Datasheet
AD7707
Rev. B | Page 2 of 52
TABLE OF CONTENTS
Features .............................................................................................. 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Product Highlights ........................................................................... 1
Revision History ............................................................................... 3
Specifications ..................................................................................... 4
Timing Characteristics ................................................................ 8
Absolute Maximum Ratings ............................................................ 9
ESD Caution .................................................................................. 9
Pin Configuration and Function Descriptions ........................... 10
Typical Performance Characteristics ........................................... 12
OVtput Noise .................................................................................. 14
Output Noise For Low Level Input Channels
(5 V Operation) .......................................................................... 14
Output Noise For Low Level Input Channels
(3 V Operation) .......................................................................... 15
Output Noise For High Level Input Channel AIN3
(5 V Operation) .......................................................................... 16
Output Noise For High Level Input Channel AIN3
(3 V Operation) .......................................................................... 17
On-Chip Registers .......................................................................... 18
Communications Register (RS2, RS1, RS0 = 0, 0, 0) ............. 18
Calibration Sequences .................................................................... 23
Circuit Description ......................................................................... 24
Analog Input ................................................................................... 25
Analog Input Ranges .................................................................. 25
Input Sample Rate ...................................................................... 26
Bipolar/Unipolar Inputs ............................................................ 26
Reference Input ............................................................................... 27
Digital Filtering ............................................................................... 28
Filter Characteristics .................................................................. 28
Postfiltering ................................................................................. 29
Analog Filtering .......................................................................... 29
Calibration ....................................................................................... 30
Self-Calibration ........................................................................... 30
System Calibration ..................................................................... 30
Span and Offset Limits on the Low Level Input Channels,
AIN1 and AIN2 .......................................................................... 31
Span and Offset Limits on the High Level Input Channel
AIN3 ............................................................................................. 31
Power-Up and Calibration ........................................................ 32
Using the AD7707 .......................................................................... 33
Clocking and Oscillator Circuit ............................................... 33
System Synchronization ............................................................ 33
Reset Input .................................................................................. 34
Standby Mode ............................................................................. 34
Accuracy ...................................................................................... 34
Drift Considerations .................................................................. 34
Power Supplies ................................................................................ 35
Supply Current ............................................................................ 35
Grounding and Layout .............................................................. 35
Digital Interface .............................................................................. 36
Configuring the AD7707 ............................................................... 37
Microcomputer/Microprocessor Interfacing .............................. 39
AD7707to68HC11 Interface .................................................. 39
AD7707to8XC51 Interface ..................................................... 40
Code For Setting Up the AD7707 ................................................ 41
C Code for Interfacing AD7707 to 68HC11 ........................... 41
Applications Information .............................................................. 43
Data Acquisition ......................................................................... 43
Smart Valve/Actuator Control .................................................. 43
Pressure Measurement ............................................................... 45
Thermocouple Measurement ................................................... 45
RTD Measurement ..................................................................... 45
Chart Recorders .......................................................................... 46
Accommodating Various High Level Input Ranges .............. 46
Typical Input Currents ............................................................... 46
Output Noise For High Level Input Channel, AIN3 ................. 47
5 V Operation ............................................................................. 47
3 V Operation ............................................................................. 48
Outline Dimensions ....................................................................... 49
Ordering Guide .......................................................................... 50