Programmable Touch Controller for Single Electrode Capacitance Sensors Data Sheet AD7148 FEATURES FUNCTIONAL BLOCK DIAGRAM AC V SHIELD CC GND BIAS Programmable capacitance-to-digital converter (CDC) 5 8 7 6 Femtofarad (fF) resolution AD7148 8 capacitance sensor inputs 13 CIN0 POWER-ON 25 ms update rate, all 8 sensor inputs RESET LOGIC EXCITATION CIN1 14 No external RC components required SOURCE Automatic conversion sequencer CIN2 15 CALIBRATION RAM On-chip automatic calibration logic CIN3 16 Automatic compensation for environmental changes 16-BIT CALIBRATION - Automatic adaptive threshold and sensitivity levels CIN4 1 ENGINE CDC Register map compatible with AD7143 CIN5 2 On-chip RAM to store calibration data CONTROL 2 AND CIN6 3 I C-compatible serial interface DATA REGISTERS Separate V level for serial interface DRIVE 4 CIN7 Interrupt output 16-lead, 4 mm 4 mm LFCSP INTERRUPT 2.6 V to 3.3 V supply voltage SERIAL INTERFACE AND GPIO AND CONTROL LOGIC LOGIC Low operating current Full power mode: 1 mA 9 10 11 12 Low power mode: 21.5 A V DRIVE SDA SCLK INT APPLICATIONS Figure 1. Cell phones Personal music and multimedia players Smart handheld devices Television, A/V, and remote controls Gaming consoles Digital still cameras GENERAL DESCRIPTION The AD7148 is designed for single electrode capacitance sensors The AD7148 is designed for use with capacitance sensors imple- (grounded sensors). There is an active shield output to minimize menting functions such as buttons, scroll bars, and wheels. noise pickup in the sensor. For floating, or two, electrode sensors, The sensors need only one PCB layer, enabling ultrathin use the AD7143. applications. The AD7148 has on-chip calibration logic to compensate for The AD7148 is an integrated capacitance-to-digital converter changes in the ambient environment. The calibration sequence is (CDC) with on-chip environmental calibration. The CDC has eight inputs channeled through a switch matrix to a 16-bit, performed automatically and at continuous intervals as long as the sensors are not touched. This ensures that there are no false 250 kHz sigma-delta (-) converter. The CDC is capable of or nonregistering touches on the external sensors due to a sensing changes in the capacitance of the external sensors and changing environment. uses this information to register a sensor activation. The external sensors can be arranged as a series of buttons, as a scroll bar or 2 The AD7148 has an I C-compatible serial interface, as well as an wheel, or as a combination of sensor types. By programming the interrupt output. There is a V pin to set the voltage level for DRIVE registers, the user has full control over the CDC setup. the serial interface independent of V . CC High resolution sensors require minimal software to run on the The AD7148 is available in a 16-lead, 4 mm 4 mm LFCSP and host processor. operates from a 2.6 V to 3.6 V supply. The operating current consumption in low power mode is typically 26 A. 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 20072015 Analog Devices, Inc. All rights reserved. license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Technical Support www.analog.com Trademarks and registered trademarks are the property of their respective owners. OBSOLETE SWITCH MATRIX 07155-001AD7148 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Proximity Sensitivity .................................................................. 20 Applications ....................................................................................... 1 FF SKIP CNT ............................................................................ 20 General Description ......................................................................... 1 Environmental Calibration ........................................................... 22 Functional Block Diagram .............................................................. 1 Capacitance Sensor Behavior Without Calibration ............... 22 Revision History ............................................................................... 2 Capacitance Sensor Behavior with Calibration ...................... 22 Specif icat ions ..................................................................................... 3 SLOW FIFO ................................................................................ 23 Typical Average Current in Low Power Mode ......................... 4 SLOW FILTER UPDATE LVL .............................................. 23 Maximum Average Current in Low Power Mode .................... 4 Adaptive Threshold and Sensitivity ............................................. 24 2 I C Timing Specifications (AD7148-1) ...................................... 5 Interrupt Output ............................................................................. 26 Absolute Maximum Ratings ............................................................ 6 CDC Conversion-Complete Interrupt .................................... 26 ESD Caution .................................................................................. 6 Sensor Touch Interrupt.............................................................. 26 Pin Configuration and Function Descriptions ............................. 7 ACSHIELD Output .............................................................................. 27 2 Typical Performance Characteristics ............................................. 8 I C-Compatible Serial Interface ................................................... 28 Theory of Operation ...................................................................... 10 V Input ................................................................................. 30 DRIVE Capacitance Sensing Theory ..................................................... 10 PCB Design Guidelines ................................................................. 31 BIAS Pin ....................................................................................... 11 Capacitive Sensor Board Mechanical Specifications ............. 31 Operating Modes ........................................................................ 11 Chip Scale Packages ................................................................... 31 Capacitance-to-Digital Converter ................................................ 13 Power-Up Sequence ....................................................................... 32 Oversampling the CDC Output ............................................... 13 Typical Application Circuit ........................................................... 33 Capacitance Sensor Offset Control .......................................... 13 Register Map ................................................................................... 34 Conversion Sequencer ............................................................... 13 Detailed Register Descriptions ..................................................... 35 CDC Conversion Sequence Time ............................................ 14 Bank 1 Registers ......................................................................... 35 CDC Conversion Results ........................................................... 15 Bank 2 Registers ......................................................................... 43 Capacitance Sensor Input Configuration .................................... 16 Bank 3 Registers ......................................................................... 48 CINx Input Multiplexer Setup .................................................. 16 Outline Dimensions ....................................................................... 56 Single-Ended Connections to the CDC .................................. 16 Ordering Guide .......................................................................... 56 Noncontact Proximity Detection ................................................. 17 Recalibration ............................................................................... 18 REVISION HISTORY 5/15Rev. A to Rev. B Changes to Table 15 ....................................................................... 28 Changes to Figure 4 .......................................................................... 7 Changes to Figure 45 ...................................................................... 33 Updated Outline Dimensions ....................................................... 56 Added Exposed Pad Notation to Outline Dimensions ............. 56 Changes to Ordering Guide .......................................................... 56 12/07Revision 0: Initial Version 1/10Rev. 0 to Rev. A Changes to Figure 4 and Table 6 ..................................................... 7 Changes to BIAS Pin Section ........................................................ 11 Rev. B Page 2 of 56 OBSOLETE