This is the first time I am designing a product for an automotive application; could I get some help in the following general area?
According to AECQ100, there are two temperature grades for automotive: Grade 0 (-40 to 150 degC) and Grade 1 (-40 to 125 degC). How do I know when to target the design for one or the other temperature grade? Is the grade dependent on the target application or some other factors (operating margins, etc).
The target application is a product to be used in recreational vehicles (RVs, boats, etc)
AEC-Q100 has following
Grade 0 (or A):
-40°C to +150°C ambient operating temperature range
Grade 1 (or
Q): -40°C to +125°C ambient operating temperature range
(or T): -40°C to +105°C ambient operating temperature
Grade 3 (or I): -40°C to +85°C ambient operating
Grade 4 (or C): -40°C to +70°C ambient
operating temperature range
Commercial would align with Grade
3 and Industrial would align with Grade 2 and like you said Grade 0 and 1 align with automotive. More specifically with the automotive grades Grade 0 is usually used under the hood (due to harsher ambient conditions) whereas Grade 1 is used elsewhere in the vehicle. What specificly is your target application? Where in the RV / boat will the electronics be housed?
Please let me know if you need anything else,
Thanks for your quick response.
The target application is a device mounted next to the battery system that provides power to the appliances of the RV. This is not the same battery that is used to start the engine. The RVs I have seen include the service battery somewhere else other than under the hood; then I should target the design for grade 1.
From what you have told me Grade 1 is what I would recommend with your application. Please let me know if you need anything else.
Thanks for the quick turn around.
No easy answer! You'll need to predict the thermal environment at the point where the chip is soldered on to the PCB.
Generally, I've started with the physical location of the module, whether it is in the engine compartment, in the passenger cabin, etc and the vehicle manufacturer's specs for ambient temperature and air flow at that location. Next is the physical construction of the module and heat sinking to the PCB. All aluminum chassis? Plastic/metal clamshell? Any thermal bonding between the PCB and chassis? PCB dimensions/part locations, copper fill percentage? Then need the worst case power dissipation for the chip in question, and worst case dissipation of other devices on the PCB. A thermal analyst can then make a reasonable model to predict peak temperatures in order to make the 0 vs. 1 decision.
As a rough guide, usually Grade 0 applications are under-hood, where ambient temperature specs can easily be 105 to 125C. Grade 1 usually in-cabin, or a chassis location not directly exposed to heat from the engine, exhaust or turbo charger.
Similar to Oscar I'm looking for parts that are automotive grade 1. How can I tell which TI parts meet this grade? Will they have a Q as part of the part number?
Different automotive qualified parts will have different grades which you will not be able to tell form just Q1 at the end of the part number. You will have to look on the product page or the datasheet for the ambient temperature (TA) spec that will tell you the "grade" that the part is qualified for. This information in usually found on the second page in the ordering information table.
Also if you look at the full orderable part number, the letter that is in between the part number and the package designator is the grade. Here are two examples:
The grade temperatures again are defined as:
Grade 0 (or A): -40°C to +150°C ambient operating temperature range
Grade 1 (or Q): -40°C to +125°C ambient operating temperature range
Grade 2 (or T): -40°C to +105°C ambient operating temperature range
Grade 3 (or I): -40°C to +85°C ambient operating temperature range
Grade 4 (or C): -40°C to +70°C ambient operating temperature range
Hope this helps. Please let me know if you need anything else,
When can Grade 4 be used; Could it possibly be used for behind the dash electronics? Do these temperature grades apply to both new manufacured vehicles and aftermarket applications for used vehicles? Your prompt reply is greatly appreciated.
Grade 4 devices and their application are usually identified by the OEM. As our devices range from Grade 1-Grade 3, there is little information on the application of Grade 4 devices.
I'd also like to clarify that current AEC Q100 standard show Grade 4 qual to be from Ta = 0C to 70C, not -40C to 70C as mentioned earlier in the thread.
We would encourage all customers to use Grade 3 and above device as these device are also guaranteed to work in the temp range of 0C to 70C. There is also the concern that 0C is not that cold and many places around the world usually will drop below 0C in the winter. Therefore, Grade 3 and above devices have the additional advantage of being qualified down to -40C.
Thanks and Best Regards,
Thank you for your prompt reply. This is very helpful information. Does this mean that any component that TI provides is at least Grade 3? Your assistance is greatly appreciated.
Yes, that is correct. Any TI component will be at least Grade 3.
Once again, thank you for the prompt reply. That is great information on the minimum grade of TI components.
I'd like to clarify that TI automotive devices are usually Grade 3 and above. TI sells a lot of devices at varying temperatures, and TI devices in general are not all Grade 3 qualified - just the automotive parts.
Thanks and Best Regards,
Thank you for the clarification. You have been extremely helpful.
I am just a bit confused that for DDR2/DDR3 memory devices in automotive grade the maufacturers only specify the case-temperature instead of ambient temp.
They show max 105°C tC, but I assume they would not stand 105°C tA, because the tC is typically several degrees hotter than the ambient temperature.
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