STM32 working with impulsive magnetic field condition. Something to take care?

[MBrig.1]

Hi all, I have an application under test with MCU STM32F411 that working in impulsive high magnetic field generate by a big inductor. Below the specification:

• duration of impulse 400us;
• intensitiy of magnetic field is 2,5 Tesla peak;
• magnetic filed has a shape of sine wave with 400us duration that is 1 cycles.
• repetition of impulse is in range of 1Hz to 150Hz repetition (1s to 6ms).
• pcb with MCU and EEPROM are apply over coils at 1cm distance

I would like to know if these conditions are dangerous for STM32F411 its internal flash source code application or SRAM data that may be currupt by magnetic field.

Any suggestion to keep control internal MCU or SRAM content that can be currupt by impulsive high magneti field?

[MHAJJ · Accepted solution]

Hello MBrig,

ST does not provide a specific magnetic immunity rating for the STM32 microcontrollers, and the overall behavior of the application will rather depend on the quality of the PCB. still, I can say from my experience the F4 family does have a good immunity to the magnetic field.

-From your description of the magnetic field, it seem to me that the intensity is rather high, 2.5 Tesla correspond to 1994250 A/m which is a big number.

-The range of the frequency is close to power grid frequency (50Hz ~ 60Hz) There is a standard for that "IEC 61000-4-8: Testing and measurement techniques – Power frequency magnetic field immunity test" for more specific use cases there is "IEC 61000-4-39: Testing and measurement techniques – Radiated fields in close proximity – Immunity test".

-Is your clock system is stable ? are you using HSE ? I would expect the clock system to be first impacted, also if you are using ADC that can be sensitive too.

-For the internal data you can implement some software safety tests, like a periodic test check on constant data or have two copies of a variable in different locations and compare when used.

Regards,

Mahmoud.

[MBrig.1]

Thank you for your answer.

I report here the test that show that EEPROM and FLASH exposed to this impulsive magneti field. Both contenents is save and check in continuos tests loops.

One solution is to execute application program only after impulse is expired to avoid interference with ADC.

This product is used in magnetic therapy, and the impulse currents are in the order of 1\2KAmper

It seem the HSE is not affected by this impulses.

COnclusion: until now it seem STM32F4 and EEPROM tolerate this magnetic intensity..... more update with more long tests

Thank for share your suggestions.

Regards

Maurizio Brignoli