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STM32WB55CEU6 with External Battery

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RisingElectricalEngineer
Associate

‎2024-07-10 09:52 AM - last edited on ‎2024-07-10 10:33 AM by

Hello ST Community,

 

I am working on a circuit using the STM32WB55CEU6 micro controller and bluetooth to transmit information from one of the ADC Pins. I followed some references that have the circuit powered by a USB C connection, however in my situation it will be powered by an external battery (imagining that it is 3.3V - I could add a voltage regulator later on). 

 

As I am not at all familiar with microcontrollers and this whole process in general, I was wondering if I could have someone check my circuit shown below. I have boxed out in the top left corner where the pads will be to solder in wires connecting to an external battery. I connected the battery's positive terminal (labeled the wire VBAT) to the VBAT pin, additionally, I've connected an outgoing +3.3V to the decoupling capacitors and the pocket programmer sections. So the ERC (electrical rules check) in KiCad V7 is giving me the warning “Both VBAT and +3.3V are attached to the same items”. I am wondering if this is the correct way to connect a battery. Any assistance on this would be greatly appreciated.

 

Thanks,

Rising Electrical Engineer

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Melc_dB
ST Employee

‎2024-07-11 04:19 AM

Hello @RisingElectricalEngineer,

 

First of all I can recommend you to take a look at this wiki article https://wiki.st.com/stm32mcu/wiki/Basics_of_power_supply_design_for_MCU which may help you on the design of power supply for STM32.

 

About VBAT, this is a power supply pin for the backup power domain, this is not to supply the whole application with a battery. In your case, if you only have one power supply, VBAT should be linked to VDD.

 

Then, please consider that:

  • The voltage of the battery varies depending on the charge and the current load, so a voltage regulator is recommended.
  • The battery can be damaged if over discharge, so consider add a battery management/monitoring system if not already the case.

 

In conclusion your schematic only misses a voltage regulator and a security feature for the battery.

 

Hope that answers your questions, and will helps,

Best regards,

Melchior

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

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Melc_dB
ST Employee

‎2024-07-11 04:19 AM

Hello @RisingElectricalEngineer,

 

First of all I can recommend you to take a look at this wiki article https://wiki.st.com/stm32mcu/wiki/Basics_of_power_supply_design_for_MCU which may help you on the design of power supply for STM32.

 

About VBAT, this is a power supply pin for the backup power domain, this is not to supply the whole application with a battery. In your case, if you only have one power supply, VBAT should be linked to VDD.

 

Then, please consider that:

  • The voltage of the battery varies depending on the charge and the current load, so a voltage regulator is recommended.
  • The battery can be damaged if over discharge, so consider add a battery management/monitoring system if not already the case.

 

In conclusion your schematic only misses a voltage regulator and a security feature for the battery.

 

Hope that answers your questions, and will helps,

Best regards,

Melchior

To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
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