nRF52832 at 100 C (Rated 85C)

[Israel]

Hello,

We have a released product that is using the nrf52832 (rated at 85C). We have used this MCU and we have don't have issues so far.

Recently, it came a small opportunity that requires this same product to operate at 100C for some times, the new business is small, so spending engineering resources in a different part is not cost effective at the moment. 

That said, our management is asking us to investigate any information on the ramifications of running the chip up to 100C for 99 minute intervals multiple times per day ( maybe 4 ) ? 

Is there anything that you know that can share with us? For example, are this parts not tested therefore not rated 125C to keep cost low? or because simply they are not designed for it? Some parts are rated 125C, but we are unsure if it has different components and build quality or is it only certification. Is there a die temperature where the chip will "protect" / shutoff ? Is there a temperature "danger" where damage to the part may occur?

Also, if we where to migrate to a 125C part? which would you suggest? (assuming the path with less hardware (drop in compatible) and firmware changes necessary),

Thanks

Israel.

[Andreas]

Hi,

 

As you say the part is rated at 85 degC, meaning it is designed for and tested/validated at this temperature. That said though, the nRF52 parts that are rated at 85 degC are largely similar to the parts that are rated at 105 degC. The process is similar but there might be some design differences in some modules such that the IC operates to spec up to 105 degC, and the part is characterized and validated up to 105 degC instead of 85 degC.

Operation slightly outside the rated temperature range will likely not damage the part, but some modules might not operate to spec such that the IC as a whole might not operate as expected. Still, we need to emphasize that this is outside the maximum ratings, we do not know exactly and therefore recommend switching to use a part that is rated at 105 degC.

Unfortunately there are no drop-in compatible parts rated at 105 degC, in the nRF52-series this includes nRF52833 and nRF52820. nRF52820 has 256kB flash, 32kB RAM and comes in a QFN40 package with 18 GPIOs which might be insufficient for directly porting a typical nRF52832 application, in which case you are looking at nRF52833. nRF52833 on the other hand is a slight superset of nRF52832. You will likely have to do a bit of porting work, possibly use a different Softdevice, but it should all be fairly similar and hopefully not a too streneous task.

nRF5340 will also be rated at 105 degC, but this is still in development and SW is still in development. It is also a much more complex IC and thus at a higher price point. Also the SW will be entirely different, so I do not see this as an alternative per your descriptions.

 

Best regards,

Andreas