SFFS339A December   2022  – August 2025 TLIN1431-Q1

 

  1.   1
  2.   Trademarks
  3. 1Introduction
  4. 2Hardware Component Failure Modes Effects and Diagnostics Analysis (FMEDA)
    1. 2.1 Random Fault Estimation
      1. 2.1.1 Fault Rate Estimation Theory for Packaging
      2. 2.1.2 Fault Estimation Theory for Silicon Permanent Faults
      3. 2.1.3 Fault Estimation Theory for Silicon Transient Faults
      4. 2.1.4 The Classification of Failure Categories and Calculation
  5. 3Using the FMEDA Spreadsheet Tool
    1. 3.1 Mission Profile Tailoring Tab
      1. 3.1.1 Geographical Location
      2. 3.1.2 Life Cycle
      3. 3.1.3 Use Case Thermal Management Control (Theta-Ja) and Use Case Power
      4. 3.1.4 Safe vs Non-Safe (Safe Fail Fraction) for Each Component Type
      5. 3.1.5 Analog FIT Distribution Method
      6. 3.1.6 Operational Profile
    2. 3.2 Pin Level Tailoring Tab
    3. 3.3 Function and Diag Tailoring Tab
    4. 3.4 Diagnostic Coverage Tab
    5. 3.5 Customer Defined Diagnostics Tab
    6. 3.6 Totals - ISO26262 Tab
    7. 3.7 Details - ISO26262 Tab
    8. 3.8 Example Calculation of Metrics
      1. 3.8.1 Assumptions of Use for Calculation of Safety Metrics
      2. 3.8.2 Summary of ISO 26262 Safety Metrics at Device Level
  6. 4Revision History

3.8.1 Assumptions of Use for Calculation of Safety Metrics

A number of assumptions must be made in order to calculate the safety metrics according to ISO 26262:2018 or IEC 61508:2010. The assumptions of use for the reference are detailed below:

  • Confidence level applied to permanent FIT rates: 99%.
  • Confidence level applied to transient FIT rates: 99%.
  • Neutron flux: set to 1 (equivalent to exposure at sea level, as measured in New York City)
  • Thermal management (Theta-Ja): 37.8°C/W
  • Use case power: 2.11 W
  • Safe vs non-safe: Permanent ROM faults, permanent package faults and permanent digital logic faults are considered 50% safe. Transient faults of digital logic are considered 50% safe. All other faults considered 0% safe.
  • Operational (mission) profile used: IEC62380 Passenger Compartment Profile.
  • Special considerations on pin level tailoring: Use the Pin Level Tailoring tab to adapt to the specific application.
  • Special considerations on function and diagnostic tailoring: If changes were done to the Pin Level Tailoring tab, update the Function and Diag Tailoring tab to align accordingly.