EMI/EMC for VBAT Backup Power Supply in STM32F407G Custom Board

rohithinthingstech · ‎2024-10-24

I am designing a custom board based on the STM32F407G and need to provide backup power to the VBAT pin using an external battery. my board board must comply with EMI/EMC standards, what are the key requirements and design considerations when connecting the external battery to the VBAT pin?

Andrew Neil · ‎2024-10-28

Have you studied Application note AN4488, Getting started with STM32F4xxxx MCU hardware development:

https://www.st.com/resource/en/application_note/an4488-getting-started-with-stm32f4xxxx-mcu-hardware-development-stmicroelectronics.pdf

@rohithinthingstech wrote:
my board board must comply with EMI/EMC standards, what are the key requirements and design considerations when connecting the external battery to the VBAT pin?

It's just another digital power supply pin - so the same principles as any other digital power supply pin?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

View solution in original post

PGump.1 · ‎2024-10-24

Hi,

EMI - make sure it does not radiate.

EMC - make sure it is not susceptible to emissions...

Given that a battery doesn't have oscillator - might be safe...

"Susceptible" - might be safe there too...

I hope that helps.

Kind regards
Pedro

AI = Artificial Intelligence, NI = No Intelligence, RI = Real Intelligence.

Andrew Neil · ‎2024-10-25

"EMC" = Electro-Magnetic Compatibility = both emissions and susceptibility.

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

PGump.1 · ‎2024-10-25

@Andrew Neil they are two separate tests, conducted independently...

Kind regards
Pedro

AI = Artificial Intelligence, NI = No Intelligence, RI = Real Intelligence.

Andrew Neil · ‎2024-10-25

Yes, Emissions & Susceptibility are separate - but the combined total is EMC.

Compatibility consists of both not causing excessive Emissions, and not being excessively Susceptible to incoming interference.

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

Andrew Neil · ‎2024-10-28

Have you studied Application note AN4488, Getting started with STM32F4xxxx MCU hardware development:

https://www.st.com/resource/en/application_note/an4488-getting-started-with-stm32f4xxxx-mcu-hardware-development-stmicroelectronics.pdf

@rohithinthingstech wrote:
my board board must comply with EMI/EMC standards, what are the key requirements and design considerations when connecting the external battery to the VBAT pin?

It's just another digital power supply pin - so the same principles as any other digital power supply pin?

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.