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RisingElectricalEngineer
RisingElectricalEngineer
Explorer
July 10, 2024
Solved

STM32WB55CEU6 with External Battery

  • July 10, 2024
  • 1 reply
  • 1515 views

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

Best answer by Melc_dB

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

1 reply

M
Melc_dBBest answer
ST Employee
July 11, 2024

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

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