255 7:0 GPIO[7] Function Defines the intensity index vs PWM pulse width function. 0: Logarithmic (default) 1: Linear GPIO[6] Function GPIO[5] Function GPIO[4] Function GPIO[3] Function GPIO[2] Function GPIO[1] Function GPIO[0] Function 0x57 GpioIncFactor 7:0 GPIO[7] Fading Increment Factor GPIO[6] Fading Increment Factor GPIO[5] Fading Increment Factor Defines the fading increment factor. 0: 1, intensity index incremented every increment time (default) 1: 16, intensity index incremented every 16 increment times GPIO[4] Fading Increment Factor GPIO[3] Fading Increment Factor GPIO[2] Fading Increment Factor GPIO[1] Fading Increment Factor GPIO[0] Fading Increment Factor 0x58 GpioDecFactor 7:0 GPIO[7] Fading Decrement Factor GPIO[6] Fading Decrement Factor GPIO[5] Fading Decrement Factor Defines the fading decrement factor. 0: 1, intensity index decremented every decrement time (default) 1: 16, intensity index decremented every 16 decrement times GPIO[4] Fading Decrement Factor GPIO[3] Fading Decrement Factor GPIO[2] Fading Decrement Factor GPIO[1] Fading Decrement Factor GPIO[0] Fading Decrement Factor 0x59 GpioIncTime7_6 Revision 7_6, June 12 7:4 GPIO[7] Fading Increment Time © 2012 Semtech Corp. 51 Defines the fading increment time. www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING GPIO Parameters Address Name Bits Description 3:0 GPIO[6] Fading Increment Time 0x5A GpioIncTime5_4 7:4 GPIO[5] Fading Increment Time 3:0 GPIO[4] Fading Increment Time 0x5B GpioIncTime3_2 7:4 GPIO[3] Fading Increment Time 3:0 GPIO[2] Fading Increment Time 0x5C GpioIncTime1_0 0x0: OFF (default) 0x1: 0.5ms 0x2: 1ms … 0xF: 7.5ms 7:4 GPIO[1] Fading Increment Time The total fading in time will be: GpioIncTime*GpioIncFactor* (GpioIntensityOn – GpioIntensityOff) 3:0 GPIO[0] Fading Increment Time 0x5D GpioDecTime7_6 7:4 GPIO[7] Fading Decrement Time 3:0 GPIO[6] Fading Decrement Time 0x5E GpioDecTime5_4 7:4 GPIO[5] Fading Decrement Time 3:0 GPIO[4] Fading Decrement Time 0x5F GpioDecTime3_2 7:4 GPIO[3] Fading Decrement Time 3:0 GPIO[2] Fading Decrement Time 0x60 GpioDecTime1_0 7:4 GPIO[1] Fading Decrement Time 3:0 GPIO[0] Fading Decrement Time 0x61 GpioOffDelay7_6 7:4 GPIO[7] OFF Delay 3:0 GPIO[6] OFF Delay 0x62 GpioOffDelay5_4 7:4 GPIO[5] OFF Delay 3:0 GPIO[4] OFF Delay 0x63 GpioOffDelay3_2 7:4 GPIO[3] OFF Delay Defines the fading decrement time. 0x0: OFF 0x1: 0.5ms 0x2: 1ms … 0x4: 2.0ms (default) … 0xF: 7.5ms The total fading out time will be: GpioDecTime*GpioDecFactor* (GpioIntensityOn – GpioIntensityOff) Defines the delay after GPO OFF trigger before fading out starts. 0x0: OFF (default) 0x1: 200ms 0x2: 400ms … 0xF: 3000ms 3:0 GPIO[2] OFF Delay 0x64 GpioOffDelay1_0 7:4 GPIO[1] OFF Delay 3:0 GPIO[0] OFF Delay 0x65 GpioPullUpDown7_4 7:6 GPIO[7] Pullup/down 5:4 GPIO[6] Pullup/down 3:2 GPIO[5] Pullup/down Enables pullup/down resistors for GPI pins. 00 : None (default) 01 : Pullup 10 : Pulldown 11 : Reserved 1:0 GPIO[4] Pullup/down 0x66 GpioPullUpDown3_0 7:6 GPIO[3] Pullup/down 5:4 GPIO[2] Pullup/down 3:2 GPIO[1] Pullup/down 1:0 GPIO[0] Pullup/down 0x67 GpioInterrupt7_4 7:6 GPI[7] Interrupt 5:4 GPI[6] Interrupt 3:2 GPI[5] Interrupt 1:0 GPI[4] Interrupt 0x68 GpioInterrupt3_0 7:6 GPI[3] Interrupt Defines the GPI edge which will trigger INTB falling edge and exit Sleep/Doze modes if relevant. 00 : None (default) 01 : Rising 10 : Falling 11 : Both 5:4 GPI[2] Interrupt 3:2 GPI[1] Interrupt Revision 7_6, June 12 © 2012 Semtech Corp. 52 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING GPIO Parameters Address Name Bits Description 1:0 GPI[0] Interrupt 0x69 GpioDebounce 7:0 GPI[7] Debounce Enables the GPI debounce (done on 10 consecutive samples at 1ms). 0 : OFF (default) 1 : ON GPI[6] Debounce GPI[5] Debounce GPI[4] Debounce GPI[3] Debounce GPI[2] Debounce GPI[1] Debounce GPI[0] Debounce Table 21 GPIO Parameters Table 22 resumes the applicable SPM and I2C parameters for each GPIO mode. SPM I2C GpioMode GpioOutPwrUp GpioAutoligth GpioPolarity GpioIntensityOn GpioIntensityOff GpioFunction GpioIncFactor GpioDecFactor GpioIncTime GpioDecTime GpioOffDelay GpioPullUpDown GpioInterrupt GpioDebounce IrqSrc[4] GpiStat GpoCtrl GppPinId GppIntensity GPI X GPP X 1 X X 1 X 1 X X GPO X 2 X X X X X X X X X X X X X X X X X 3 X 1 X 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 Only if Autolight is OFF, else ignored Table 22 Applicable SPM/I2C Parameters vs. GPIO Mode Revision 7_6, June 12 © 2012 Semtech Corp. 53 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 6 I2C INTERFACE The I2C implemented on the SX8636 is compliant with: - standard (100kb/s), fast mode (400kb/s) - slave mode - 7 bit address (default 0x2B). The default address can be changed in the NVM at address 0x04. The host can use the I2C to read and write data at any time. The effective changes will be applied at the next processing phase (section 3.3). Three types of registers are considered: - status (read). 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 SX8636 is powered down. The SPM can be stored permanently in the NVM memory of the SX8636. 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 44. After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The SX8636 then Acknowledges [A] that it is being addressed, and the Master sends an 8 bit Data Byte consisting of the SX8636 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 44 I2C write The register address is incremented automatically when successive register data (WD1...WDn) is supplied by the master. Revision 7_6, June 12 © 2012 Semtech Corp. 54 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 6.2 I2C read The format of the I2C read is given in Figure 45. After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The SX8636 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 SX8636 responds with an Acknowledge [A] and the read Data byte (RD0). If the master needs to read more data it will acknowledge [A] and the SX8636 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 45 I2C read Revision 7_6, June 12 © 2012 Semtech Corp. 55 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 6.3 I2C Registers Overview Address Name R/W Description 0x00 IrqSrc read Interrupt Source 0x01 Reserved 0x02 CapStatLsb read Button Status LSB 0x03 Reserved 0x04 Reserved 0x05 Reserved 0x06 Reserved 0x07 GpiStat read GPI Status 0x08 SpmStat read SPM Status 0x09 CompOpMode read/write Compensation and Operating Mode 0x0A GpoCtrl read/write GPO Control 0x0B GppId read/write GPP Pin Selection 0x0C GppIntensity read/write GPP Intensity 0x0D SpmCfg read/write SPM Configuration 0x0E SpmBaseAddr read/write SPM Base Address 0x0F Reserved 0xAC SpmKeyMsb read/write SPM Key MSB 0xAD SpmkeyLsb read/write SPM Key LSB 0xB1 SoftReset read/write Software Reset Table 23 I2C Registers Overview Revision 7_6, June 12 © 2012 Semtech Corp. 56 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 6.4 Status Registers Address 0x00 Name Bits Description 7 Reserved 6 NVM burn interrupt flag 5 SPM write interrupt flag 4 GPI interrupt flag 3 Reserved 2 Buttons interrupt flag 1 Compensation interrupt flag 0 Operating Mode interrupt flag IrqSrc 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 24 Interrupt Source The delay between the actual event and the flags indicating the interrupt source may be one scan period. IrqSrc[6] is set once NVM burn procedure is completed. IrqSrc[5] is set once SPM write is effective. IrqSrc[4] is set if a GPI edge as programmed in GpioInterrupt occurred. GpiStat shows the detailed status of the GPI pins. IrqSrc[2] is set if a Button 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 either through automatic wakeup or via host request. CompOpmode shows the current operation mode. Revision 7_6, June 12 © 2012 Semtech Corp. 57 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Address 0x02 Name CapStatLsb Bits Description 7 Button 7 Touched 6 Button 6 Touched 5 Button 5 Touched 4 Button 4 Touched 3 Button 3 Touched 2 Button 2 Touched 1 Button 1 Touched 0 Button 0 Touched Button Touch status 0: Released (default) 1: Touched Table 25, Button status LSB Address 0x07 Name GpiStat Bits 7:0 Description Status of each individual GPI pin 0: Low 1: High GPI[7:0] Status Bits of non-GPI pins are set to 0. Table 26 I2C GPI status Address 0x08 Name Bits Description 7:4 reserved 3 NvmValid 2:0 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. NvmCount 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 Indicates if the current NVM is valid. 0: No – QSM is used 1: Yes – NVM is used SpmStat Table 27 I2C SPM status Revision 7_6, June 12 © 2012 Semtech Corp. 58 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 6.5 Control Registers Address Name Bits Description 7:3 Reserved*, write only ‘00000’ 2 0x09 Compensation Indicates/triggers compensation procedure 0: Compensation completed (default) 1: read -> compensation running ; write -> trigger compensation Operating Mode Indicates/programs** operating mode 00: Active mode (default) 01: Doze mode 10: Sleep mode 11: Reserved CompOpMode 1:0 Table 28 I2C compensation, operation modes * The reading of these reserved bits will return varying values. ** After the operating mode change (Active/Doze) the host should wait for INTB or 300ms before performing any I2C read access. Address Name 0x0A GpoCtrl Bits 7:0 Description GpoCtrl[7:0] Triggers ON/OFF state of GPOs when Autolight is OFF 0: OFF (ie go to IntensityOff) 1: ON (ie go to IntensityOn) Default is set by SPM parameter GpioOutPwrUp Bits of non-GPO pins are ignored. Table 29 I2C GPO Control Revision 7_6, June 12 © 2012 Semtech Corp. 59 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING Address 0x0B Name Bits Description 7:3 Reserved, write only ‘00000’ 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 30 I2C GPP Pin Identifier Address 0x0C Name GppIntensity Bits 7:0 Description 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 31 I2C GPP Intensity Address 0xB1 Name Bits Description SoftReset 7:0 Writing 0xDE followed by 0x00 will reset the chip. Table 32 I2C Soft Reset Revision 7_6, June 12 © 2012 Semtech Corp. 60 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 6.6 SPM Gateway Registers The SX8636 I2C interface offers two registers for exchanging the SPM data with the host. • SpmCfg • SpmBaseAddr Address 0x0D Name Bits Description 7:6 00: Reserved 5:4 Enables I2C SPM mode 00: OFF (default) 01: ON 10: Reserved 11: Reserved 3 Defines r/w direction of SPM 0: SPM write access (default) 1: SPM read access 2 Enables monitor mode (Cf. §6.8) 0: OFF 1: ON 1:0 00: Reserved SpmCfg Table 33 SPM access configuration Address Name 0x0E SpmBaseAddr Bits Description 7:0 SPM Base Address (modulo 8). The lowest address is 0x00 (default). The highest address is 0x78. Table 34 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 0xAC SpmKeyMsb Bits Description 7:0 SPM to NVM burn Key MSB Unlock requires writing data: 0x62 Table 35 SPM Key MSB Address 0xAD Name Bits Description SpmKeyLsb 7:0 SPM to NVM burn Key LSB Unlock requires writing data: 0x9D Table 36 SPM Key LSB Revision 7_6, June 12 © 2012 Semtech Corp. 61 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 6.6.1 SPM Write Sequence The SPM write can be done in any mode (Active, Doze, Sleep). Writing the SPM in Sleep is useful to avoid potential transient behaviors. The SPM must always be written in blocks of 8 bytes. The sequence is described below: 1. Set the I2C in SPM mode by writing “01” to SpmCfg[5:4] and SPM write access by writing ‘0’ to SpmCfg[3]. 2. Write the SPM base address to SpmBaseAddr (The base address needs to be a value modulo 8). 3. Write the eight consecutive bytes to I2C address 0, 1, 2, …7 4. Terminate by writing “000” to SpmCfg[5:3]. Figure 46: SPM Write Sequence The complete SPM can be written by repeating 16 times the cycles shown in Figure 46 using base addresses 0x00, 0x08, 0x10, …, 0x70, 0x78. Between each sequence the host should wait for INTB (Active/Doze) or 30ms in Sleep. In Active or Doze mode, once the SPM write sequence is actually applied, the INTB pin will be asserted and IrqSrc[5] set. In Sleep mode the SPM write can be actually applied with a delay of 30ms. The host clears the interrupt and IrqSrc[5] by reading the IrqSrc register. Revision 7_6, June 12 © 2012 Semtech Corp. 62 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 6.6.2 SPM Read Sequence The SPM read can be done in any mode (Active, Doze, Sleep). The SPM must always be read in blocks of 8 bytes. The sequence is described below: 1. Set the I2C in SPM mode by writing “01” to SpmCfg[5:4] and SPM read access by writing ‘1’ to SpmCfg[3]. 2. Write the SPM base address to SpmBaseAddr (The base address needs to be a value modulo 8). 3. Read the eight consecutive bytes from I2C address 0, 1, 2, …7 4. Terminate by writing “000” to SpmCfg[5:3]. Figure 47: SPM Read Sequence The complete SPM can be read by repeating 16 times the cycles shown in Figure 47 using base addresses 0x00, 0x08, 0x10, …, 0x70, 0x78. Revision 7_6, June 12 © 2012 Semtech Corp. 63 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 6.7 NVM burn The content of the SPM can be copied permanently (burned) into the NVM to be used as the new default parameters. The burning of the NVM can be done up to three times and must be done only when the SPM is completely written with the desired data. The NVM burn must be done in Active or Doze mode. Once the NVM burn process is terminated IrqSrc[6] will be set and INTB asserted. After a reset the burned NVM parameters will be copied into the SPM. The number of times the NVM has been burned can be monitored by reading NvmCount from the I2C register SpmStat[2:0]. Figure 48 Simplified Diagram NvmCount Figure 48 shows the simplified diagram of the NVM counter. The SX8636 is delivered with empty NVM and NvmCount set to zero. The SPM points to the QSM. Each NVM burn will increase the NvmCount. At the fourth NVM burn the SX8636 switches definitely to the QSM. The burning of the SPM into the NVM is done by executing a special sequence of four I2C commands. 1. Write the data 0x62 to the I2C register I2CKeyMsb. 2. Write the data 0x9D to the I2C register I2CKeyLsb. 3. Write the data 0xA5 to the I2C register I2CSpmBaseAddr. 4. Write the data 0x5A to the I2C register I2CSpmBaseAddr. Terminate the I2C write by a STOP. Terminate the I2C write by a STOP. Terminate the I2C write by a STOP. Terminate the I2C write by a STOP. This is illustrated in Figure 49. 1) S SA 0 A 0xAC A 0x62 A P 2) S SA 0 A 0xAD A 0x9D A P 3) S SA 0 A 0x0E A 0xA5 A P 4) S SA 0 A 0x0E A 0x5A A P S SA A P : Start condition : Slave address : Slave acknowledge : Stop condition From master to slave From slave to master Figure 49: NVM burn procedure Revision 7_6, June 12 © 2012 Semtech Corp. 64 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 6.8 Monitor Mode Monitor mode allows the host to read “real-time” sensor information (CAPxRaw, CAPxAvg, CAPxDiff). It is enabled by setting bit 2 of I2C register SpmCfg (address 0x0D). When enabled, it uses a specific monitor scan period (Cf below) and generates an interrupt every time a new full set of data is available (hence every scan period). Address Name 0xF9 Bits MonitorScanPeriod 7:0 Description Monitor Mode Scan Period 0x00: Reserved 0x01: 15ms … 0x0D: 195ms (default) … 0xFF: 255 x 15ms Monitor mode scan period is located at address 0xF9 can be written similarly as SPM data (Cf. §6.6.1). Interrupt is cleared normally by reading I2C register IrqSrc (address 0x00) but no specific flag is set. CAPxRaw/Avg/Diff data can be read similarly as SPM data (Cf. §6.6.2) Base address BA = 0xB4 is the beginning of the CAPxDiff data location and data are organized this way: 0xB4: CAP0Diff, MSB 0xB5: CAP0Diff, LSB 0xB6: CAP1Diff, MSB etc... Values are coded 16bits signed 2's complement format and updated at each scan period. Base address BA = 0x80 is the beginning of the CAPxRaw data location. Base address BA = 0x9A is the beginning of the CAPxAvg data location. Data should be read before the next interrupt occurs (i.e. within one scan period). Revision 7_6, June 12 © 2012 Semtech Corp. 65 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 7 APPLICATION INFORMATION 7.1 Typical Application Schematic . Figure 50 Typical Application Revision 7_6, June 12 © 2012 Semtech Corp. 66 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 7.2 Example of Touch+Proximity Module 7.2.1 Overview To demonstrate the proximity sensing feature of the SX863x family, a module has been designed and is illustrated in figure below. Figure 51 Touch+Proximity Module Overview The touch button controller is running in stand-alone (ie without host) and uses the Autolight mode to turn LEDs ON/OFF accordingly to the touch buttons and proximity sensing status. 7.2.2 Operation Module operation can be seen as 5 steps which are described in figure below 1. No finger => No proximity detected => All LEDs OFF 2. Finger approaches => Proximity 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 52 Touch+Proximity Module Operation Notes: - For better user experience, bicolor LEDs have been used here but one could decide to design a module with normal unicolor LEDs. In this case, step 3 above would simply consist in a higher (blue) intensity for the LED of the button touched. - For obvious demonstration purposes the overlay used here is transparent but in typical applications (TV, Monitor, Set-top box, etc) the overlay would be opaque enough so that when LEDs are OFF (ie no proximity detected) the PCB is not visible to the user. 7.2.3 Performance The proximity sensing distance of detection has been measured in these conditions: - CapProxEnable = ON Revision 7_6, June 12 © 2012 Semtech Corp. 67 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING - CapSensitivity = 7 (Max) - CapThreshold = 300 - Board main supplied and placed vertically ie same orientation as hand/finger - Finger pointing center button The results obtained are provided in table below: Palm Finger (natural position) Orthogonal finger (worst case) Distance of Detection ~10cm ~6cm ~4cm Table 37 Proximity Sensing Distance of Detection 7.2.4 Schematics Figure 53 Touch+Proximity Module Schematics Revision 7_6, June 12 © 2012 Semtech Corp. 68 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 7.2.5 Layout Figure 54 Touch+Proximity Module Layout - Top Figure 55 Touch+Proximity Module Layout - Mid1 Figure 56 Touch+Proximity Module Layout - Mid2 Figure 57 Touch+Proximity Module Layout - Bottom Revision 7_6, June 12 © 2012 Semtech Corp. 69 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 8 REFERENCES [1] Capacitive Touch Sensing Layout guidelines on www.semtech.com Revision 7_6, June 12 © 2012 Semtech Corp. 70 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING 9 PACKAGING INFORMATION 9.1 Package Outline Drawing SX8636 is assembled in a MLPQ-UT28 package as shown in Figure 58. A D PIN 1 INDICATOR (LASER MARK) DIM B E A2 A A A1 A2 b D D1 E E1 e L N aaa bbb DIMENSIONS INCHES MILLIMETERS MIN NOM MAX MIN NOM MAX .024 .001 (.006) .006 .008 .010 .154 .157 .161 .100 .104 .108 .154 .157 .161 .100 .104 .108 .016 BSC .012 .016 .020 28 .003 .004 .020 .000 0.60 0.02 (0.152) 0.15 0.20 0.25 3.90 4.00 4.10 2.55 2.65 2.75 3.90 4.00 4.10 2.55 2.65 2.75 0.40 BSC 0.30 0.40 0.50 28 0.08 0.10 0.50 0.00 SEATING PLANE aaa C C A1 LxN D1 E/2 E1 2 1 N e bxN D/2 bbb C A B NOTES: 1. CONTROLLING DIMENSIONS ARE IN MILLIMETERS (ANGLES IN DEGREES). 2. COPLANARITY APPLIES TO THE EXPOSED PAD AS WELL AS THE TERMINALS. Figure 58 Package Outline Drawing 9.2 Land Pattern The land pattern of MLPQ-UT28 package, 4 mm x 4 mm is shown in Figure 59. Revision 7_6, June 12 Figure 59 Land Pattern © 2012 Semtech Corp. 71 www.semtech.com SX8636 Low Power, Capacitive Button Touch Controller (8 sensors) with Enhanced LED Drivers and Proximity Sensing WIRELESS & SENSING © Semtech 2012 All rights reserved. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. No liability will be accepted by the publisher for any consequence of its use. Publication thereof does not convey nor imply any license under patent or other industrial or intellectual property rights. Semtech assumes no responsibility or liability whatsoever for any failure or unexpected operation resulting from misuse, neglect improper installation, repair or improper handling or unusual physical or electrical stress including, but not limited to, exposure to parameters beyond the specified maximum ratings or operation outside the specified range. SEMTECH PRODUCTS ARE NOT DESIGNED, INTENDED, AUTHORIZED OR WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT APPLICATIONS, DEVICES OR SYSTEMS OR OTHER CRITICAL APPLICATIONS. INCLUSION OF SEMTECH PRODUCTS IN SUCH APPLICATIONS IS UNDERSTOOD TO BE UNDERTAKEN SOLELY AT THE CUSTOMER’S OWN RISK. Should a customer purchase or use Semtech products for any such unauthorized application, the customer shall indemnify and hold Semtech and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs damages and attorney fees which could arise. Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners. CONTACT INFORMATION Semtech Corporation Wireless and Sensing Products Division 200 Flynn Road, Camarillo, CA 93012 Phone: (805) 498-2111 Fax: (805) 498-3804 Revision 7_6, June 12 © 2012 Semtech Corp. 72 www.semtech.com