TIDUFG5 December   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Insulation Monitoring
    2. 1.2 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 TIDA-010985 Overview
      2. 2.2.2 Solving for the Unknown Isolation Resistances
      3. 2.2.3 Addressing Large Time Constant Cases
      4. 2.2.4 Prediction Algorithms
      5. 2.2.5 Understanding Error Sources
    3. 2.3 Highlighted Products
      1. 2.3.1 LP-MSPM0G3507
      2. 2.3.2 TPSI2240-Q1
      3. 2.3.3 RES60A-Q1
      4. 2.3.4 TLV9002-Q1
      5. 2.3.5 TPSM33620-Q1
      6. 2.3.6 TPS7A2033
      7. 2.3.7 ISOW1044
      8. 2.3.8 TSM24CA
      9. 2.3.9 TLV431B
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Software
    3. 3.3 Test Setup
      1. 3.3.1 Hardware Test Setup
      2. 3.3.2 Software Test Setup
    4. 3.4 Test Results
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
      3. 4.1.3 PCB Layout Recommendations
        1. 4.1.3.1 Layout Prints
    2. 4.2 Tools and Software [Required Topic]
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Authors

1.1 Insulation Monitoring

There are a number of methods for measuring insulation. However, the two most common methods are AC current injection and resistive bridge. In general, the AC current injection method is flexible for various operation conditions and is widely used in DC charging but has higher complexity and cost compared to the resistive bridge method. Regardless of the method, the approach has to meet the standard requirements such as accuracy, response time, and operating voltage limits. One of the key challenges associated with the resistive bridge method is dealing with a large RC time constant. Some systems such as megawatt chargers require very large Y-capacitances (for example, 4µF). This reference design, TIDA-010985, implements the resistive-bridge approach, and is specially designed to deal with large Y-capacitances by employing a novel predictive algorithm to shorten the measurement time without requiring heavy computation such as floating-point operations. In addition, this new design topology limits the voltage variation on the Y caps. Table 1-2 shows a comparison overview of the various methods.

Table 1-2 Comparison of Various IMD Methods
METHOD ADVANTAGES DISADVANTAGES

AC current injection

  • Typically sold as a standalone module
  • Can measure energized and non-energized lines
  • No reduction in insulation resistance during measurement
  • Supports UL 2231-2 including large Y caps
  • High hardware complexity and cost
  • High software complexity (AC signal processing, floating point math)

Resistive Bridge

  • TIDA-01513, BQ79731 EVM
  • TIDA-010232 (MCU on isolated GND)
  • Easy implementation – both hardware and software
  • Low cost
  • Low calculation effort
  • Does not support UL 2231-2 for large Y caps (> 100nF)
  • Does not support IEC 61851-23 due to high voltage swings relative to PE during measurement. Limits applications to < 500 Vbus
  • Only capable of measuring energized lines
  • Slightly reduces insulation resistance during measurement

Balanced Resistive Bridge + Prediction Algorithm

  • TIDA-010985 (MCU on Earth GND)
  • Easy implementation – both hardware and software
  • Low cost and computationally light
  • Limited voltage swings relative to PE during measurement, supporting IEC 61851-23
  • Supports UL 2231-2 including large Y caps
  • Only capable of measuring energized lines
  • Slightly reduces insulation resistance during measurement