[PN]: STM32G431CB (B-G431B-ESC1 reference), Custom ESC with STM32 MCU
[VERSION]: MCSDK 6.3.0
[TOOL]: STM32CubeIDE 1.16.1, MotorControl Workbench 6.3.0
[DETAILS]:
I’m designing a custom ESC board based on the B-G431B-ESC1, targeting 12S (50.4V) and 20S (84V) battery systems.
The current sensing circuit from the original board was designed for a 6S battery (~25V).
From my analysis, I’ve identified the following necessary hardware changes:
Shunt resistors: Replace 0.003Ω with 0.0012Ω to handle higher currents without saturating the op-amp or ADC range.
VBUS sensing: Adjust the voltage divider from 169k/18k to 655k/18k to ensure that the sensed VBUS voltage for 84V stays within 3.3V.
Questions:
Are these changes electrically correct for reliable sensing in a 20S system?
Are there any additional component changes required (e.g., op-amp gain stages, filter caps, TVS diodes)?
What firmware-level changes will I need to perform in:
STM32 Motor Control Workbench (new shunt resistance, ADC gain, scaling factor)?
FOC current regulation loop, considering the decreased shunt voltage for same current?
ADC setup for safe and accurate sensing with higher bus voltage?
Are there recommended best practices or safety measures for designing current sensing circuits at higher voltages (20S)?
Target Behaviour:
Safe and accurate current feedback for three phases under 20S operation
Proper ADC-level VBUS sensing within 0–3.3V
Reliable current regulation performance within the MCSDK FOC loop
Steps for Reproduction:
Replace:
Shunt resistors → 0.0012Ω
VBUS divider resistors → 655kΩ / 18kΩ
Connect to STM32 ADC inputs
Update shunt values and voltage feedback scaling in MC Workbench
Test with the motor under load and validate the current accuracy
