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Andrew Neil
Andrew Neil
Super User
September 5, 2024
Solved

STM32F030 PC13,14,15 current sink limits?

  • September 5, 2024
  • 4 replies
  • 4636 views

AndrewNeil_0-1725556635883.png

 

Is it OK to use these pins as current sinks for driving LEDs ?

 

AndrewNeil_1-1725557015423.png

 

    Best answer by STTwo-32

    Hello @Andrew Neil @Tesla DeLorean @AScha.3 

    Sorry for my late replay, I just received this answer from the concerned person:

    " The switch is only impacting GPIO source capabilities. No limitations if IO is set in output low level."

    Best Regards.

    STTwo-32

    4 replies

    STTwo-32
    STTwo-32
    ST Technical Moderator
    September 5, 2024

    Hello @Andrew Neil 

    As it is mentionned on the 3rd line of the note on the screenshot:

    "These GPIOs must not be used as current sources (e.g. to drive an LED)." For Curent sink, i will check this and get back to you ASAP.

    Best Regards.

    STTwo-32 

    To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
    Tesla DeLorean
    Tesla DeLorean
    Guru
    September 5, 2024

    Good question, the P/N gates probably the same size, but the ground ring is probably more robust, and not gated like VDD/VBAT path

    I'd tend toward it being Ok, but will watch for the official response.

    Slack pins for LEDs, the PA13/PA14 often can be used and still facilitate debug connectivity if the code is aware.

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    Andrew Neil
    Andrew NeilAuthor
    Super User
    September 5, 2024

    plus the reason stated for the limitation is that these pins are fed  "through the power switch", and that's what limits their sourcing capabilities.

    I presume this is "the power switch":

    AndrewNeil_0-1725559013974.png

     

    On that basis, if it's the whole story, sinking should be OK ... ?

     

    "the switch only sinks (sic?) a limited amount of current" sounds like a typo, though?

     

    A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
    Tesla DeLorean
    Tesla DeLorean
    Guru
    September 5, 2024

    >>plus the reason stated for the limitation is that these pins are fed "through the power switch", and that's what limits their sourcing capabilities.

    What's gating it, or how robust the wiring/metalization is feeding it across the die.

    That was definitely my "hot-take" on the documentations wording, and that the return-path on the common VSS side was significantly more substantial, and not switched/gated.

    The geometry of the IOCELL's transistor might also be smaller/slower, I vaguely recall a +/- 3mA specification in some STM32 family docs.

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    STTwo-32
    STTwo-32Best answer
    ST Technical Moderator
    September 17, 2024

    Hello @Andrew Neil @Tesla DeLorean @AScha.3 

    Sorry for my late replay, I just received this answer from the concerned person:

    " The switch is only impacting GPIO source capabilities. No limitations if IO is set in output low level."

    Best Regards.

    STTwo-32

    To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.
      Andrew Neil
      Andrew NeilAuthor
      Super User
      September 17, 2024

      Thanks - it would be helpful if that could be clarified in the datasheet.

      A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
        waclawek.jan
        waclawek.jan
        Super User
        September 17, 2024

        @Tesla DeLorean,

        Nice pun! :)

        @Andrew Neil,

        Great question too!

        @STTwo-32,

        > Thanks - it would be helpful if that could be clarified in the datasheet.

        +1  (and I'd spell it "datasheets").

        JW

         

          Andrew Neil
          Andrew NeilAuthor
          Super User
          February 12, 2025
          @waclawek.jan wrote:

          (and I'd spell it "datasheets").

          Indeed - another one here:

          https://community.st.com/t5/stm32-mcus-products/pc13-gpio-usage-recommendation-on-stm32g491mct/td-p/771811

          @STTwo-32 

          A complex system that works is invariably found to have evolved from a simple system that worked.A complex system designed from scratch never works and cannot be patched up to make it work.
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