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Automotive Semiconductors and Functional Safety

For PMHF, the metric for the probability that a safety goal is violated due to random hardware failures, the target guideline for ASIL D is less than 10 FIT. What is this expressed as a probability per hour?

  1. A1×10⁻⁶ /h
  2. B1×10⁻⁸ /h
  3. C1×10⁻¹⁰ /h
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Answer: B. 1×10⁻⁸ /h

1 FIT is one failure per 10⁹ hours, or 1×10⁻⁹ /h. Therefore 10 FIT is 10 × 10⁻⁹ = 1×10⁻⁸ /h. PMHF (Probabilistic Metric for random Hardware Failures) is the probability per hour, averaged over the vehicle's service life, that a safety goal is violated due to random hardware failures. Target guidelines are less than 100 FIT (10⁻⁷ /h) for ASIL B and C, and less than 10 FIT for ASIL D.

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