AD7147A datasheet(3/69 Pages) AD

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AD7147A

Rev. B | Page 2 of 68

TABLE OF CONTENTS

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

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

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

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

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

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

Average Current Specifications .................................................. 4

SPI Timing Specifications (AD7147A)...................................... 5

I2C Timing Specifications (AD7147A-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

BIAS Pin....................................................................................... 12

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

Capacitance-to-Digital Converter................................................ 14

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

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

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

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

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

Capacitance Sensor Input Configuration.................................... 17

CINx Input Multiplexer Setup .................................................. 17

Single-Ended Connections to the CDC .................................. 17

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

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

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

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

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

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

Threshold Equations.................................................................. 23

Capacitance Sensor Behavior with Calibration...................... 24

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

ACSHIELD Output .......................................................................... 31

General-Purpose Input/Output (GPIO) ................................. 31

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

Serial Interfaces............................................................................... 32

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

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

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

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

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

WLCSP Package ......................................................................... 37

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

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

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

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

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

Bank 3 Registers ......................................................................... 56

Outline Dimensions ....................................................................... 68

Ordering Guide .......................................................................... 68

REVISION HISTORY

12/09—Rev. A to Rev. B

Changes to Figure 1.......................................................................... 1

Changes to Figure 5, Figure 6, and Pin Description for B2 ........ 8

Changes to Figure 59 and Figure 60............................................. 39

Changes to Ordering Guide .......................................................... 68

3/09—Rev. 0 to Rev. A

Changes to Ordering Guide .......................................................... 68

1/09—Revision 0: Initial Version

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