Automotive Semiconductors and Functional Safety
What is the main functional safety purpose of running logic BIST and memory BIST in an automotive microcontroller at power-up or before driving?
- ATo find latent faults that do not show up in normal operation, such as those in the safety mechanisms themselves, and raise the latent fault metric (LFM)
- BTo skip pre-shipment testing at the factory and eliminate test costs
- CTo automatically raise the CPU operating frequency and speed up processing while driving
Show answer and explanation
Answer: A. To find latent faults that do not show up in normal operation, such as those in the safety mechanisms themselves, and raise the latent fault metric (LFM)
Even if safety mechanisms such as the ECC correction circuit or comparators are broken, this does not show up in normal operation, so such faults remain latent. Testing the chip's own circuits with logic BIST and memory BIST at power-up finds such faults before driving and raises the LFM. Running BIST takes time, during which normal processing cannot be done, so the design must also consider startup time constraints. It is not a replacement for shipment testing or a means of speeding up processing.
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