STSPIN32G4 can't work with external 3.3V

[Sheng123]

Dear Community,

////  For new members joining the discussion, please refer to our second reply, where we’ve shared more details about the modifications and testing done on our board.
Thank you in advance for your interest and support!

I’m currently developing with the STSPIN32G4, but I’m encountering some difficulties related to flashing and powering the chip.

Below is a summary of my setup and the issues I’m facing:

 

• I'm using ST-Link V2 with the following connections:
  SWDIO, SWCLK, GND, and VCC

• I would like to use an external 3.3V power source to power the STSPIN32G4
  
  

Case 1: Powered by ST-Link V2 (VCC connected)

• STM Programmer can connect
• Flashing the image succeeds, but:
• None of the GPIOs are active
• UART has no output
• Measured VCC is only ~2.2V
  
  

Case 2: Powered by external 3.3V

• Using Arduino 3.3V output or regulated bench power supply
• STM Programmer cannot connect and shows : "Error: while trying to connect"
• ST-Link is connected with only SWDIO, SWCLK, and GND (no VCC)

Any insights or suggestions would be greatly appreciated. Thanks in advance for your support!

Best regards,

 

 

[GMA]

Hello @Sheng123,

What do you mean by "None of the GPIOs are active"? Which firmware do you use? 
If "VCC is only ~2.2V", check on your hardware where this drop is coming from? Is the board drawing too much current?

[Sheng123]

Dear @GMA 

We have change the design following the EVSPIN32G4 design but still facing the same issues 

We’re using the default 3.3V LDO solution for the STSPIN32G4 core.

However, for peripheral devices like sensors, a CAN bus transceiver, and a temperature sensor, we chose to use an external 3.3V supply.

Below is a summary of our observations:

Case 1: 12V to MV only

- STSPIN32G4 can be connected
- Firmware can be flashed
- UART output works normally

Case 2 : Provide 3.3V & 12V

- STSPIN32G4 can still be connected
- Firmware can be flashed
- (X) No UART output
- (X) All GPIOs appear inactive

 

Case 3: External 3.3V only (to test chip conduction)

Only the following Pins has voltage
PA8 - I2C2_SCL : 3.3V
PA9 - I2C2_SDA : 3.3V
PA11 - CAN_RX : 3.3V
PA12 - CAN_TX : 3.3V
PB6 - I2C1_SCL : 3.3V

PB7 - I2C1_SDA : 3.3V
This makes sense, as these are powered by the external 3.3V for peripherals.

 

However, we are unsure why the chip malfunctions or stops responding when the external 3.3V is connected alongside 12V.
Could you kindly advise whether there are any restrictions or considerations when using an external 3.3V supply in parallel with the internal LDO?

Looking forward to your insights.

Any please let me know if you need any additional information.

 

[Andrew Neil]

---

@Sheng123 wrote:

Case 1: Powered by ST-Link V2 (VCC connected)

---

A genuine ST-Link V2 by ST does not supply power, so are you using a fake/clone - like this:

https://community.st.com/t5/stm32-mcus/how-to-recognize-a-genuine-st-link-v2-versus-a-cloned-one/tac-p/703663/highlight/true#M965

[Sheng123]

Dear  @Andrew Neil 

Thanks for your response.
We also realized this and change to the official STM version, the obersvation you could look at our second reply

The issue we’re facing is that when we introduce external 3.3V into the system (to power peripheral sensors), the STSPIN32G4 stops working.

Here’s what we observed:

• We first flashed a test image that toggles the GPIO pins high/low at 1Hz.

• With only 12V input and no ST-Link connected, the G4 runs fine and toggles the GPIOs as expected.

However, once we connect the external 3.3V (to power sensors, CAN transceiver, etc.), the G4 crashes, and all GPIOs stop functioning.

We’d appreciate any insight into why this might be happening, or what kind of conflict could exist between the internal 3.3V LDO and the external 3.3V supply. We have ensured that all GNDs are properly connected, and the external 3.3V supply is clean and stable — confirmed through oscilloscope analysis, with no noticeable noise or ripple.

here is the ST-Link we are using, Since G4 don't have 3.3V output so we support external 3.3V to the device as well