STM32F437AIH6 thermal shutdown?

[Free Claessens]

Posted on April 25, 2017 at 09:08

Hi, I am using an STM32F437AIH6 (-40 - +85dC device) in a custom design and it is failing in the thermal test (MCU completely stops). During the test I measure the MCU case temperature and MCU ambient temperature with a thermocouple.

The case temperature measures around 90dC, the ambient around 86dC right before it fails.

Peripherals in use: SDRAM, I2C accelerometer, 2x CAN + 1x ADC. So I expect not too much power dissipation in the chip (max. 0.5W I guess) so I also do not expect that the maximum junction temperature is reached.

Does the STM32F437 feature some thermal shutdown protection which I do not know of?

What could be the reason of this failure?

[waclawek.jan]

Posted on April 25, 2017 at 09:59

The 'F407 in QFP100 (VGT suffix)  I use regularly, runs roughly 30deg.C above the ambient. The UBFGA169 package has even higher thermal resistance, 52degC/W, so 0.5W may cause a roughly 25degC increase of junction temperature against ambient temperature.

Use the internal temperature sensor to get a a more precise estimate of the junction temperature.

JW

[AvaTar]

Posted on April 25, 2017 at 10:07

The case temperature measures around 90dC, the ambient around 86dC right before it fails.

Agree with Jan. The given temperature gradient suggests the MCU is your heat source.

Perhaps you could measure/provide both temperatures over time for at least 15 minutes.

[Free Claessens]

Posted on April 25, 2017 at 10:41

Ok, but is there a thermal shutdown built-in the MCU which stops the MCU when a certain temperature limit is exceeded? What is this limit?

[AvaTar]

Posted on April 25, 2017 at 11:01

If any description of this behaviour is absent in the datasheet/refmanual (I didn't check for this particular device), I can only suggest to wait for ST staff to spill the beans here.

Or nag at your ST FAE / sales representative directly ...

[Amel NASRI]

Posted on April 27, 2017 at 13:03

Hi

[e-mail]

‌,

Your application should work as expected as long as you don't the maximum junction temperature (Tj max).

You can calculate it based on the formula provided in

http://www.st.com/content/ccc/resource/technical/document/datasheet/fd/8c/0a/19/13/8f/41/99/DM00077pdf/files/DM00077pdf/jcr:content/translations/en.DM00077pdf

(Thermal characteristics section).

As already suggested by Jan, you can use the internal temperature sensor to measure the junction temperature, then implement your own shutdown of the MCU (Ex: enter standby mode when you are closer to 125°C).

You have also to review the power dissipation of your application. Referring to the table 'General Operating Conditions' in the product datasheet, the maximum power dissipation of UFBGA169 is 385 mW.

-Amel