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

1.3.2.3 Experimental setup and results

The TC performance tests use a precision signal generator (DP8200) to simulate a temperature change instead of an actual K-type TC to maintain high accuracy measurements and simplify the tests. The input signal is calibrated with a Keysight Technologies 3458A digital multimeter (or similar) to eliminate error from the signal generator. Figure 1-10 shows the TC EMC test board circuit that can be used with either a VBIAS or REFOUT thermocouple biasing circuit.

VBIAS and REFOUT Biasing TC Measurement Circuits on EMC Test BoardFigure 1-10 VBIAS and REFOUT Biasing TC Measurement Circuits on EMC Test Board.

Figure 1-11 shows the measured, uncalibrated temperature error in blue and the measured, calibrated temperature error in red using VBIAS thermocouple biasing. This plot uses data collected from the 2-layer TC EMC test board operating at room temperature. The graph x−axis shows the TC temperature converted from the measured voltage applied to the ADS124S08 using the precision signal generator.

Uncalibrated VS. Calibrated Total TC Measurement Error with VBIAS BiasingFigure 1-11 Uncalibrated VS. Calibrated Total TC Measurement Error with VBIAS Biasing.

Figure 1-12 shows the measured, uncalibrated temperature error in blue and the measured, calibrated temperature error in red using REFOUT thermocouple biasing. This plot uses data collected from the 2-layer TC EMC test board operating at room temperature. The graph x−axis shows the TC temperature converted from the measured voltage applied to the ADS124S08 using the precision signal generator.

Uncalibrated VS. Calibrated Total TC Measurement Error with REFOUT BiasingFigure 1-12 Uncalibrated VS. Calibrated Total TC Measurement Error with REFOUT Biasing.