SFFS309A April   2022  – May 2022 TPS3704 , TPS3704-Q1

 

  1.   Trademarks
  2. 1Introduction
  3. 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
    2. 2.2 Using the FMEDA Spreadsheet Tool
      1. 2.2.1 Mission Profile Tailoring Tab
        1. 2.2.1.1 Confidence Level
        2. 2.2.1.2 Geographical Location
        3. 2.2.1.3 Life Cycle
        4. 2.2.1.4 Use Case Thermal Management Control (Theta-Ja) and Use Case Power
        5. 2.2.1.5 Safe vs Non-Safe (Safe Fail Fraction) for Each Component Type
        6. 2.2.1.6 Analog FIT Distribution Method
        7. 2.2.1.7 Operational Profile
      2. 2.2.2 Pin Level Tailoring Tab
      3. 2.2.3 Function and Diag Tailoring Tab
      4. 2.2.4 Diagnostic Coverage Tab
      5. 2.2.5 Customer Defined Diagnostics Tab
      6. 2.2.6 Totals - ISO26262 Tab
      7. 2.2.7 Details - ISO26262 Tab
      8. 2.2.8 Totals - IEC61508 Tab
      9. 2.2.9 Details - IEC61508 Tab
    3. 2.3 Example Calculation of Metrics
      1. 2.3.1 Assumptions of Use for Calculation of Safety Metrics
      2. 2.3.2 Summary of ISO 26262 Safety Metrics at Device Level
      3. 2.3.3 Summary of IEC 61508 Safety Metrics at Device Level
  4. 3Revision History

2.3.1 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): 121.5 Deg.C/W
  • Average use case power: 100mW
  • Safe vs non-safe: All permanent faults other than ROM are considered 0% safe by default. Permanent faults of ROM are considered to be 50% by default. Transient faults of digital SRAM, digital logic, and flash are considered 50% by default.
  • Operational (mission) profile used: IEC62380 Motor Control profile

  • FMEDA consider the combination of both voltage monitoring and temperature monitoring safety goals

  • Special considerations on pin level tailoring: In the out of context FMEDA
    • TPS37044-Q1 Quadruple-Channel version was used to set the pin tailoring
  • Special considerations on function and diag tailoring: In the out of context FMEDA

    • TPS37044-Q1 Quadruple-Channel version was used in the function and diag tailoring. This version is configured for up to 4 inputs and 2 RESET outputs.

  • Special considerations on the application of diagnostics: In the out of context FMEDA

    • The external System shall determine on TPS3704-Q1 reset signal whether transition to safe state is needed and execute that transition.

    • Voltage thresholds and timing requirements for TPS3704x-Q1 shall be set to match system requirements.