TIDU858C
March 2015 – May 2021
Description
Resources
Features
Applications
5
1
System Description
1.1
Binary Inputs or Digital Inputs
1.1.1
Binary Input Application Functionality
Common Specifications
1.2
Approaches to Binary Input Module Design
1.2.1
ADC Versus MCU Based Binary Input Module (BIM)
1.3
Measurement of Wide Inputs With Programmable Thresholds
2
Design Features
2.1
Electrical Specifications
2.2
Block Diagram
2.2.1
Analog-to-Digital Converter (ADC)
2.2.1.1
ADS795x SAR ADC Family
2.2.2
Protection and Signal Conditioning
2.2.3
Digital Isolator
2.2.3.1
Host (SPI) Interfacing Using the ISO6741
2.2.4
DC Power Supply Isolator
2.2.5
Design Alternative: ADC With Digitally Programmable Threshold
2.2.5.1
ADS7128 SAR ADC With Programmable Threshold
2.2.5.2
I2C Interfacing Using the ISO1640 and Optional Altert Interface Using ISO7710
3
Circuit Design and Component Selection
3.1
Analog-to-Digital Converter (ADC)
3.2
Input Signal Conditioning
3.2.1
Voltage Divider
3.2.2
TLV6002 Operational Amplifier
3.3
Isolated Interface
3.4
Isolated DC Power Supply
3.4.1
Reinforced Power Isolator: UCC12050 High-Efficiency 500-mW DC/DC Converter
3.5
Enhancements
4
Testing
4.1
Test Setup and Connection Diagram
4.2
Test Data
4.2.1
Voltage Measurement Accuracy Testing
4.3
Test Results Summary
5
Design Files
5.1
Schematics
5.2
Bill of Materials
5.3
Altium Project
5.4
Gerber Files
6
References
Trademarks
7
About the Author
8
Revision History
Features
Scalable input AC/DC binary input module with ADC front end
ADS795x product family supports 4, 8, 12, or 16 channels in different packages
ADS7128 product family support programmable threshold setting using internal digital comparator
Digital isolator based interface isolation
Isolated DC/DC based power supply to isolate the host from the sensor side
Improved system reliability from use of digital isolators over optocoupler based solution
Wide input range from 10 V to 300 V and supports measurement in AC or DC input voltages
Measurement of input voltage provides provision for programmable threshold
Device selection optimized for low-cost per channel