AD7705/AD7706
TABLE OF CONTENTS
Features .............................................................................................. 1
Reference Input........................................................................... 23
Digital Filtering........................................................................... 23
Analog Filtering.......................................................................... 25
Calibration................................................................................... 25
Theory of Operation ...................................................................... 28
Clocking and Oscillator Circuit ............................................... 28
System Synchronization ............................................................ 28
General Description......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 3
Product Highlights ........................................................................... 4
Specifications..................................................................................... 5
Timing Characteristics ................................................................ 8
Absolute Maximum Ratings............................................................ 9
ESD Caution.................................................................................. 9
Pin Configurations and Function Descriptions ......................... 10
Output Noise (5 V Operation)...................................................... 12
Output Noise (3 V Operation)...................................................... 13
Typical Performance Characteristics ........................................... 14
On-Chip Registers.......................................................................... 16
Communication Register (RS2, RS1, RS0 = 0, 0, 0)............... 16
RESET
Input ............................................................................... 29
Standby Mode ............................................................................. 29
Accuracy...................................................................................... 29
Drift Considerations.................................................................. 29
Power Supplies............................................................................ 30
Supply Current............................................................................ 30
Grounding and Layout .............................................................. 30
Evaluating the Performance...................................................... 31
Digital Interface.......................................................................... 31
Configuring the AD7705/AD7706 .......................................... 33
Microcomputer/Microprocessor Interfacing ......................... 34
Code For Setting Up the AD7705/AD7706............................ 35
Applications..................................................................................... 38
Pressure Measurement............................................................... 38
Temperature Measurement....................................................... 39
Smart Transmitters..................................................................... 40
Battery Monitoring .................................................................... 41
Outline Dimensions....................................................................... 42
Ordering Guide .......................................................................... 43
Setup Register (RS2, RS1, RS0 = 0, 0, 1); Power-On/Reset
Status: 01 Hexadecimal.............................................................. 17
Clock Register (RS2, RS1, RS0 = 0, 1, 0); Power-On/Reset
Status: 05 Hexadecimal.............................................................. 19
Data Register (RS2, RS1, RS0 = 0, 1, 1) ................................... 20
Test Register (RS2, RS1, RS0 = 1, 0, 0); Power-On/Reset
Status: 00 Hexadecimal.............................................................. 20
Zero-Scale Calibration Register (RS2, RS1, RS0 = 1, 1, 0);
Power-On/Reset Status: 1F4000 Hexadecimal........................... 20
Full-Scale Calibration Register (RS2, RS1, RS0 = 1, 1, 1);
Power-On/Reset Status: 5761AB HexaDecimal......................... 20
Circuit Description......................................................................... 21
Analog Input ............................................................................... 22
Bipolar/Unipolar Input.............................................................. 22
Rev. C | Page 2 of 44
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