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RRIDDICC
RRIDDICC
Associate III
May 23, 2025 7:48 PM UTC
Solved

what if PA2=5V in analog mode?

I can c in RM0033 (Rev9) Figure 18, that PA2 is connected with low impedance to a diode to V_DD, if PA2 is configured as analog input...

In Doc ID 15818 Rev 9 I see that R_ADC is at least 1.5kR...

If I connect PA2 in analog mode directly to 5V: Would I create a high current through that diode to V_DD (in my case 3.3V)? Or would the current be less than 1mA (1.4V/1500)? Google's Gemini and DeepSeek say, that that would damage the ADC or its MUX...

In RM0033 (Rev9) Figure 13 it looks like, I can still read the analog value on PA2, if PA2 is configured as digital output (open drain and BSRR|=(1<<2)).

Should I connect PA2 via 50kR to the difficult voltage? I cannot use a voltage divider, because that would interfere with the external pull-up resistor at PA2... I try to read CC1 of a USB-C host port... and DeepSeek says, that the USB-C device might possibly decide to connect CC1 to 5V, although I hoped, that the USB-C cable would not allow that...

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STOne-32
STOne-32Best answer
ST Technical Moderator
May 24, 2025 6:26 PM UTC

Dear @RRIDDICC ,

as Explained above if the pin GPIO is configured in Analog Mode , maximum VIN is VDDA/VREF+ + 0.3V . Exceeding that value , a physical damage may happen on Our Analog Circuitry and so whole MCU . Have a look here :

https://www.st.com/resource/en/application_note/an4899-stm32-microcontroller-gpio-hardware-settings-and-lowpower-consumption-stmicroelectronics.pdf

Have a good day,

STOne-32

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4 replies

TDK
TDK
May 23, 2025 11:05 PM UTC

Why not use it as a digital input instead? Dont see analog mode being necessary here.

Datasheet will have limits allowed in analog mode.

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    RRIDDICC
    RRIDDICCAuthor
    Associate III
    May 24, 2025 7:59 PM UTC

    CC1 and CC2 can have different voltage levels in the beginning... e. g. appr. 1.7V, which would not allow me to detect, if a device showed up, because VIL is less than 1V at VDD=3.3V...

    AScha.3
    AScha.3
    Super User
    May 23, 2025 11:17 PM UTC

    >what if PA2=5V in analog mode?

    cpu is dead.

    If you feel a post has answered your question, please click on " Best Answer ".
      STOne-32
      STOne-32Best answer
      ST Technical Moderator
      May 24, 2025 6:26 PM UTC

      Dear @RRIDDICC ,

      as Explained above if the pin GPIO is configured in Analog Mode , maximum VIN is VDDA/VREF+ + 0.3V . Exceeding that value , a physical damage may happen on Our Analog Circuitry and so whole MCU . Have a look here :

      https://www.st.com/resource/en/application_note/an4899-stm32-microcontroller-gpio-hardware-settings-and-lowpower-consumption-stmicroelectronics.pdf

      Have a good day,

      STOne-32

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