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O
OTM98
Graduate
December 8, 2023
Solved

STM32U575ZIT6 microcontroller - issue when configuring PLL1 as the clock source

  • December 8, 2023
  • 1 reply
  • 5680 views

Hello forum members,

I am currently working on a custom PCB based on the STM32U575ZIT6 microcontroller. I've encountered an issue when configuring PLL1 as the clock source – the code generates a hard fault. However, when selecting HSI or HSE as the source, everything works fine. The challenge is that I am unable to achieve the desired 160MHz clock speed without using the PLL.

I've observed that in the RCC (Reset and Clock Control) section, when I choose HSE or HSI, the regulator_voltage_scale is set to level 4. Interestingly, manually changing it to levels 3, 2, or 1 results in a hard fault.

I would appreciate any insights or suggestions regarding this issue. Has anyone encountered a similar problem with PLL1 configuration on the STM32U575ZIT6, or does anyone have recommendations on resolving hard faults related to clock configuration?

Thank you in advance for your assistance.

Best regards,

    This topic has been closed for replies.
    Best answer by TDK

    I see a single 10 uF capacitor in your design. This is a bulk capacitor, not a decoupling capacitor, and serves a similar but different purpose. Please refer to the hardware design guide.

    TDK_0-1702057960152.png

    The lack of decoupling capacitors can result in the hard fault you are seeing at higher clock speeds.

    1 reply

    T
    TDK
    Super User
    December 8, 2023

    > custom PCB based on the STM32U575ZIT6

    Sounds like a power issue. Do you have a nucleo board or other known good hardware you can test your code on?

    Perhaps share a schematic, or check for the usual things:

    • VDD/VDDA all powered and decoupled.
    • VCAP all decoupled and showing valid voltage.
    • VSS/VSSA all connected to GND.
    • Sufficient VDD bulk capacitance.
      O
      OTM98Author
      Graduate
      December 8, 2023

      Hello,

      Thank you for your input. I've checked the power supply using STM32CubeProgrammer, and the voltage reads at 3.28V. Additionally, I've tested the code on a Nucleo-U575ZI-Q board where everything functions as expected. However, on my custom PCB, I'm encountering difficulties manipulating PLL1.

      Despite these measures, the issue persists on my custom PCB. I appreciate any further suggestions or insights into potential areas I should investigate.

      Thank you for your assistance.

      Best regards,

       

       

      check.jpeg

      T
      TDK
      Super User
      December 8, 2023

      Do you have any decoupling caps? Typically a 0.1 uF at each VDD pin.

       

      Hardware design guide:

      https://www.st.com/resource/en/application_note/an5373-getting-started-with-stm32u5-mcu-hardware-development-stmicroelectronics.pdf

       

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