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

3.3.5 Conducted Immunity (CI)

The IEC 61000-4-6 standard specifies the details for the CI test including test criteria and setup requirements. The IEC61000-4-6 test determines the EUT immunity to external conducted electromagnetic disturbances during operation. Figure 3-14 shows that the test signal is generated from an RF signal generator and an RF power amplifier that is used to amplify the test signal to a specified level. The test signal is injected to the EMC test board input with an injection probe. Spectrum analyzer 1 is used to monitor the output of the power amplifier, while spectrum analyzer 2 is used to monitor and verify the injected signal. The signal frequency is swept from 150kHz to 80MHz with a disturbance signal of 80% amplitude that is modulated with a 1kHz sinusoidal signal. The EUT should be placed at a specified height (10cm) above the ground plane

Diagram of Laboratory Setup for CI TestFigure 3-14 Diagram of Laboratory Setup for CI Test

Table 3-12 specifies the IEC 61000-4-6 test levels.

Table 3-12 CI Test Levels
LevelField Strength of Test Signal
V0 (10V/m)V0 (dBμV)
11120
23129.5
310140
xSpecial level that can be above, below or between the other levels. This level can be specified in product standard.

Figure 3-15 shows the actual setup for the CI test on the ADS125H18 EMC test board.

Laboratory Setup for CI TestFigure 3-15 Laboratory Setup for CI Test

Figure 3-16 shows the ADS125H18 EMC test board output data during the CI test when the ADC measures the voltage input (left) and the current input (right). The plots show that the test signals do not affect the ADS125H18 ADC when the test signal frequency sweeps from 150kHz to 80MHz. This test was also repeated coupling the interference signals into the DC port and the earth line. In all cases, the ADS125H18 EMC test board passed the CI test with criteria A.

Voltage (Left) and Current (Right) Measurements Captured during CI TestFigure 3-16 Voltage (Left) and Current (Right) Measurements Captured during CI Test

Table 3-13 shows the results of the CI test. The test result is the same for both the voltage and current channels on the EMC test board.

Table 3-13 CI Test Results using ADS125H18 EMC Test Board
TestIEC StandardTest SignalConfigurationCriterionTest Results
Field StrengthFrequency
CIIEC 61000-4-620V/m (Level >3)150kHz-80MHzVoltage InputAPass
Current InputAPass
DC PortAPass
Earth LineAPass