SPRY348A October   2023  – March 2024 RM57L843

 

  1.   1
  2.   Overview
  3.   At a glance
  4.   Defining functional safety compliance
  5.   Two attributes of functional safety system design
  6.   The recommended approach to designing functionally safe motor-control and drive systems
  7.   How TI can help you design functionally safe systems

Defining functional safety compliance

The goal of functional safety standards such as International Electrotechnical Commission (IEC) 61508 and International Organization for Standardization (ISO) 26262 is to manage and mitigate systematic faults while also being able to detect and prevent (or, at minimum, render safe) random hardware failures when they occur.

The adoption of a rigorous development process with independent verification and validation can help manage for systematic faults.

It is possible to detect, prevent or render safe random hardware failures by:

  • Having a thorough understanding of the equipment under control.
  • Analyzing the likely sources of situational hazards and their attributes, such as probability of occurrence, severity of impact and controllability of the incident.

The pairing of safety mechanisms with each situational hazard then helps designers meet quantitative metrics such as safe failure fraction (SFF) and probability of failures/hour (PFH) as required by IEC 61508. For example, a Safety Integrity Level (SIL) 2 system must have an SFF≥90% and a PFH of ≤1000 failures in time over 1 billion hours of operation.