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RM46L852: Achieving Performance Level E

Christian Gabor
Prodigy 70 points
Part Number: RM46L852

Hello,

I noticed in the technical report for this microprocessor, they were able to achieve performance level d. I am curious why it was only able to achieve PL d. 

The functional safety of my application will need to meet performance level e. Could I achieve this by having more redundancy in the design, such as having two RM46L852 processors in my design? Or is PL e not obtainable with the TI MCUs? This seems like it would be overkill as it would have 4 total CPUs checking for inputs as well as 4 sensors. 

Thanks,

Christian Gabor

  • 0
    TI__Guru 59540 points
    Hello Christian,

    The Cat# and PL is entirely dependent on the system level implementation. ISO/EN13849 is a machinery directive so it really doesn't have any specific component level requirements. For certain, using a device like Hercules can help since we have a very high level of diagnostics. The purpose of the report you refer to is that we wanted some guidance from a third part assessor that a Cat3 PLd safety level could be achieved for a specific architectural concept (not the included HW architecture included in the report) using only 1 MCU together with an intelligent PMIC as a test channel. The novelty of this is that it differentiated from the HW implementation recommended by the ISO13849 standard at the time and opened up opportunities for design optimization for our customers.

    With that said, I can't really make any assessment on the ability to achieve PLe since this gets into some additional requirements that we haven't fully evaluated. For certain, if you follow the standard 2-channel approach it should be possible to meet the requirements of the standard but, again, it is a system level standard and therefore requires analysis specifically at the system level and in relation to your application specific safety requirements. The key is to first develop your Safety Requirements Specification, do you Fault analysis at the system level and work through the problems to see if you can meet all of the required metrics and fault tolerance needed for the desired safety level.