AD7747

Rev. 0 | Page 2 of 28

TABLE OF CONTENTS

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

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

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

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

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

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

Timing Specifications .................................................................. 5

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

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

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

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

Output Noise and Resolution Specifications .............................. 11

Serial Interface ................................................................................ 12

Read Operation........................................................................... 12

Write Operation.......................................................................... 12

AD7747 Reset.............................................................................. 13

General Call................................................................................. 13

Register Descriptions ..................................................................... 14

Status Register ............................................................................. 15

Cap Data Register....................................................................... 15

VT Data Register ........................................................................ 15

Cap Setup Register ..................................................................... 16

VT Setup Register....................................................................... 16

EXC Setup Register .................................................................... 17

Configuration Register .............................................................. 18

Cap DAC A Register .................................................................. 19

Cap DAC B Register................................................................... 19

Cap Offset Calibration Register ............................................... 20

Cap Gain Calibration Register.................................................. 20

Volt Gain Calibration Register ................................................. 20

Circuit Description......................................................................... 21

Overview ..................................................................................... 21

Capacitance-to-Digital Converter............................................ 21

Active AC Shield Concept......................................................... 21

CAPDAC ..................................................................................... 21

Single-Ended Capacitive Configuration ................................. 22

Differential Capacitive Configuration..................................... 22

Parasitic Capacitance ................................................................. 23

Parasitic Resistance .................................................................... 23

Parasitic Serial Resistance ......................................................... 23

Capacitive Gain Calibration ..................................................... 23

Capacitive System Offset Calibration ...................................... 24

Internal Temperature Sensor .................................................... 24

External Temperature Sensor ................................................... 24

Voltage Input............................................................................... 25

VDD Monitor ................................................................................ 25

Typical Application Diagram.................................................... 26

Outline Dimensions ....................................................................... 27

Ordering Guide .......................................................................... 27

REVISION HISTORY

1/07—Revision 0: Initial Version