Programmable Controller for Capacitance Touch Sensors Data Sheet AD7142 FEATURES FUNCTIONAL BLOCK DIAGRAM V V REF REF+ TEST Programmable capacitance-to-digital converter 29 28 27 36 ms update rate (at maximum sequence length) 30 CIN0 POWER-ON RESET Better than 1 fF resolution 31 CIN1 LOGIC CIN2 32 14 capacitance sensor input channels CIN3 1 AV 13 CC No external RC tuning components required CIN4 2 CIN5 3 AGND 14 Automatic conversion sequencer 4 CIN6 16-BIT CALIBRATION - ENGINE CIN7 5 On-chip automatic calibration logic CDC CIN8 6 Automatic compensation for environmental changes CIN9 7 17 DV CC CIN10 8 Automatic adaptive threshold and sensitivity levels CALIBRATION 18 DGND1 CIN11 9 RAM On-chip RAM to store calibration data CIN12 10 19 DGND2 11 CONTROL CIN13 SPI-compatible serial interface (AD7142) AND DATA 2 I C-compatible serial interface (AD7142-1) REGISTERS Separate V level for serial interface DRIVE C 12 SHIELD Interrupt output and GPIO 250kHz 15 EXCITATION SRC 32-lead, 5 mm x 5 mm LFCSP SOURCE 16 2.6 V to 3.6 V supply voltage SRC Low operating current INTERRUPT SERIAL INTERFACE V AND GPIO DRIVE 20 26 GPIO Full power mode: less than 1 mA AND CONTROL LOGIC LOGIC Low power mode: 50 A 21 22 23 24 25 SDO/ SDI/ CS/ SCLK INT APPLICATIONS SDA ADD0 ADD1 Figure 1. Personal music and multimedia players Cell phones Digital still cameras Smart hand-held devices Television, A/V, and remote controls Gaming consoles GENERAL DESCRIPTION The AD7142 and AD7142-1 have on-chip calibration logic to The AD7142 and AD7142-1 are integrated capacitance-to- account for changes in the ambient environment. The digital converters (CDCs) with on-chip environmental calibration sequence is performed automatically and at calibration for use in systems requiring a novel user input continuous intervals, when the sensors are not touched. This method. The AD7142 and AD7142-1 can interface to external ensures that there are no false or nonregistering touches on the capacitance sensors implementing functions such as capacitive external sensors due to a changing environment. buttons, scroll bars, or wheels. The AD7142 has an SPI-compatible serial interface, and the The CDC has 14 inputs channeled through a switch matrix to a 2 AD7142-1 has an I C-compatible serial interface. Both parts 16-bit, 250 kHz sigma-delta (-) capacitance -to-digital have an interrupt output, as well as a general-purpose input/ converter. The CDC is capable of sensing changes in the output (GPIO). capacitance of the external sensors and uses this information to register a sensor activation. The external sensors can be The AD7142 and AD7142-1 are available in a 32-lead, 5 mm arranged as a series of buttons, as a scroll bar or wheel, or as a 5 mm LFCSP and operate from a 2.6 V to 3.6 V supply. The combination of sensor types. By programming the registers, the operating current consumption is less than 1 mA, falling to user has full control over the CDC setup. High resolution 50 A in low power mode (conversion interval of 400 ms). sensors require minor software to run on the host processor. Rev. B Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. rights of third parties that may result from its use. Specifications subject to change without notice. No Tel: 781.329.4700 20062017 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. Technical Support www.analog.com SWITCH MATRIX 05702-001AD7142 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Capacitance Sensor Behavior with Calibration ...................... 23 Applications ....................................................................................... 1 Slow FIFO .................................................................................... 24 Functional Block Diagram .............................................................. 1 SLOW FILTER UPDATE LVL .............................................. 24 General Description ......................................................................... 1 Adaptive Threshold and Sensitivity ............................................. 25 Revision History ............................................................................... 3 Interrupt Output ............................................................................. 27 Specifications ..................................................................................... 4 CDC Conversion Complete Interrupt ..................................... 27 SPI Timing Specifications (AD7142) ......................................... 6 Sensor Touch Interrupt.............................................................. 27 2 I C Timing Specifications (AD7142-1) ..................................... 7 GPIO INT Output Control ....................................................... 29 Absolute Maximum Ratings ............................................................ 8 Outputs ............................................................................................ 31 ESD Caution .................................................................................. 8 Excitation Source ........................................................................ 31 Pin Configurations and Function Descriptions ........................... 9 CSHIELD Output ............................................................................. 31 Typical Performance Characteristics ........................................... 10 GPIO ............................................................................................ 31 Theory of Operation ...................................................................... 12 Using the GPIO to Turn On/Off an LED ................................ 31 Capacitance Sensing Theory ..................................................... 12 Serial Interface ................................................................................ 32 Operating Modes ........................................................................ 13 SPI Interface ................................................................................ 32 2 Capacitance Sensor Input Configuration .................................... 14 I C Compatible Interface ........................................................... 34 CIN Input Multiplexer Setup .................................................... 14 VDRIVE Input ................................................................................. 36 Capacitance-to-Digital Converter ................................................ 15 PCB Design Guidelines ................................................................. 37 Oversampling the CDC Output ............................................... 15 Capacitive Sensor Board Mechanical Specifications ............. 37 Capacitance Sensor Offset Control .......................................... 15 Chip Scale Packages ................................................................... 37 Conversion Sequencer ............................................................... 15 Power-Up Sequence ....................................................................... 38 CDC Conversion Sequence Time ............................................ 16 Typical Application Circuits ......................................................... 39 CDC Conversion Results ........................................................... 17 Register Map ................................................................................... 40 Noncontact Proximity Detection ................................................. 18 Detailed Register Descriptions ..................................................... 41 Recalibration ............................................................................... 18 Bank 1 Registers ......................................................................... 41 Proximity Sensitivity .................................................................. 18 Bank 2 Registers ......................................................................... 51 FF SKIP CNT ............................................................................ 21 Bank 3 Registers ......................................................................... 58 Environmental Calibration ........................................................... 23 Outline Dimensions ....................................................................... 70 Capacitance Sensor Behavior Without Calibration ............... 23 Ordering Guide .......................................................................... 70 Rev. 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