TIDUFC1 November   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
      1. 2.3.1 ADS127L21B
      2. 2.3.2 REF81
      3. 2.3.3 REF54
      4. 2.3.4 RES21A
      5. 2.3.5 THP210
      6. 2.3.6 OPA828
  9. 3System Design Theory
    1. 3.1 Range Selection
    2. 3.2 Linearity and Low-Noise Signal Chain
    3. 3.3 Calibration
    4. 3.4 Additional System Design Considerations
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Description
      1. 4.1.1 PCB Interface
      2. 4.1.2 Input Multiplexer
      3. 4.1.3 Gain Multiplexer
      4. 4.1.4 Power Supplies
      5. 4.1.5 Clock Tree
    2. 4.2 Software Requirements
    3. 4.3 Test Setup
    4. 4.4 Test Results
      1. 4.4.1 Integral Nonlinearity Measurements
      2. 4.4.2 Noise Simulation
      3. 4.4.3 Noise Measurements
      4. 4.4.4 Conclusion
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
    2. 5.2 Tools
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Author

Description

The target application for this design includes digital multimeters (DMMs) that require ultra-high precision to measure dc signals. This design achieves effective dc accuracy using the ADS127L21B, a high-performance, 24-bit analog-to-digital converter (ADC) with effective linearity. An ultra-low drift buried Zener reference, REF81, calibrates the signal chain to eliminate gain and offset errors.