AD7156

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

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

Capacitance-to-Digital Converter............................................ 11

CAPDAC ..................................................................................... 11

Comparator and Threshold Modes.......................................... 12

Adaptive Threshold.................................................................... 12

Sensitivity..................................................................................... 12

Data Average ............................................................................... 13

Hysteresis..................................................................................... 13

Timeout........................................................................................ 13

Auto-DAC Adjustment.............................................................. 14

Power-Down Timer ................................................................... 14

Register Descriptions ..................................................................... 15

Status Register ............................................................................. 16

Data Registers ............................................................................. 17

Average Registers........................................................................ 18

Fixed Threshold Registers ......................................................... 18

Sensitivity Registers ................................................................... 18

Timeout Registers....................................................................... 18

Setup Registers............................................................................ 19

Configuration Register .............................................................. 20

Power-Down Timer Register .................................................... 21

CAPDAC Registers .................................................................... 21

Serial Number Register.............................................................. 21

Chip ID Register......................................................................... 21

Serial Interface ................................................................................ 22

Read Operation........................................................................... 22

Write Operation.......................................................................... 22

AD7156 Reset ............................................................................. 23

General Call ................................................................................ 23

Hardware Design Considerations ................................................ 24

Overview ..................................................................................... 24

Parasitic Capacitance to Ground.............................................. 24

Parasitic Resistance to Ground................................................. 24

Parasitic Parallel Resistance ...................................................... 24

Parasitic Serial Resistance ......................................................... 25

Input Overvoltage Protection ................................................... 25

Input EMC Protection ............................................................... 25

Power Supply Decoupling and Filtering.................................. 25

Application Examples ................................................................ 26

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

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

REVISION HISTORY

10/08—Revision 0: Initial Version