How to deal with EMI, when required to achieve Functional Safety

How to deal with EMI, when required to achieve Functional Safety image #1

21 Jun 2023

How to deal with EMI when required to achieve Functional Safety

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When a digital system must achieve ‘Functional Safety’ (or ‘Essential Performance’ for medical applications) we need to use EM RESILIENCE to deal with the risks that can be caused by EMI.


The reason for needing EM RESILIENCE is that:

1. Programmable digital systems (hardware and software) have far too many possible digital states to ever be thoroughly tested.  Even once.

2. Programmable digital systems are non-linear, so we can’t interpolate. 
This means we can’t test a percentage of digital states and assume that the results suggest anything about the behaviour of the untested states.
E.g. Even if 99% of the digital states tested as being safe-enough, we must not assume that the untested 1% would also be safe-enough. But we can’t normally even get close to testing 1%!

This inherent and unavoidable unpredictability of programmable digital systems is why they cannot ever be shown to be safe enough by any affordable test programme. So, EMC immunity testing cannot be sufficient on its own, for safety – it needs to be used as part of an EM RESILIENCE approach.  
If you need more background than this, please read:


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