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AD7148

Rev. 0 | Page 2 of 56

TABLE OF CONTENTS

Features .............................................................................................. 1

Applications....................................................................................... 1

General Description ......................................................................... 1

Functional Block Diagram .............................................................. 1

Revision History ............................................................................... 2

Specifications..................................................................................... 3

Typical Average Current in Low Power Mode ......................... 4

Maximum Average Current in Low Power Mode.................... 4

I2C Timing Specifications (AD7148-1) ..................................... 5

Absolute Maximum Ratings............................................................ 6

ESD Caution.................................................................................. 6

Pin Configuration and Function Descriptions............................. 7

Typical Performance Characteristics ............................................. 8

Theory of Operation ...................................................................... 10

Capacitance Sensing Theory..................................................... 10

BIAS Pin....................................................................................... 11

Operating Modes........................................................................ 11

Capacitance-to-Digital Converter................................................ 13

Oversampling the CDC Output ............................................... 13

Capacitance Sensor Offset Control.......................................... 13

Conversion Sequencer ............................................................... 13

CDC Conversion Sequence Time ............................................ 14

CDC Conversion Results........................................................... 15

Capacitance Sensor Input Configuration.................................... 16

CINx Input Multiplexer Setup .................................................. 16

Single-Ended Connections to the CDC .................................. 16

Noncontact Proximity Detection ................................................. 17

Recalibration ............................................................................... 18

Proximity Sensitivity.................................................................. 20

FF_SKIP_CNT............................................................................ 20

Environmental Calibration ........................................................... 22

Capacitance Sensor Behavior Without Calibration............... 22

Capacitance Sensor Behavior with Calibration...................... 22

SLOW FIFO ................................................................................ 23

SLOW_FILTER_UPDATE_LVL .............................................. 23

Adaptive Threshold and Sensitivity ............................................. 24

Interrupt Output............................................................................. 26

CDC Conversion-Complete Interrupt .................................... 26

Sensor Touch Interrupt.............................................................. 26

ACSHIELD Output .............................................................................. 27

I2C-Compatible Serial Interface ................................................... 28

VDRIVE Input ................................................................................. 30

PCB Design Guidelines ................................................................. 31

Capacitive Sensor Board Mechanical Specifications ............. 31

Chip Scale Packages ................................................................... 31

Power-Up Sequence ....................................................................... 32

Typical Application Circuit ........................................................... 33

Detailed Register Descriptions ..................................................... 35

Bank 1 Registers ......................................................................... 35

Bank 2 Registers ......................................................................... 43

Bank 3 Registers ......................................................................... 48

Outline Dimensions ....................................................................... 56

Ordering Guide .......................................................................... 56

REVISION HISTORY

12/07—Revision 0: Initial Version

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