AD7142 datasheet(2/70 Pages) AD

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AD7142

Data Sheet

Rev. B | Page 2 of 70

TABLE OF CONTENTS

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

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

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

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

Revision History ............................................................................... 3

Specifications..................................................................................... 4

SPI Timing Specifications (AD7142)......................................... 6

I2C Timing Specifications (AD7142-1) ..................................... 7

Absolute Maximum Ratings............................................................ 8

ESD Caution.................................................................................. 8

Pin Configurations and Function Descriptions ........................... 9

Typical Performance Characteristics ........................................... 10

Theory of Operation ...................................................................... 12

Capacitance Sensing Theory..................................................... 12

Operating Modes........................................................................ 13

Capacitance Sensor Input Configuration.................................... 14

CIN Input Multiplexer Setup.................................................... 14

Capacitance-to-Digital Converter................................................ 15

Oversampling the CDC Output ............................................... 15

Capacitance Sensor Offset Control.......................................... 15

Conversion Sequencer ............................................................... 15

CDC Conversion Sequence Time ............................................ 16

CDC Conversion Results........................................................... 17

Noncontact Proximity Detection ................................................. 18

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

Proximity Sensitivity.................................................................. 18

FF_SKIP_CNT............................................................................ 21

Environmental Calibration ........................................................... 23

Capacitance Sensor Behavior Without Calibration............... 23

Capacitance Sensor Behavior with Calibration...................... 23

Slow FIFO.................................................................................... 24

SLOW_FILTER_UPDATE_LVL.............................................. 24

Adaptive Threshold and Sensitivity ............................................. 25

Interrupt Output............................................................................. 27

CDC Conversion Complete Interrupt..................................... 27

Sensor Touch Interrupt.............................................................. 27

GPIO INT Output Control ....................................................... 29

Outputs ............................................................................................ 31

Excitation Source........................................................................ 31

CSHIELD Output ............................................................................. 31

GPIO ............................................................................................ 31

Using the GPIO to Turn On/Off an LED................................ 31

Serial Interface ................................................................................ 32

SPI Interface................................................................................ 32

I2C Compatible Interface........................................................... 34

VDRIVE Input ................................................................................. 36

PCB Design Guidelines ................................................................. 37

Capacitive Sensor Board Mechanical Specifications............. 37

Chip Scale Packages ................................................................... 37

Power-Up Sequence ....................................................................... 38

Typical Application Circuits ......................................................... 39

Detailed Register Descriptions ..................................................... 41

Bank 1 Registers ......................................................................... 41

Bank 2 Registers ......................................................................... 51

Bank 3 Registers ......................................................................... 58

Outline Dimensions....................................................................... 70

Ordering Guide .......................................................................... 70

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