SDAA162 July   2026 ADS125H18 , ISO7721 , ISO7730 , ISO7731 , SN6505B , SN74LVC1G17 , TUSB320 , TVS3301

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Design Overview and Measurement Performance (Normal Operation)
    1. 1.1 Design Overview
    2. 1.2 EMC Test Board Voltage Measurement Performance During Normal Operation
    3. 1.3 EMC Test Board Current Measurement Performance During Normal Operation
  5. 2EMC Test Board Circuit and PCB Layout Considerations
    1. 2.1 Circuit Design Considerations for EMC Compliance
      1. 2.1.1 High-Voltage Capacitors and Resistors on Every Input Connector Pin
      2. 2.1.2 TVS Diodes
      3. 2.1.3 Protecting the Current Shunt: PTC and Zener Diodes
      4. 2.1.4 Series Resistors on Digital Signals
      5. 2.1.5 Digital Isolation
      6. 2.1.6 Power Supply and Protection
      7. 2.1.7 High-Voltage Capacitors and Resistors for Discharging Path
    2. 2.2 PCB Layout Considerations for EMC Compliance
      1. 2.2.1 PCB Layer Stack-up and Ground Plane
      2. 2.2.2 Avoiding a Long Return Path
      3. 2.2.3 Avoiding 90-Degree Bends in PCB Traces
      4. 2.2.4 Using a Guard Ring to Isolate Interference Signals
      5. 2.2.5 Decoupling Capacitors
      6. 2.2.6 Differential Signal Routing
      7. 2.2.7 Stitching Vias
      8. 2.2.8 Layout for Isolation Barrier
      9. 2.2.9 Component Placement
  6. 3EMC Test System, Standards, and Results
    1. 3.1 EMC Test System
    2. 3.2 EMC Test Standards
    3. 3.3 EMC Test Results
      1. 3.3.1 Electrostatic Discharge (ESD)
      2. 3.3.2 Radiated Immunity (RI)
      3. 3.3.3 Electrical Fast Transients (EFT)
      4. 3.3.4 Surge Immunity (SI)
      5. 3.3.5 Conducted Immunity (CI)
  7. 4Schematic, PCB Layout and Bill of Materials
    1. 4.1 Schematic
    2. 4.2 PCB Layout
    3. 4.3 Bill of Materials (BOM)
  8. 5Summary
  9. 6References

3.1 EMC Test System

Figure 3-1 shows the general setup of the ADS125H18 EMC test board. A software script configures the system parameters including the SPI interface, clock frequency configuration, ADC mode selection, data capture and analysis, data monitoring, and exporting for post-processing. The software and the PHI controller verify the operation of the test system and the equipment under test (EUT) before the EMC test. The system continuously captures and monitors the data during the EMC event and also checks the EUT functionality after the EMC test.

The PHI controller card provides a communication interface between the ADS125H18 EMC test board and the laptop over a USB 2.0 (or higher) interface for digital input and output. The test system uses a battery powered optical transceiver pair between the laptop and the PHI controller card. The optical transceiver pair isolates harsh transient signals from the test environment and provides an additional layer of protection for the user equipment.

Test Hardware

  • ADS125H18 EMC test board
  • PHI controller card from Texas Instruments
  • Optical transceivers with fiber optic cables
  • Twisted-pair wire with a 9V battery for voltage measurements or a precision signal for current measurements
  • Specific equipment for individual EMC test
  • Laptop running Windows® 10 or 11, 64-bit version
  • Lab supply or 9V lead battery for floating system power supply
General EMC Test SetupFigure 3-1 General EMC Test Setup