Does STM32F103 VDDA have to be powered on?

 Yes, the VDDA pin on the STM32F103 microcontroller must be powered for the proper operation of the device. VDDA is the supply voltage for the analog circuitry, such as the ADC (Analog-to-Digital Converter), DAC (if available), reset circuitry, and the internal voltage reference.



Here’s what you need to know about powering VDDA:

1. Why VDDA Needs Power

  • Analog Functions: VDDA supplies the power for the ADC, DAC, and analog peripherals. Without it, these components won't function.
  • Reset Circuit: VDDA is essential for the correct operation of the internal reset circuitry.
  • Voltage Reference: It powers the internal reference voltage, which is crucial for ADC accuracy.

2. When VDDA Must Be Powered

  • If you are using analog peripherals like ADC or DAC, VDDA is mandatory.
  • Even if you are not using analog features, VDDA should still be connected to the same voltage as VDD to ensure the proper operation of internal circuitry and avoid potential malfunctions.

3. VDDA Voltage Range

  • VDDA must typically be connected to the same voltage as VDD (the digital supply), as stated in the STM32F103 datasheet. For instance:
    • If VDD is 3.3V, VDDA should also be 3.3V.
  • Ensure VDDA is properly decoupled with capacitors (e.g., 100 nF and 1 µF) as close to the pin as possible to ensure stable operation.

4. Consequences of Not Powering VDDA

  • Analog Features Disabled: Without VDDA, the ADC and any other analog peripherals won't work.
  • Unstable Operation: Even if analog features aren't used, not powering VDDA can lead to instability or unpredictable behavior.
  • Reset Issues: The internal reset circuit may not function properly, affecting the microcontroller's startup or operation.

5. Powering Recommendations

  • Connect VDDA to the same power supply as VDD.
  • Use proper decoupling capacitors for VDDA to minimize noise and stabilize the analog circuitry.
  • Follow the guidelines in the STM32F103 datasheet and reference manual for proper PCB layout and power design.

In conclusion, while it may be technically possible to leave VDDA unpowered in some minimal configurations where no analog features are used, doing so is not recommended, as it can lead to unpredictable behavior and potentially violate the specifications of the microcontroller. Always power VDDA to ensure reliable operation.

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