How to find the default level of BOR as well as set a custom level to STM32F103CB

[Shanmugapriya]

Hi everyone,

I'm working with an STM32F103CB in my project and would like to know the default Brown‑Out Reset (BOR) threshold set for this MCU. Additionally, I’m looking for guidance on how to configure the BOR threshold to a custom level.

Any help or pointers would be greatly appreciated!

Thanks in advance.

[mfgkw]

The F103 will be reset if voltage drops below a threshold. According to DS5792 (2.3.2 Power supply supervisor) the threshold value can be influenced by 3 bits PLS[2:0] according to Table 12 "Embedded reset and power control characteristics".

See RM0008 "5.4 Power control registers"

(F103 seems not to have more sophisticated brown out behaviour like F4xx and others.)

DS5792: https://www.st.com/resource/en/datasheet/cd00191185.pdf

RM0008: https://www.st.com/content/ccc/resource/technical/document/reference_manual/59/b9/ba/7f/11/af/43/d5/CD00171190.pdf/files/CD00171190.pdf/jcr:content/translations/en.CD00171190.pdf

[Gyessine]

Hello @Shanmugapriya 
Based on table 11 of the product datasheet, ensure that the voltage does not fall below 2.0 V to ensure functionality at extreme conditions.

and like @mfgkw said, you can modify the power mode by setting the PLS bits in the power control register.

Hope that helps!
Gyessine

[Shanmugapriya]

Thank you, @Gyessine and @mfgkw, for your suggestions.

If I set PLS to 2.7 V (101), will the device using the STM32F103 IC get a hardware reset?

What will be the use of setting PLS bits?

Do we have a provision to configure the BOR in this IC?

[mfgkw]

You can use an interrupt when voltage drops. DS says: "An interrupt can be
generated when VDD/VDDA drops below the VPVD threshold and/or when VDD/VDDA is
higher than the VPVD threshold. The interrupt service routine can then generate a warning
message and/or put the MCU into a safe state"

So in case you want to make some clean up before going into reset you do it in the interrupt.

The PLS bit can be configured to have more time for cleaning up. (A capacitor in VDD would give you more time as well...)

[Shanmugapriya]

Is this interrupt similar to a power reset?
What will happen once the interrupt is triggered?

[Gyessine]

Hello @Shanmugapriya 
I think your first question is solved, and you are now asking another question.
-First question " I’m looking for guidance on how to configure the BOR threshold to a custom level."
-Second question "is this interrupt similar to a power reset?What will happen once the interrupt is triggered?"
To keep everything organized, we always try to keep every question in an independent thread to make it easier for all users to find solutions.
Can you please accept the reply that you think solved your question as the solution to make it a reference for other users, and post your new question in a new thread?
Thanks for understanding in advance!
BR
Gyessine