Are ATmega48/168/328 suitable for automotive applications?

Question

I'm trying to figure out if it's ok to use ATmega48 in a homemade project involving some safety-related aspects with moving vehicles. (the project will be a control board for excavator joysticks)

There's this post from 2006 - Atmel introduces 8-bit AVR flash MCUs for automotive applications But I can't understand if it means all ATmegas are automotive-grade or some of them are. And how do I tell one from another? Do they have to have some special index?

Adding to the confusion, there's this datasheet from Microchip/Atmel - ATmega48/88/168 Automotive which literally has "Automotive" in the name and on the bottom of every single page but then it says in the disclaimer that "Atmel products are not suitable for, and shall not be used in, automotive applications." That's kind of like making a diving gear that shall not be used for diving.

Answer 1

The CPU is the least of your difficulties if you're making a safety-related project with moving vehicles. Honestly, tread into this area with great caution.

The caveat at the botttom of the datasheet is standard across Atmel (and extremely similar across all manufacturers), and actually reads "Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications." (My emphasis). Your lawyer will tell you whether being sold as "automotive grade" counts as "specifically provided".

Automotive parts have different part numbers, see the ordering information of automotive data sheet:

I couldn't find any ATMega48-15AT for sale, but you can see 328PB parts very clearly marked Automotive (at Atmel's sales web site):

You might be interested in the answers to Is "automotive" grade always better? which describes some of the ways "automotive grade" differ from the ordinary ones. In brief, it depends on the part.

My understanding for the ATMega CPUs is that amongst other things they are essentially the same but have a slightly reduced nominal specification (clock rates etc) in order to qualify adequately on reliability across the temperature range. ("If you use it more gently we will make a stronger promise about reliability.") They may or may not have more QA during manufacturer; they are likely to have better batch traceability etc.

The "automotive grade" merely means the manufacturer has done a certain amount of testing and promising against automotive industry standards. I believe it's common to use non-marked parts and do the testing yourself. And of course there is an awful lot of system-level testing and proving.

Having said all that, use the simplest possible parts, as conservatively as possible, with as much safety mechanism as you can. In comments you say you want a "MCU that will be guaranteed to not have random reboots or hardware glitches". No one will give you that guarantee. In any case, these problems have almost entirely board-level, not CPU-level causes. Make sure you have good reliable power, take very good care over the clock generation, use the brown-out detector, watchdog etc. Make sure every input and output is failsafe etc. Audit any libraries as carefully as your own code: if your application is simple enough, consider avoiding libraries altogether.

Answer 2

There are some major differences between an excavator and automotive. Automotive is for highway use, such as cars, buses, motorcycles etc.

For the described usage, the main concern is regarding machine safety. If you are working withing Europe/EU, look into standards like ISO 13849. Not sure if applicable in other parts of the world though. But if not, there are likely other similar standards.

Those standards will tell you what you need to do to fulfill any safety requirements applicable. Likely, it is in one way or another achievable using one or more ATMega microcontrollers. There are usually many ways of achieving an acceptable level of safety, including both pure instructional (saying "You shall not be close to the machine when it's running"), technological (redundancy, emergency stop etc.) and concerning the development process.

Answer 3

The question doesn't seem to mention compliance with any safety standard, but suggest you look for devices with support for Functional Safety. Where if a device manufacturer targets Functional Safety they normally say which safety standard(s) support is for.

E.g. the Microchip website has Functional Safety for 8-bit Microcontrollers(MCUs)

If you want more processing power than an 8-bit Microcontroller, Functional safety on the Texas Instruments website allows you to select either:

• Arm-based microcontrollers
• Arm-based processors
• C2000 real-time microcontrollers

Support for Functional Safety can extend to other devices than microcontrollers/processors to such as Power Management or Motor Drivers, which might be relevant to a control board for excavator joysticks.

Disclaimer: I have no direct experience of designing products certified to a particular safety standard.