AD7142 datasheet(2/68 Pages) AD

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AD7142

Rev. 0 | Page 2 of 68

TABLE OF CONTENTS

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

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

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

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

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

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

SPI Timing Specifications (AD7142)......................................... 5

I2C Timing Specifications (AD7142-1) ..................................... 6

Absolute Maximum Ratings............................................................ 7

ESD Caution.................................................................................. 7

Pin Configurations and Function Descriptions ........................... 8

Typical Performance Characteristics ............................................. 9

Theory of Operation ...................................................................... 11

Capacitance Sensing Theory..................................................... 11

Operating Modes........................................................................ 12

Capacitance Sensor Input Configuration.................................... 13

CIN Input Multiplexer Setup .................................................... 13

Capacitiance-to-Digital Converter............................................... 14

Oversampling the CDC Output ............................................... 14

Capacitance Sensor Offset Control.......................................... 14

Conversion Sequencer ............................................................... 14

CDC Conversion Sequence Time ............................................ 15

CDC Conversion Results........................................................... 16

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

Recalibration ............................................................................... 17

Proximity Sensitivity .................................................................. 17

FIFO Control .............................................................................. 20

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

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

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

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

Interrupt Output............................................................................. 25

CDC Conversion Complete Interrupt..................................... 25

Sensor Touch Interrupt.............................................................. 25

GPIO INT Output Control ....................................................... 27

Outputs ............................................................................................ 29

Excitation Source........................................................................ 29

CSHIELD Output ............................................................................. 29

GPIO ............................................................................................ 29

Using the GPIO to turn on/off an LED................................... 29

Serial Interface ................................................................................ 30

SPI Interface ................................................................................ 30

I2C Compatible Interface........................................................... 32

VDRIVE Input ................................................................................. 34

PCB Design Guidelines ................................................................. 35

Capacitive Sensor Board Mechanical Specifications ............. 35

Chip Scale Packages ................................................................... 35

Power-Up Sequence ....................................................................... 36

Typical Application Circuits ......................................................... 37

Detailed Register Descriptions ..................................................... 39

Bank 1 Registers ......................................................................... 39

Bank 2 Registers ......................................................................... 48

Bank 3 Registers ......................................................................... 54

Outline Dimensions ....................................................................... 66

Ordering Guide .......................................................................... 66

REVISION HISTORY

6/06—Revision 0: Initial Version

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