TIDA035 October   2020


  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Two-point Insulation Resistance Measurements
  5. 3Equation Verification by Simulation
  6. 4Op-amp Caused Error Analysis
    1. 4.1 Input offset voltage
    2. 4.2 Input bias current
    3. 4.3 Open-loop gain
  7. 5Summary
  8. 6References


The existing reference design TIDA-01513 is based on single-point isolation leakage error measurement. However, more and more customers require two-point isolation leakage error detection. Two-point isolation leakage error means leakage errors from both positive terminal and negative terminal of high-voltage battery to chassis ground happen at the same time. It is more common to express the required insulation resistance rather than the leakage current, according to International Standards such as ISO6469-1. The insulation resistance provides the information of the possible amount of leakage current.This document explains how to implement two-point insulation resistance measurements based on the existing TIDA-01513 circuit, and discusses the impact of non-ideal characteristics on measurement accuracy.