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

2.2.3 Function and Diag Tailoring Tab

The user is expected to tailor this sheet to their specific use-case.

The 'Function and Diag tailoring' tab takes the raw (base) permanent and transient rates and distributes them among each of the design blocks (sometimes referred to hardware elements or IPs) of the device. Each row represents the lowest part of this analysis and each row gets a percentage of the FIT based on its transistor count or memory size. The user should refer to the Safety Manual in combination with this FMEDA to determine which design blocks are used in their application for a safety-related function. The design blocks that are not used can be marked as "No" for "Safety related HW element to be considered in the analysis?". This will remove these rows from the FIT calculation, which affects the safety related FIT and all derived metrics. Additionally, a set of Safety Mechanisms can be applied to each row to provide diagnostic coverage for faults associated with its function (please note that each selection here represents multiple safety mechanisms applied. For each row, the diagnostics that are applied to provide coverage for permanent faults, transient faults, and latent faults are split into separate columns so that the diagnostics can be applied to each. The list of Safety Mechanisms can be found in the 'Diagnostic Coverage' tab. TI may pre-populate the function and diagnostic tailoring selections in the function and diag tailoring tab based on one or more expected use cases for the device. Altering the selection of Safety Mechanisms will impact the Probabilistic Metrics for random Hardware Failures (PMHF) and Single Point Fault Metric (SPFM) in the 'Totals - ISO26262' tab or the Probability of Hardware Failures (PFH) and Safe Failure Fraction (SFF) in the 'Totals - IEC61508' tab.

The definition for each row in this FMEDA can be found in the Description of Hardware Component Parts chapter of the device safety manual in addition to the diagnostic options available and the full list of diagnostics available. For additional guidance on how to determine which parts are related to the system safety function, refer to 'An In-Context Look at this Safety Element out of Context' chapter of the Device Safety Manual as well.