SDAA150 December   2025 ADS124S06 , ADS124S08

 

  1.   1
  2.   Abstract
  3. 1Circuit Design and Test System
    1. 1.1 Design Overview
    2. 1.2 Overview of EMC Test Board for RTD Measurements
      1. 1.2.1 Input Configurations and ADC Settings
        1. 1.2.1.1 Configuration and settings for a 3-wire RTD measurement with a low-side reference
        2. 1.2.1.2 Configuration and settings for a 3-wire RTD measurement with a high-side reference
      2. 1.2.2 Temperature Error - RTD Measurement
        1. 1.2.2.1 Calculating RTD temperature from RTD resistance
        2. 1.2.2.2 Calculating the temperature error from RTD measurements
        3. 1.2.2.3 Experimental setup and results
    3. 1.3 Overview of EMC Test Board for TC Measurements
      1. 1.3.1 Input Configurations and ADC Settings
        1. 1.3.1.1 Input Configurations
        2. 1.3.1.2 Thermocouple Characteristics and ADC Settings
      2. 1.3.2 Temperature Error - TC Measurement
        1. 1.3.2.1 Calculating temperature from TC thermoelectric voltage
        2. 1.3.2.2 Calculating the temperature error from TC measurements
        3. 1.3.2.3 Experimental setup and results
    4. 1.4 Circuit Design Considerations for EMC compliance
      1. 1.4.1 Analog Input Protection
      2. 1.4.2 Anti-aliasing Filter
      3. 1.4.3 High-voltage Capacitors on Every Input Connector Pin
      4. 1.4.4 High-voltage Capacitors and Resistors for Discharging Path
      5. 1.4.5 Series Resistors on Digital Signals
      6. 1.4.6 Digital Isolation
      7. 1.4.7 Power Supply and Protection
    5. 1.5 PCB Layout Consideration for EMC compliance
      1. 1.5.1 PCB Layer Stack-up and Ground Plane
      2. 1.5.2 Avoiding a Long Return Path
      3. 1.5.3 Avoiding 90-degree Bends in PCB Traces
      4. 1.5.4 Using Guard Ring to Isolate Interference Signals
      5. 1.5.5 Decoupling Capacitors
      6. 1.5.6 Differential Signal Routing
      7. 1.5.7 Stitching Vias
      8. 1.5.8 Layout for Isolation Barrier
      9. 1.5.9 Component Placement
    6. 1.6 Test System
  4. 2Test Details and Results
    1. 2.1 Standards and Test Criteria
    2. 2.2 Electrostatic Discharge (ESD)
    3. 2.3 Radiated Immunity (RI)
    4. 2.4 Electrical Fast Transients (EFT)
    5. 2.5 Surge Immunity (SI)
    6. 2.6 Conducted Immunity (CI)
  5. 3Schematic, PCB Layout and Bill of Materials
    1. 3.1 Schematic - RTD EMC Test Board
    2. 3.2 Schematic - TC EMC Test Board
    3. 3.3 PCB Layout - RTD EMC Test Board (4-Layer)
    4. 3.4 PCB Layout - RTD EMC Test Board (2-Layer)
    5. 3.5 PCB Layout - TC EMC Test Board (4-Layer)
    6. 3.6 PCB Layout - TC EMC Test Board (2-Layer)
    7. 3.7 Bill of Materials - RTD EMC Test Board
    8. 3.8 Bill of Materials - TC EMC Test Board
  6. 4Summary
  7. 5References

1.4.1 Analog Input Protection

Each analog input includes an external protection circuitry to protect the ADS124S08 from electrical overstress (EOS). Additionally, each analog input includes properly-selected bidirectional transient voltage suppressor (TVS) diode to help shunt transient energy away from the signal path.

The general selection guidelines are as follows:

  • TVS diode: Low leakage current, low temperature drift of leakage current, proper standoff voltage
  • Current limiting resistor: power rating, temperature drift, tolerance, ADC IDAC compliance voltage

Refer to the application note for details about protection techniques and component selection: Circuit for Protecting ADS124S08 ADC from EOS for RTD Measurement.

Analog Input ProtectionFigure 1-14 Analog Input Protection.