CapTouch Programmable Controller for Single-Electrode Capacitance Sensors Data Sheet AD7147 FEATURES FUNCTIONAL BLOCK DIAGRAM AC V GND BIAS SHIELD CC Programmable capacitance-to-digital converter (CDC) 8 11 10 9 Femtofarad resolution 13 capacitance sensor inputs POWER-ON CIN0 19 RESET LOGIC 9 ms update rate, all 13 sensor inputs 20 CIN1 No external RC components required 21 CIN2 EXCITATION Automatic conversion sequencer SOURCE CIN3 22 On-chip automatic calibration logic 23 CIN4 Automatic compensation for environmental changes CIN5 24 CALIBRATION AD7147/ Automatic adaptive threshold and sensitivity levels RAM 1 AD7147-1 CIN6 Register map is compatible with the AD7142 2 CIN7 On-chip RAM to store calibration data CIN8 3 16-BIT CALIBRATION SPI-compatible (serial-peripheral-interface-compatible) - ENGINE 4 CDC CIN9 serial interface (AD7147) 5 2 CIN10 I C-compatible serial interface (AD7147-1) CIN11 6 CONTROL Separate V level for serial interface DRIVE AND DATA 7 CIN12 REGISTERS Interrupt output and general-purpose input/output (GPIO) 24-lead, 4 mm 4 mm LFCSP 2.6 V to 3.3 V supply voltage Low operating current INTERRUPT SERIAL INTERFACE 12 18 V AND GPIO GPIO DRIVE AND CONTROL LOGIC Full power mode: 1 mA LOGIC Low power mode: 21.5 A 13 14 15 16 17 Qualified for automotive applications SDO/ SDI/ SCLK CS/ INT SDA ADD0 ADD1 APPLICATIONS Figure 1. Cell phones Personal music and multimedia players The AD7147 is designed for single electrode capacitance sensors Smart handheld devices (grounded sensors). There is an active shield output to Television, A/V, and remote controls minimize noise pickup in the sensor. Gaming consoles Digital still cameras The AD7147 has on-chip calibration logic to compensate for changes in the ambient environment. The calibration sequence GENERAL DESCRIPTION is performed automatically and at continuous intervals as long The AD7147 CapTouch controller is designed for use with as the sensors are not touched. This ensures that there are no capacitance sensors implementing functions such as buttons, false or nonregistering touches on the external sensors due to scroll bars, and wheels. The sensors need only one PCB layer, a changing environment. enabling ultrathin applications. The AD7147 has an SPI-compatible serial interface, and the The AD7147 is an integrated CDC with on-chip environmental 2 AD7147-1 has an I C-compatible serial interface. Both parts have calibration. The CDC has 13 inputs channeled through a switch an interrupt output, as well as a GPIO. There is a V pin to set DRIVE matrix to a 16-bit, 250 kHz sigma-delta (-) converter. The CDC the voltage level for the serial interface independent of V . CC is capable of sensing changes in the capacitance of the external The AD7147 is available in a 24-lead, 4 mm 4 mm LFCSP and sensors and uses this information to register a sensor activation. operates from a 2.6 V to 3.6 V supply. The operating current con- By programming the registers, the user has full control over the sumption in low power mode is typically 26 A for 13 sensors. CDC setup. High resolution sensors require minor software to run on the host processor. Rev. 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SWITCH MATRIX 06663-001AD7147 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Capacitance Sensor Behavior Without Calibration ............... 24 Applications ....................................................................................... 1 Threshold Equations .................................................................. 25 General Description ......................................................................... 1 Capacitance Sensor Behavior with Calibration ...................... 25 Functional Block Diagram .............................................................. 1 Slow FIFO .................................................................................... 25 Revision History ............................................................................... 3 SLOW FILTER UPDATE LVL .............................................. 26 Specifications ..................................................................................... 4 Adaptive Threshold and Sensitivity ............................................. 27 Average Current Specifications .................................................. 5 Interrupt Output ............................................................................. 29 SPI Timing Specifications (AD7147) ......................................... 6 CDC Conversion-Complete Interrupt .................................... 29 2 I C Timing Specifications (AD7147-1) ...................................... 7 Sensor-Touch Interrupt ............................................................. 29 Absolute Maximum Ratings ............................................................ 8 GPIO INT Output Control ....................................................... 31 ESD Caution .................................................................................. 8 Outputs ............................................................................................ 33 Pin Configurations and Function Descriptions ........................... 9 AC Output .......................................................................... 33 SHIELD Typical Performance Characteristics ........................................... 10 General-Purpose Input/Output (GPIO) ................................. 33 Theory of Operation ...................................................................... 12 Using the GPIO to Turn On/Off an LED ................................ 33 Capacitance Sensing Theory ..................................................... 12 Serial Interface ................................................................................ 34 BIAS Pin ....................................................................................... 13 SPI Interface ................................................................................ 34 2 Operating Modes ........................................................................ 13 I C-Compatible Interface .......................................................... 36 Capacitiance-to-Digital Converter ............................................... 15 VDRIVE Input ................................................................................. 38 Oversampling the CDC Output ............................................... 15 PCB Design Guidelines ................................................................. 39 Capacitance Sensor Offset Control .......................................... 15 Capacitive Sensor Board Mechanical Specifications ............. 39 Conversion Sequencer ............................................................... 15 Chip Scale Packages ................................................................... 39 CDC Conversion Sequence Time ............................................ 17 Power-Up Sequence ....................................................................... 40 CDC Conversion Results ........................................................... 17 Typical Application Circuits ......................................................... 41 Capacitance Sensor Input Configuration .................................... 18 Register Map ................................................................................... 42 CINx Input Multiplexer Setup .................................................. 18 Detailed Register Descriptions ..................................................... 43 Single-Ended Connections to the CDC .................................. 18 Bank 1 Registers ......................................................................... 43 Noncontact Proximity Detection ................................................. 19 Bank 2 Registers ......................................................................... 53 Recalibration ............................................................................... 19 Bank 3 Registers ......................................................................... 58 Proximity Sensitivity .................................................................. 19 Outline Dimensions ....................................................................... 70 FF SKIP CNT ............................................................................ 22 Ordering Guide .......................................................................... 70 Environmental Calibration ........................................................... 24 Automotive Products ................................................................. 70 Rev. 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