SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING GENERAL DESCRIPTION KEY PRODUCT FEATURES The SX9500 is a low-cost, very low power 4-channel capacitive controller that can operate either as a proximity or button sensor. The SX9500 includes sophisticated on-chip auto-calibration circuitry to regularly perform sensitivity adjustments, maintaining peak performance over a wide variation of temperature, humidity and noise environments, providing simplified product development and enhanced performance. 2.7 – 5.5V Input Supply Voltage Capacitive Sensor Inputs Down to 0.08 fF Capacitance Resolution Stable Proximity & Touch Sensing With Temperature Capacitance Offset Compensation to 30pF Active Sensor Guarding Automatic Calibration Ultra Low Power Consumption: The SX9500 operates directly from an input supply voltage of 2.7 to 5.5V, and includes a separate I2C serial bus supply input to enable communication with 1.8 – 5.5V hosts. The I2C serial communication bus reports proximity or touch detection and is used to facilitate parameter settings adjustment. Upon a proximity detection, the NIRQ output asserts, enabling the user to either determine the relative proximity distance, or simply obtain an indication of detection. Active Mode: Doze Mode: Sleep Mode: 170 uA 18 uA 2.5 uA 400KHz I2C Serial Interface Four programmable I2C Sub-Addresses Input Levels Compatible with 1.8V Host Processors Open Drain NIRQ Interrupt pin Three (3) Reset Sources: POR, NRST pin, Soft Reset -40°C to +85°C Operation Compact Size: 3 x 3mm Thin QFN package Pb & Halogen Free, RoHS/WEEE compliant A dedicated transmit enable (TXEN) pin is available to synchronize capacitive measurements for applications that require synchronous detection, enabling very low supply current and high noise immunity by only measuring proximity when requested. APPLICATIONS • • • Notebooks Tablets Mobile Appliances ORDERING INFORMATION Part Number SX9500IULTRT SX9500EVKA 1 1 Package Marking QFN-20 ZND8 Eval. Kit 3000 Units/reel TYPICAL APPLICATION CIRCUIT Revision 4 February 4, 2014 © 2014 Semtech Corporation 1 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING Table of Contents GENERAL DESCRIPTION ........................................................................................................................ 1 KEY PRODUCT FEATURES..................................................................................................................... 1 APPLICATIONS....................................................................................................................................... 1 ORDERING INFORMATION...................................................................................................................... 1 TYPICAL APPLICATION CIRCUIT ............................................................................................................ 1 1 GENERAL DESCRIPTION ............................................................................................................... 4 1.1 1.2 1.3 1.4 Pin Diagram Marking Information Pin Description Acronyms 4 4 5 5 ELECTRICAL CHARACTERISTICS ................................................................................................. 6 2 2.1 2.2 2.3 2.4 3 Absolute Maximum Ratings Operating Conditions Thermal Characteristics Electrical Specifications PROXIMITY SENSING INTERFACE ................................................................................................. 9 3.1 3.2 3.3 Introduction Scan Period Analog Front-End (AFE) 3.3.1 Capacitive Sensing Basics 3.3.2 AFE Block Diagram 3.3.3 Capacitance-to-Voltage Conversion (C-to-V) 3.3.4 Shield Control 3.3.5 Offset Compensation 3.3.6 Analog-to-Digital Conversion (ADC) 3.4 Digital Processing 3.4.1 Overview 3.4.2 PROXRAW Update 3.4.3 PROXUSEFUL Update 3.4.4 PROXAVG Update 3.4.5 PROXDIFF Update 3.4.6 PROXSTAT Update 3.5 Host Operation 3.6 Operational Modes 3.6.1 Active 3.6.2 Doze 3.6.3 Sleep 3.6.4 TXEN Pin 4 9 9 10 10 12 12 12 12 13 13 13 15 15 16 18 18 19 20 20 20 20 20 I2C INTERFACE ........................................................................................................................... 21 4.1 4.2 4.3 5 Introduction I2C Write I2C Read 21 21 21 RESET ......................................................................................................................................... 23 5.1 5.2 5.3 6 6 6 6 7 Power-up NRST Pin Software Reset 23 23 24 INTERRUPT ................................................................................................................................. 25 Revision 4 February 4, 2014 © 2014 Semtech Corporation 2 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 6.1 6.2 7 Power-up Assertion and Clearing PINS DESCRIPTION ..................................................................................................................... 26 7.1 7.2 7.3 7.4 VDD and SVDD TXEN Capacitive Sensing Interface (CS0, CS1, CS2, CS3, CSG) Host Interface 7.4.1 NIRQ 7.4.2 SCL, NRST and TXEN 7.4.3 SDA 26 26 26 26 26 27 27 REGISTERS ................................................................................................................................. 28 8 8.1 8.2 9 Overview Detailed Description 28 29 APPLICATION INFORMATION ...................................................................................................... 33 9.1 9.2 10 25 25 Typical Application Circuit External Components Recommended Values 33 33 PACKAGING INFORMATION ........................................................................................................ 34 10.1 10.2 Revision 4 Outline Drawing Land Pattern February 4, 2014 34 35 © 2014 Semtech Corporation 3 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 1 GENERAL DESCRIPTION 1.1 Pin Diagram Figure 1: Pin Diagram 1.2 Marking Information ZND8 yyww xxxx yyww= Date Code xxxx = Lot Number Figure 2: Marking Information Revision 4 February 4, 2014 © 2014 Semtech Corporation 4 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 1.3 Pin Description Number Name Type Description 1 CSG Analog Capacitive Sensor Guard/Shield 2 CS3 Analog Capacitive Sensor 3 3 CS2 Analog Capacitive Sensor 2 4 CS1 Analog Capacitive Sensor 1 5 CS0 Analog Capacitive Sensor 0 6 GND Ground Ground 7 NC Not Used Do Not Connect 8 NC Not Used Do Not Connect 9 NC Not Used Do Not Connect 10 NC Not Used Do Not Connect 11 VDD Power Core power supply 12 SVDD Power Host interface power supply. Must be ≤VDD at all times (including during power-up and power-down) 13 NIRQ Digital Output 14 SCL Digital Input I2C Clock, requires pull-up resistor to SVDD 15 SDA Digital I/O I2C Data, requires pull-up resistor to SVDD 16 TXEN Digital Input Transmit Enable, active HIGH (Tie to SVDD if not used). 17 NRST External reset, active LOW (Tie to SVDD if not used). 18 A1 Digital Input Input Digital Input 19 A0 Digital Input I2C Sub-Address, connect to GND or VDD 20 GND Ground Ground DAP GND Ground Exposed Pad. Connect to Ground Interrupt request, active LOW, requires pull-up resistor to SVDD I2C Sub-Address, connect to GND or VDD Table 1: Pin Description 1.4 Acronyms DAP RF Revision 4 Die Attach Paddle Radio Frequency February 4, 2014 © 2014 Semtech Corporation 5 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution 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 “Operating Conditions”, is not implied. Exposure to Absolute Maximum Rating conditions for extended periods may affect device reliability and proper functionality. Parameter Symbol Min Max Unit VDD -0.5 6.0 SVDD -0.5 6.0 Input Voltage (non-supply pins) VIN -0.5 VDD+0.3 Input Current (non-supply pins) IIN -10 10 Operating Junction Temperature TJCT -40 125 Reflow Temperature TRE - 260 Storage Temperature TSTOR -50 150 ESDHBM 8 - kV Symbol Min Max Unit VDD 2.7 5.5 SVDD 1.65 VDD TA -40 85 Supply Voltage ESD HBM (Human Body model, to JESD22-A114) V mA °C Table 2: Absolute Maximum Ratings 2.2 Operating Conditions Parameter Supply Voltage V Ambient Temperature °C Table 3: Operating Conditions Note: During power-up or power-down, SVDD must be less than or equal to VDD 2.3 Thermal Characteristics Parameter Thermal Resistance – Junction to Air (Static Airflow) Symbol Typical Unit θJA 34 °C/W Table 4: Thermal Characteristics Note: θJA is calculated from a package in still air, mounted to 3" x 4.5", 4-layer FR4 PCB with thermal vias under exposed pad per JESD51 standards. Revision 4 February 4, 2014 © 2014 Semtech Corporation 6 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 2.4 Electrical Specifications All values are valid within the operating conditions unless otherwise specified. Typical values are given for TA= +25°C, VDD=SVDD=3.3V unless otherwise specified. Parameter Symbol Conditions Min Typ Max ISLEEP Power down, all analog circuits shut down. (I2C listening) - 2.5 - Doze (all sensors enabled) IDOZE SCANPERIOD = 200ms DOZEPERIOD = 2xSCANPERIOD FREQ = 167kHz RESOLUTION = Medium VDD = 5V - 18 - Active (all sensors enabled) IACTIVE SCANPERIOD = 30ms FREQ = 167kHz RESOLUTION = Medium VDD = 5V - 170 - Output Current at Output Low Voltage IOL VOL = 0.4V 6 - - SVDD > 2V - - 0.4 Maximum Output LOW Voltage VOL(Max) SVDD ≤ 2V - - 0.2 x SVDD Unit Current Consumption Sleep (no sensor enabled) uA Outputs: SDA, NIRQ mA V Inputs: SCL, SDA, TXEN Input logic high VIH 0.8 x SVDD - SVDD + 0.3 Input logic low VIL -0.3 - 0.25 x SVDD Input leakage current IL CMOS input -1 - 1 SVDD > 2V - 0.05x SVDD - SVDD≤ 2V - 0.1x SVDD - - 100 - V VHYS Hysteresis Delay between TXEN rising TXENACTDLY edge and SX9500 starting measurements TXEN Delay uA V µs Inputs: A0, A1 Input logic high VIH 0.7 x VDD - VDD + 0.3 Input logic low VIL -0.3 - 0.3 x VDD SVDD> 2V 0.7 x SVDD - SVDD ≤ 2V 0.75 x SVDD - SVDD> 2V - - 0.6 SVDD ≤ 2V - - 0.3 x SVDD TRESETPW 2 - - µs TPOR - 1 - ms V Input: NRST Input logic high VIH SVDD + 0.3 V Input logic low VIL NRST minimum pulse width Start-up Power-up time Table 5: Electrical Specifications Revision 4 February 4, 2014 © 2014 Semtech Corporation 7 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING Parameter Symbol Conditions Min Typ Max Unit kHz I2C Timing Specifications (Cf. Figure 3 and Figure 4 below) SCL clock frequency fSCL - - 400 SCL low period tLOW 1.3 - - SCL high period tHIGH 0.6 - - Data setup time tSU;DAT 0.1 - - Data hold time tHD;DAT 0 - - Repeated start setup time tSU;STA 0.6 - - Start condition hold time tHD;STA 0.6 - - Stop condition setup time tSU;STO 0.6 - - Bus free time between stop and start tBUF 1.3 - - Input glitch suppression tSP - - 50 us Note 1 ns Note 1: Minimum glitch amplitude is 0.7VDD at High level and Maximum 0.3VDD at Low level. Table 6: I2C Timing Specifications Figure 3: I2C Start and Stop Timing Figure 4: I2C Data Timing Revision 4 February 4, 2014 © 2014 Semtech Corporation 8 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 3 PROXIMITY SENSING INTERFACE 3.1 Introduction The purpose of the proximity sensing interface is to detect when a conductive object (usually a body part i.e. finger, palm, face, etc) is in the proximity of the system. Note that proximity sensing can be done thru the air or thru a solid (typically plastic) overlay (also called “touch” sensing). The chip’s proximity sensing interface is based on capacitive sensing technology. An overview is given in figure below. Finger, palm, face, lap, etc Sensor Shield CSx CSG Analog Front-End (AFE) PROXSTAT Digital 0 1 0 Processing SX9500 Figure 5: Proximity Sensing Interface Overview The sensor can be a simple copper area on a PCB or FPC for example. Its capacitance (to ground) will vary when a conductive object is moving in its proximity. The optional shield can be also be a simple copper area on a PCB or FPC below/under/around the sensor. It is used to protect the sensor against potential surrounding noise sources and improve its global performance. It also brings directivity to the sensing, for example sensing objects approaching from top only. The analog front-end (AFE) performs the raw sensor’s capacitance measurement and converts it into a digital value. It also controls the shield. See §3.3 for more details. The digital processing block computes the raw capacitance measurement from the AFE and extracts a binary information PROXSTAT corresponding to the proximity status, i.e. object is “Far” or “Close”. It also triggers AFE operations (compensation, etc). See §3.4 for more details. 3.2 Scan Period To save power and since the proximity event is slow by nature, the chip will be waken-up regularly at every programmed scan period (SCANPERIOD) to first sense sequentially each of the enabled CSx pins and then process new proximity samples/info. The chip will be in idle mode most of the time. This is illustrated in figure below Figure 6: Proximity Sensing Sequencing Revision 4 February 4, 2014 © 2014 Semtech Corporation 9 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING The sensing and processing phase’s durations vary with the number of sensors enabled, the sampling frequency, and the resolution programmed. During the Idle phase, the SX9500‘s analog circuits are turned off. Upon expiry of the idle timer, a new scan period cycle begins. The scan period determines the minimum reaction time (actual/final reaction time also depends on debounce and filtering settings) and can be programmed from 30ms to 400ms. 3.3 Analog Front-End (AFE) 3.3.1 Capacitive Sensing Basics Capacitive sensing is the art of measuring a small variation of capacitance in a noisy environment. As mentioned above, the chip’s proximity sensing interface is based on capacitive sensing technology. In order to illustrate some of the user choices and compromises required when using this technology it is useful to understand its basic principles. To illustrate the principle of capacitive sensing we will use the simplest implementation where the sensor is a copper plate on a PCB. The figure below shows a cross-section and top view of a typical capacitive sensing implementation. The sensor connected to the chip is a simple copper area on top layer of the PCB. It is usually surrounded (shielded) by ground for noise immunity (shield function) but also indirectly couples via the grounds areas of the rest of the system (PCB ground traces/planes, housing, etc). For obvious reasons (design, isolation, robustness …) the sensor is stacked behind an overlay which is usually integrated in the housing of the complete system. PCB copper Overlay PCB dielectric Sensor Cut view Top view Ground Figure 7: Typical Capacitive Sensing Implementation When the conductive object to be detected (finger/palm/face, etc) is not present, the sensor only sees an inherent capacitance value CEnv created by its electrical field’s interaction with the environment, in particular with ground areas. When the conductive object (finger/palm/face, etc) approaches, the electrical field around the sensor will be modified and the total capacitance seen by the sensor increased by the user capacitance CUser. This phenomenon is illustrated in the figure below. Revision 4 February 4, 2014 © 2014 Semtech Corporation 10 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING Figure 8: Proximity Effect on Electrical Field and Sensor Capacitance The challenge of capacitive sensing is to detect this relatively small variation of CSensor (CUser usually contributes for a few percent only) and differentiate it from environmental noise (CEnv also slowly varies together with the environment characteristics like temperature, etc). For this purpose, the chip integrates an auto offset compensation mechanism which dynamically monitors and removes the CEnv component to extract and process CUser only. See §3.3.5 for more details. In first order, CUser can be estimated by the formula below: CUser = ε 0 ⋅ εr ⋅ A d A is the common area between the two electrodes hence the common area between the user’s finger/palm/face and the sensor. d is the distance between the two electrodes hence the proximity distance between the user and the system. ε 0 is the free space permittivity and is equal to 8.85 10e-12 F/m (constant) ε r is the dielectric relative permittivity. Typical permittivity of some common materials is given in the table below. Material Glass FR4 Acrylic Glass Wood Air Typical 8 5 3 2 1 εr Table 7: Typical Permittivity of Some Common Materials From the discussions above we can conclude that the most robust and efficient design will be the one that minimizes CEnv value and variations while improving CUser. Revision 4 February 4, 2014 © 2014 Semtech Corporation 11 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 3.3.2 AFE Block Diagram Figure 9: Analog Front-End Block Diagram 3.3.3 Capacitance-to-Voltage Conversion (C-to-V) The sensitivity of the interface is defined by RANGE and GAIN parameters. PROXFREQ defines the operating frequency of the interface and should be set as high as possible for power consumption reasons. 3.3.4 Shield Control SHIELDEN allows enabling or disabling the shield function. 3.3.5 Offset Compensation Offset compensation consists in performing a one-time measurement of CEnv and subtracting it to the total capacitance CSensor in order to feed the ADC with the closest contribution of CUser only. Figure 10: Offset Compensation Block Diagram The ADC input CUser is the total capacitance CSensor to which CEnv is subtracted. Revision 4 February 4, 2014 © 2014 Semtech Corporation 12 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING There are five possible compensation sources which are illustrated in the figure below. When set to 1 by any of these sources, COMPSTAT will only be reset once the compensation is completed. Figure 11: Compensation Request Sources Reset: a compensation for all sensors is automatically requested when a reset is performed (power-up, NRST pin, RegReset) COMPDONEIRQ (I2C): a compensation for all sensors can be manually requested anytime by the host through I2C interface by writing a 1 into COMPDONEIRQ. AVGTHRESH: a compensation for all sensors or only the affected one (depending on COMPMETHOD) can be automatically requested if it is detected that CEnv has drifted beyond a predefined range programmed by the host. COMPPRD: a compensation can be automatically requested at a predefined rate programmed by the host. STUCK: a compensation can be automatically requested if it is detected that the proximity “Close” state lasts longer than a predefined duration programmed by the host. Please note that the compensation request flag can be set anytime but the compensation itself is always done at the beginning of a scan period to keep all parameters coherent. Also, when compensation occurs, all PROXSTAT flags turn OFF (ie no proximity detected) independently from the user’s potential actual presence. 3.3.6 Analog-to-Digital Conversion (ADC) An ADC is used to convert the analog capacitance information into a digital word PROXRAW. 3.4 Digital Processing 3.4.1 Overview The main purpose of the digital processing block is to convert the raw capacitance information coming from the AFE (PROXRAW) into a robust and reliable digital flag (PROXSTAT) indicating if something is close to the proximity sensor. The offset compensation performed in the AFE is a one-time measurement. However, the environment capacitance CEnv may vary with time (temperature, nearby objects, etc). Hence, in order to get the best estimation of CUser (PROXDIFF) it is needed to dynamically track and subtract CEnv variations. This is performed by filtering PROXUSEFUL to extract its slow variations (PROXAVG). PROXDIFF is then compared to user programmable threshold (PROXTHRESH) to extract PROXSTAT flag. Revision 4 February 4, 2014 © 2014 Semtech Corporation 13 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING Figure 12: Digital Processing Block Diagram Digital processing sequencing is illustrated in figure below. At every scan period wake-up, the block updates sequentially PROXRAW, PROXUSEFUL, PROXAVG, PROXDIFF and PROXSTAT before going back to Idle mode. Figure 13: Digital Processing Sequencing Digital processing block also updates COMPSTAT (set when compensation is currently pending execution or completion) Revision 4 February 4, 2014 © 2014 Semtech Corporation 14 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 3.4.2 PROXRAW Update PROXRAW update consists mainly in starting the AFE and waiting for the new PROXRAW values (one for each CSx/sensor pin) to be ready. If compensation was pending it is performed first. Figure 14: ProxRaw Update Note that PROXRAW is not available in the “Sensor Data Readback” section of the registers. If needed it can be observed by setting RAWFILT=00 and reading PROXUSEFUL. 3.4.3 PROXUSEFUL Update PROXUSEFUL update consists in filtering PROXRAW upfront to remove its potential high frequencies components(system noise, interferer, etc) and extract only user activity (few Hz max) and slow environment changes. Figure 15: PROXUSEFUL Update Revision 4 February 4, 2014 © 2014 Semtech Corporation 15 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 3.4.4 PROXAVG Update PROXAVG update consists in averaging PROXUSEFUL to ignore its “fast” variations (i.e. user finger/palm/hand) and extract only the very slow variations of environment capacitance CEnv. One can program a debounced threshold (AVGTHRESH/AVGDEB) to define a range within which PROXAVG can vary without triggering compensation (i.e. small acceptable environment drift). Large positive values of PROXUSEFUL are considered as normal (user finger/hand/head) but large negative values are considered abnormal and should be compensated quickly. For this purpose, the averaging filter coefficient can be set independently for positive and negative variations via AVGPOSFILT and AVGNEGFILT. Typically we have AVGPOSFILT > AVGNEGFILT to filter out (abnormal) negative events faster. To prevent PROXAVG to be “corrupted” by user activity (should only reflect environmental changes) it is frozen when proximity is detected. Figure 16: ProxAvg vs Proximity Event Revision 4 February 4, 2014 © 2014 Semtech Corporation 16 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING Figure 17: ProxAvg Update Revision 4 February 4, 2014 © 2014 Semtech Corporation 17 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 3.4.5 PROXDIFF Update PROXDIFF update consists in the complementary operation i.e. subtracting PROXAVG to PROXUSEFUL to ignore slow capacitances variations (CEnv) and extract only the user related variations i.e. CUser. Figure 18: ProxDiff Update Note that only the 12 upper bits of [PROXUSEFUL – PROXAVG] are kept for PROXDIFF. 3.4.6 PROXSTAT Update PROXSTAT update consists in taking PROXDIFF information (CUser), comparing it with a user programmable threshold PROXTHRESH and finally updating PROXSTAT accordingly. When PROXSTAT=1, PROXAVG is frozen to prevent the user proximity signal averaging and hence absorbed into CEnv. Figure 19: PROXSTAT Update Revision 4 February 4, 2014 © 2014 Semtech Corporation 18 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 3.5 Host Operation An interrupt can be triggered when the user is detected to be close (in range), detected to be far (out of range), or both (CLOSEIRQEN, FARIRQEN). User in User out of range SCANPERIOD tick PROXSTAT NIRQ I2C Read RegIrqSrc Idle Proximity Sensing (Analog + Digital) Figure 20: Proximity Sensing Host Operation (RegIrqMsk[6:3] = 1100) An interrupt can also be triggered at the end of each proximity sensing operation, indicating to the host when the proximity sensing block is running (CONVDONEIRQEN). This may be used by the host to synchronize noisy system operations or to read sensor data (PROXUSEFUL, PROXAVG, PROXDIFF) synchronously for monitoring purposes. User in User out of range SCANPERIOD tick PROXSTAT NIRQ I2C Read Idle Proximity Sensing (Analog + Digital) Figure 21: Proximity Sensing Host Operation (RegIrqMsk[6:3] = 0001) In both cases above, an interrupt can also be triggered at the end of compensation (COMPDONEIRQEN). Revision 4 February 4, 2014 © 2014 Semtech Corporation 19 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 3.6 3.6.1 Operational Modes Active Active mode has the shortest scan periods, typically 30ms. In this mode, all enabled sensors are scanned and information data is processed within this interval. The Active scan period is user configurable (SCANPERIOD) and can be extended up to 400ms. 3.6.2 Doze In some applications, the reaction/sensing time needs to be fast when the user is present (proximity detected), but can be slow when not detection has been done for some time. The Doze mode, when enabled (DOZEEN), allows the chip to automatically switch between a fast scan period (SCANPERIOD) during proximity detection and a slow scan period (DOZEPERIOD) when no proximity is being detected (up to 6.4s). This allows reaching low average power consumption values at the expense obviously of longer reaction times. As soon as proximity is detected on any sensor, the chip will automatically switch to Active mode while when it has not detected an object for DOZEPERIOD, it will automatically switch to Doze mode. 3.6.3 Sleep Sleep mode can be entered by disabling all sensors (SENSOREN=0000). It places the SX9500 in its lowest power mode, with sensor scanning completely disabled and idle period set to continuous. In this mode, only the I2C serial bus is active. Enabling any sensor will make the chip leave Sleep mode (for Doze if enabled, else Active mode) 3.6.4 TXEN Pin The TXEN input enables proximity sensing when HIGH, likewise when the TXEN input is LOW, the SX9500 is in Sleep mode. Specifically, on the rising edge of TXEN the SX9500 will begin measuring the sensors normally at the programmed rate (SCANPERIOD, DOZEPERIOD) as long as TXEN remains HIGH. When TXEN goes LOW the current measurement sequence will complete and then measurement will cease until the next rising edge of TXEN. This feature can be used to synchronize proximity sensing with noisy and/or RF activity for example. Revision 4 February 4, 2014 © 2014 Semtech Corporation 20 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 4 I2C INTERFACE 4.1 Introduction The I2C implemented on the SX9500 and used by the host to interact with it is compliant with: - Standard (100kb/s) and fast mode (400kb/s) - Slave mode - 7-bit address (default is 0x28 assuming A1=A0=0) The SX9500 has two I/O pins (A0 and A1) that provides four possible, user selectable I2C addresses: A1 0 0 1 1 A0 0 1 0 1 Address 0x28 0x29 0x2A 0x2B Table 8: I2C Sub-Address Selection The host can use the I2C to read and write data at any time, and these changes are effective immediately. Therefore the user should ideally disable the sensor before changing settings, or discard the results while changing. 4.2 I2C Write The format of the I2C write is given in Figure 12. After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The SX9500 then Acknowledges [A] that it is being addressed, and the Master sends an 8 bit Data Byte consisting of the SX9500 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 22: I2C Write The register address is incremented automatically when successive register data (WD1...WDn) is supplied by the master. 4.3 I2C Read The format of the I2C read is given in Figure 13. After the start condition [S], the slave address (SA) is sent, followed by an eighth bit (‘0’) indicating a Write. The SX9500 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 SX9500 responds with an Acknowledge [A] and the read Revision 4 February 4, 2014 © 2014 Semtech Corporation 21 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING Data byte (RD0). If the master needs to read more data it will acknowledge [A] and the SX9500 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 23: I2C Read The register address is incremented automatically when successive register data (RD1...RDn) is retrieved by the master. Revision 4 February 4, 2014 © 2014 Semtech Corporation 22 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 5 RESET 5.1 Power-up During a power-up condition, the NIRQ output is HIGH until VDD has met the minimum input voltage requirements and a TPOR time has expired upon which, NIRQ asserts to a LOW condition indicating the SX9500 is initialized. The host must perform an I2C read of RegIrqSrc to clear this NIRQ status. The SX9500 is then ready for normal I2C communication and is operational. Figure 24: Power-up vs. NIRQ 5.2 NRST Pin When the host asserts NRST LOW (for min. TRESETPW) and then HIGH, the SX9500 will reset its internal registers and will become active after TPOR. When not used, this pin must be pulled high to SVDD. Figure 25: Hardware Reset Revision 4 February 4, 2014 © 2014 Semtech Corporation 23 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 5.3 Software Reset The host can also perform a reset anytime by writing 0xDE into RegReset. The NIRQ output will be asserted LOW and the Host is required to perform an I2C read to clear this NIRQ status. High SX9500 Ready NIRQ Low HOST issues a soft Reset HOST clears the Interrupt Figure 26: Software Reset Revision 4 February 4, 2014 © 2014 Semtech Corporation 24 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 6 INTERRUPT Except RESETIRQ, all interrupt sources are disabled by default upon power-up and resets, and thus must be enabled by the host. Any or all of the following interrupts can be enabled by writing a “1” into the appropriate locations within the RegIrqMsk register: • Close (proximity detected) • Far (proximity un-detected) • Compensation completed • Conversion completed The interrupt status can be read from RegIrqSrc for each of these interrupt sources. 6.1 Power-up During initial power-up, the NIRQ output is HIGH. Once the SX9500 internal power-up sequence has completed, NIRQ is asserted LOW, signaling that the SX9500 is ready. The host must perform a read to RegIrqSrc to acknowledge and the SX9500 will clear the interrupt and release the NIRQ line. 6.2 Assertion and Clearing The NIRQ can be asserted in either the Active or Doze mode during a scan period. The NIRQ will be automatically cleared after the host performs a read of RegIrqSrc (which content will be cleared as well). Revision 4 February 4, 2014 © 2014 Semtech Corporation 25 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 7 PINS DESCRIPTION 7.1 VDD and SVDD These are the device supply voltages. VDD is the supply voltage for the internal core. SVDD is the supply voltage for the host interface. NOTE: SVDD MUST be equal or lower than VDD at all times. 7.2 TXEN This signal can be used in many applications if a conversion trigger/enable is needed. This input pin synchronizes the Capacitance Sensing inputs in systems that need to (for example) transmit RF signals. When this signal is active, SX9500 performs capacitive measurements. If this input becomes inactive during the middle of a measurement, the SX9500 will complete all remaining measurements and will enter sleep mode until TXEN goes active again. 7.3 Capacitive Sensing Interface (CS0, CS1, CS2, CS3, CSG) The Capacitance Sensing input pins CS0, CS1, CS2 and CS3 are connected directly to the Capacitance Sensing Interface circuitry which converts the sensed capacitance into digital values. The Capacitive Sensor Guard (CSG) output provides a guard reference to minimize the parasitic sensor pin capacitances to ground. Capacitance sensor pins which are not used must not be connected. Additionally, CSx pins must be connected directly to the capacitive sensors using a minimum length circuit trace to minimize external “noise” pick-up. The capacitance sensor and capacitive sensor guard pins are protected from ESD events to VDD and GROUND. 7.4 Host Interface The Host Interface consists of: NIRQ, NRST, SCL, SDA, and TXEN. These signals are discussed below. 7.4.1 NIRQ The NIRQ pin is an open drain output that requires an external pull-up resistor (1...10 kOhm). The NIRQ pin is protected from ESD events to VDD and GROUND. SVDD VDD R_INT NIRQ NIRQ to Host INT SX9500 Figure 27: NIRQ Output Simplified Diagram Revision 4 February 4, 2014 © 2014 Semtech Corporation 26 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 7.4.2 SCL, NRST and TXEN The SCL, NRST and TXEN pins are high impedance input pins that require an external pull-up resistor (1..10 kOhm). NRST and TXEN can be connected without the requirement for a pull-up resistor if driven from a pushpull host output. These pins are protected from ESD events to VDD and GROUND. SVDD VDD R SCL_IN/TXEN_IN/NRST_IN From Host SCL/TXEN/NRST Figure 28: SCL/TXEN/NRST 7.4.3 SDA SDA is an I/O pin that requires an external pull-up resistor (1…10 kOhm). The SDA I/O pin is protected to VDD and GROUND. SVDD VDD R_SDA SDA To/From Host SDA_IN SDA_OUT Figure 29: SDA Simplified Diagram Revision 4 February 4, 2014 © 2014 Semtech Corporation 27 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 8 REGISTERS 8.1 Overview The SX9500 allows the user full parameter customization for sensor sensitivity, hysteresis, detection thresholds, etc. Custom parameters are controlled thru the volatile registers below and must be uploaded by the host thru I2C after power-up or after a reset. Address 0x00 0x01 0x03 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0D 0x0E 0x20 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x7F Name RegIrqSrc RegStat RegIrqMsk RegProxCtrl0 RegProxCtrl1 RegProxCtrl2 RegProxCtrl3 RegProxCtrl4 RegProxCtrl5 RegProxCtrl6 RegProxCtrl7 RegProxCtrl8 RegSensorSel RegUseMsb RegUseLsb RegAvgMsb RegAvgLsb RegDiffMsb RegDiffLsb RegOffsetMsb RegOffsetLsb RegReset Default 0x80 0x0F 0x00 0x0F 0x40 0x08 0x40 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 Description Interrupt & Status Proximity Sensing Control Sensor Data Readback Software Reset Table 9: Registers Overview NOTES: 1) Addresses not listed above are reserved and should not be written. 2) Reserved bits should be left to their default value unless otherwise specified. Revision 4 February 4, 2014 © 2014 Semtech Corporation 28 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 8.2 Detailed Description Addr. Name 0x00 RegIrqSrc 0x01 0x03 RegStat RegIrqMsk R/W 7 Variable Default Interrupt & Status RESETIRQ 1 6 CLOSEIRQ 0 5 FARIRQ 0 R/W 4 COMPDONEIRQ 0 R 3 CONVDONEIRQ 0 R 2:1 0 7 Reserved TXENSTAT PROXSTAT3 00 0 0 6 PROXSTAT2 0 5 PROXSTAT1 0 4 PROXSTAT0 0 3:0 COMPSTAT 1111 7 6 5 4 3 2:0 Reserved 0 CLOSEIRQEN 0 FARIRQEN 0 COMPDONEIRQEN 0 CONVDONEIRQEN 0 Reserved 000 Proximity Sensing Control Reserved 0 SCANPERIOD 000 R R R/W R 0x06 RegProxCtrl0 R/W Bits 7 6:4 3:0 Revision 4 February 4, 2014 SENSOREN 1111 © 2014 Semtech Corporation 29 Function Reset interrupt source status. (i.e. reset occurred) Close interrupt source status. (i.e. PROXSTATx rising edge) Far interrupt source status. (i.e. PROXSTATx falling edge) Compensation interrupt source status. (i.e. compensation occurred) When set to 1, triggers compensation Conversion interrupt source status. (i.e. new set of sensor data available) Indicates current TXEN pin status. Indicates if proximity is being detected for CS3 (i.e. sensor’s PROXDIFF value is above detection threshold) Indicates if proximity is being detected for CS2 (i.e. sensor’s PROXDIFF value is above detection threshold) Indicates if proximity is being detected for CS1 (i.e. sensor’s PROXDIFF value is above detection threshold) Indicates if proximity is being detected for CS0 (i.e. sensor’s PROXDIFF value is above detection threshold) Indicates which capacitive sensor(s) has a compensation pending. [3:0] = [CS3, CS2, CS1, CS0] Enables the close interrupt. Enables the far interrupt. Enables the compensation interrupt. Enables the conversion interrupt. Defines the Active scan period : 000: 30 ms (Typ.) 001: 60 ms 010: 90 ms 011: 120 ms 100: 150 ms 101: 200 ms 110: 300 ms 111: 400 ms Low values will allow fast reaction time while high values will provide low power consumption. Enables sensor pins. www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING [3:0] = [CS3, CS2, CS1, CS0] 0x07 RegProxCtrl1 R/W 7:6 SHIELDEN R/W R/W 5:2 1:0 Reserved RANGE 01 0000 00 Enables shield function on CSG pin: 00: Off, high impedance. 01: On (Typ.) 1x: Reserved Defines the input capacitance range: 00: Large (typ. +/-7.3pF FS) 01: Medium Large (typ. +/-3.7pF FS) 10: Medium Small (typ. +/-3pF FS) 11: Small (typ. +/-2.5pF FS) This parameter can be seen as an analog gain (small range = high gain) Full scale (FS) values assume no digital gain. 0x08 0x09 0x0A RegProxCtrl2 RegProxCtrl3 RegProxCtrl4 Revision 4 R/W R/W R/W February 4, 2014 7 6:5 Reserved GAIN 0 00 4:3 FREQ 01 2:0 RESOLUTION 000 7 6 5:4 Reserved DOZEEN DOZEPERIOD 0 1 00 3:2 1:0 Reserved RAWFILT 00 00 7:0 AVGTHRESH 0x00 © 2014 Semtech Corporation 30 Defines the digital gain factor: 00: Off (x1) 01: x2 10: x4 11: x8 (Typ.) This is a pure digital gain (value shift) applied at the ADC output. Defines the sampling frequency: 00: 83 kHz 01: 125 kHz 10: 167 kHz (Typ.) 11: Reserved Defines the capacitance measurement resolution/precision: 000: Coarsest …. 100: Medium …. 111: Finest (Typ.) Enables Doze mode. When DOZEN=1, defines the Doze scan period: 00: 2x SCANPERIOD 01: 4x SCANPERIOD 10: 8x SCANPERIOD 11: 16x SCANPERIOD Defines PROXRAW filter strength : 00: Off - No filtering 01: Low (Typ.) 10: Medium 11: High - Max filtering Defines the positive and negative average thresholds which will trigger compensation: Thresholds = +/- 128x AVGTHRESH Typically set between +/-16384 and +/-24576 (i.e. ½ to ¾ of the system dynamic range). www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 0x0B 0x0C 0x0D RegProxCtrl5 RegProxCtrl6 RegProxCtrl7 Revision 4 R/W R/W R/W February 4, 2014 7:6 AVGDEB 00 5:3 AVGNEGFILT 000 2:0 AVGPOSFILT 000 7:5 4:0 Reserved PROXTHRESH 7 AVGCOMPDIS 000 00000 0 © 2014 Semtech Corporation 31 Should not be set below 0x40. Defines the average debouncer applied to AVGTHRESH: 00: Off 01: 2 samples 10: 4 samples 11: 8 samples Defines the average negative filter strength: 000: Off - No filtering 001: Lowest (Typ.) …. 111: Highest - Max filtering Defines the average positive filter strength: 000: Off - No filtering 001: Lowest …. 111: Highest - Max filtering (Typ.) Defines the proximity detection threshold (for all sensors). 00000: 0 00001: 20 00010: 40 00011: 60 00100: 80 00101: 100 00110: 120 00111: 140 01000: 160 01001: 180 01010: 200 01011: 220 01100: 240 01101: 260 01110: 280 01111: 300 10000: 350 10001: 400 10010: 450 10011: 500 10100: 600 10101: 700 10110: 800 10111: 900 11000: 1000 11001: 1100 11010: 1200 11011: 1300 11100: 1400 11101: 1500 11110: 1600 11111: 1700 Low values allow good sensitivity/distance while higher values allow better noise immunity. Disables the automatic compensation triggered by AVGTHRESH. www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 0x0E 0x20 RegProxCtrl8 RegSensorSel 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 RegUseMsb RegUseLsb RegAvgMsb RegAvgLsb RegDiffMsb RegDiffLsb RegOffsetMsb RegOffsetLsb 0x7F RegReset 6 COMPMETHOD 0 5:4 HYST 00 3:2 CLOSEDEB 00 1:0 FARDEB 00 7:4 STUCK 0000 3:0 COMPPRD 0000 R RW 7:2 1:0 Sensor Data Readback Reserved 000000 SENSORSEL 00 R R R R R R R/W R/W 7:0 7:0 7:0 7:0 7:0 7:0 7:0 7:0 W 7:0 R/W PROXUSEFUL PROXAVG PROXDIFF PROXOFFSET 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 Software Reset SOFTRESET 0x00 Defines the compensation method: 0: Compensate each CSx pin independently (Typ.) 1: Compensate all CSx pins together. Defines the proximity detection hysteresis applied to PROXTHRESH: 00: 32 01: 64 10: 128 11: 256 Defines the Close debouncer applied to PROXTHRESH: 00: Off 01: 2 samples 10: 4 samples 11: 8 samples Defines the Far debouncer applied to PROXTHRESH: 00: Off 01: 2 samples 10: 4 samples 11: 8 samples Defines the proximity “stuck” timeout: 0000 : Off (Typ.) 00XX: STUCK x 64 samples 01XX: STUCK x 128 samples 1XXX: STUCK x 256 samples Defines the periodic compensation interval: 0000: Off (Typ.) Else: COMPPRD x 128 samples Defines which sensor’s data will be available in registers RegUseMsb to RegOffsetLsb (addr. 0x21 to 0x28): 00: CS0 01: CS1 10: CS2 11: CS3 Useful current value. Signed, 2's complement format. Average current value. Signed, 2's complement format. Diff current value. Signed, 2's complement format. Compensation offset current value. Unsigned. To force a value, MSB and LSB registers must be written in sequence and change is effective after LSB. Writing 0xDE resets the chip. Table 10: Registers Detailed Description Revision 4 February 4, 2014 © 2014 Semtech Corporation 32 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 9 APPLICATION INFORMATION 9.1 Typical Application Circuit Figure 30: Typical Application Circuit 9.2 External Components Recommended Values Symbol CVDD CSVDD RPULL Description Core supply decoupling capacitor Host interface supply decoupling capacitor Host interface pull-ups Note +/- 50% Min - Typ. 100 100 10 Max - Unit nF nF kΩ Table 11: External Components Recommended Values Revision 4 February 4, 2014 © 2014 Semtech Corporation 33 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 10 PACKAGING INFORMATION 10.1 Outline Drawing Figure 31: Outline Drawing Revision 4 February 4, 2014 © 2014 Semtech Corporation 34 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING 10.2 Land Pattern Figure 32: Land Pattern Revision 4 February 4, 2014 © 2014 Semtech Corporation 35 www.semtech.com SX9500 Ultra Low Power, Four Channels Capacitive Proximity/Button Solution WIRELESS & SENSING © Semtech 2014 All rights reserved. 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