STM32G031K8T6使用稳压源3.3V供电，固件不能运行是怎么回事？

我想对STM32G031K8T6独立供电，以测试ADC功能。

按照UM2591的描述：使用3V3供电时，要断开SB2和SB3。我照做后，使用稳压源3.3V供电，固件不能运行。必须在断开JP1使用3V3供电VDD，同时USB要插上，固件才能跑起来。

注意到这样一段话：

6.4 Power supply
The power supply is provided either by the host PC through the USB cable, or by an external source: VIN (7 V - 12 V), +5V (5 V) or +3V3 (3.3 V) power supply pins on CN4. In case VIN, +5V or +3V3 is used to power the STM32G0 Nucleo-32 board, this power source must comply with the standard EN-60950-1: 2006+A11/2009, and must be Safety Extra Low Voltage (SELV) with limited power capability. In case the power supply is +3V3, the STLINK is not powered and cannot be used

不知是什么意思。

难道STM32G031的供电还有别于以往的MCU？需要专用电源芯片？