Programmable Controller for Capacitance Touch Sensors AD7143 FEATURES FUNCTIONAL BLOCK DIAGRAM Programmable capacitance-to-digital converter POWER-ON 25 ms update rate ( maximum sequence length) RESET AD7143 15 CIN0 LOGIC Better than 1 fF resolution CIN1 16 8 capacitance sensor input channels CIN2 1 16-BIT CALIBRA- CIN3 2 No external RC tuning components required - TION CIN4 3 CDC ENGINE Automatic conversion sequencer CIN5 4 On-chip automatic calibration logic CIN6 5 CALIBRA- 9 VCC Automatic compensation for environmental changes TION CIN7 6 CONTROL RAM 10 GND AND Automatic adaptive threshold and sensitivity levels DATA REGISTERS On-chip RAM to store calibration data 2 I C-compatible serial interface 7 250kHz CSHIELD Separate VDRIVE level for serial interface EXCITATION SRC 8 SOURCE Interrupt output for host controller 16-lead, 4 mm x 4 mm LFCSP-VQ INTERRUPT 2 I C SERIAL INTERFACE LOGIC AND CONTROL LOGIC 2.6 V to 3.6 V supply voltage Low operating current 11 12 13 14 Full power mode: less than 1 mA VDRIVE SDA SCLK INT Low power mode: 50 A Figure 1. APPLICATIONS Personal music and multimedia players Cell phones Digital still cameras Smart hand-held devices Television, A/V, and remote controls Gaming consoles The AD7143 has on-chip calibration logic to account for GENERAL DESCRIPTION changes in the ambient environment. The calibration sequence is The AD7143 is an integrated capacitance-to-digital converter performed automatically and at continuous intervals, while the (CDC) with on-chip environmental calibration for use in sensors are not touched. This ensures that there are no false or systems requiring a novel user input method. The AD7143 nonregistering touches on the external sensors due to a interfaces to external capacitance sensors implementing changing environment. functions, such as capacitive buttons, scroll bars, and 2 The AD7143 has an I C-compatible serial interface and a scroll wheels. 2 separate VDRIVE pin for I C serial interface operating voltages The CDC has eight inputs channeled through a switch matrix to between 1.65 V and 3.6 V. a 16-bit, 250 kHz sigma-delta (-) capacitance-to-digital The AD7143 is available in a 16-lead, 4 mm 4 mm LFCSP-VQ converter. The CDC is capable of sensing changes in the and operates from a 2.6 V to 3.6 V supply. The operating capacitance of the external sensors and uses this information to current consumption is less than 1 mA, falling to 50 A in low register a sensor activation. The external sensors can be power mode (conversion interval of 400 ms). arranged as a series of buttons, as a scroll bar or wheel, or as a combination of sensor types. By programming the registers, the user has full control over the CDC setup. High resolution sensors require software to run on the host processor. Rev. 0 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 www.analog.com license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Fax: 781.461.3113 2007 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. SWITCH MATRIX 06472-001AD7143 TABLE OF CONTENTS Features .............................................................................................. 1 Proximity Sensitivity.................................................................. 17 Applications....................................................................................... 1 Slow FIFO.................................................................................... 19 Functional Block Diagram .............................................................. 1 SLOW FILTER UPDATE LVL .............................................. 19 General Description ......................................................................... 1 Environmental Calibration ........................................................... 22 Revision History ............................................................................... 2 Capacitance Sensor Behavior without Calibration................ 22 Specifications..................................................................................... 3 Capacitance Sensor Behavior with Calibration...................... 23 2 I C Timing Specifications............................................................ 5 Adaptive Threshold and Sensitivity ............................................. 25 Absolute Maximum Ratings............................................................ 6 Interrupt Output............................................................................. 26 ESD Caution.................................................................................. 6 CDC Conversion Complete Interrupt..................................... 26 Pin Configurations and Function Descriptions ........................... 7 Sensor Touch Interrupt.............................................................. 26 Typical Performance Characteristics ............................................. 8 Serial Interface ................................................................................ 28 2 Theory of Operation ...................................................................... 11 I C Compatible Interface........................................................... 28 Capacitance Sensing Theory..................................................... 11 PCB Design Guidelines ................................................................. 31 Operating Modes........................................................................ 12 Capacitive Sensor Board Mechanical Specifications ............. 31 Capacitance Sensor Input Configuration.................................... 13 Chip Scale Packages ................................................................... 31 CIN Input Multiplexer Setup .................................................... 13 Power-Up Sequence ....................................................................... 32 Capacitiance-to-Digital Converter............................................... 14 Typical Application Circuits ......................................................... 33 Oversampling the CDC Output ............................................... 14 Register Map ................................................................................... 34 Capacitance Sensor Offset Control.......................................... 14 Detailed Register Descriptions ..................................................... 35 Conversion Sequencer ............................................................... 14 Bank 1 Registers ......................................................................... 35 CDC Conversion Sequence Time ............................................ 15 Bank 2 Registers ......................................................................... 43 CDC Conversion Results........................................................... 16 Bank 3 Registers ......................................................................... 47 Noncontact Proximity Detection ................................................. 17 Outline Dimensions ....................................................................... 55 Recalibration ............................................................................... 17 Ordering Guide .......................................................................... 55 REVISION HISTORY 1/07Revision 0: Initial Version Rev. 0 Page 2 of 56