Inquiry, powering EVSPIN32G4 with 6V & current sensing

[Sheng123]

Dear Community,

We are considering using the STSPIN32G4 to integrate and control the motor in our system. The primary reason for selecting it is that our battery supplies 6V-8.4V, which falls within the STSPIN32G4's 5.5V-75V range.

We have a few questions regarding the EVSPIN32G4:

1. Input Voltage Limitation
   We are interested in purchasing the EVSPIN32G4 to test it out. However, we noticed that the product specifications state the input voltage range as 10V-75V, while the components appear to support down to 5.5V. We would like to understand the reasoning behind this limitation. 
   The best case is we can directly using our battery supplies 6V-8.4V, to power the board.  
   
   

2. Op-Amp Configuration and PA2
   As per our understanding, PA2 is used as OPO1 and should output the voltage difference to be sent to an ADC pin for current sensing and processing. However, PA2 does not seem to be connected to any other GPIO, leading us to wonder how this Op-Amp is functioning.

   • Can the STSPIN32G4 directly read the voltage from PA2 without connecting it to an ADC input?
     
     According to 
     

     we should set the Pins PA2, PA6, PB1 to ADC instead of OPAMP3_VOUT?

     
   • We referred to the steval_spin3201_schematic (EVB for STSPIN32F0) and noticed that OP3O is connected to PA5 (ADC) for current measurement. Could you clarify how this is handled in EVSPIN32G4?
     

3. Role of the STM32F103CBT6 on the EVSPIN32G4
   The STSPIN32G4 is a powerful MCU, and we are considering running our three-closed-loop PID control directly on it. However, we noticed that the EVSPIN32G4 also includes an additional STM32F103CBT6 MCU.

   • What is the purpose of having this extra MCU on the board?
   • Would there be any concerns or limitations if we were to run the full PID control on the STSPIN32G4 itself?
     
     
4. Meanwhile, we are also planning to design our own motor controller using STSPIN32G4. 
   We would like to ask how to set the VCC? 
   

   According to the user manual, VCC should at least higher than 5.5V, so can we use VM to Power VCC? Our VM is battery 6-8.4V which can be fluctuating due to motor behavior. Or should be use DC-DC providing stable 6V for VCC? 
   We would like to know your suggestion

Looking forward to your insights!
Best regards.

[Cristiana SCARAMEL · Accepted solution]

Hello @Sheng123 and welcome to the ST Community.

Here are the answers to your questions:

1. The default configuration of the EVSPIN32G4 is for using the embedded buck regulator so an adequate margin is needed on VM to have a regulated VCC output voltage of at least 8 V. In your case it is possible to directly connect VM to SW and VCC bypassing the buck regulator.
2. On same PA2 pin it is possible to connect at same time the Operational Amplifier output and proper ADC input. You can use the STM32CubeMX to quickly explore possible configurations.
   The interconnection between operational amplifier and ADC for STSPIN32F0 is different to STSPIN32G4. The latter is an high-end device having internal routing for these analog blocks.
   
3. The STM32F103 microcontroller implements the ST-Link V2 debugger and programmer for the STSPIN32G4. The STSPIN32G4 is able to manage a full software stack for driving two BLDC motors simultaneously and more. Have a look at MCSDK library (X-CUBE-MCSDK).
4. As suggested in "point 1" you can short together VM, SW, VCC and REGIN. The STSPIN32G4 is able to drive power MOSFETs if VCC remains above 5.5 V including any bounce on the supply rail.
   However having a VCC falling down to 6 V could affect the switching performance and losses of the power stage so proper MOSFETs should be selected.

[Sheng123]

Hi @Cristiana SCARAMEL 

Hi @Cristiana SCARAMEL,

Thanks for your response!
I would like to double-check the SW connection based on our configuration:

1. Battery Power Connection -> VM, VCC, and REGIN , providing 6~8.4V.
2. External 3.3V Connection -> VDD, VDDA, VBAT, and VREF+ Providing 3.3V.

Given this setup, do we still need to connect SW as shown in the reference design?

Additionally, since we are bypassing the bulk regulator:

• Can we leave SW floating?
• Or is it still recommended to connect SW to VM? Since in this case, SW would act as a power input instead of an output, we are unsure if this is acceptable for the chip.

Looking forward to your clarification. Thanks!

[Cristiana SCARAMEL]

Hello @Sheng123 

In your case SW pin need to be connected to VM, do not leave it floating.
So provide your battery voltage to VM, SW and VCC. Refer to Figure 7 of STSPIN32G4 datasheet.

If you want to use the internal 3.3 V LDO regulator of STSPIN32G4 the REGIN pin must be connected to battery voltage as well.

If you need to use an external 3.3 V regulator you have to provide this voltage to both REGIN and REG3V3 pins. Refer to figure 12 of STSPIN32G4 datasheet.