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bernhardb
Visitor II
January 23, 2025
Solved

STM32L562 max pin voltage / pins driven in unpowered state / current injection on pins

  • January 23, 2025
  • 3 replies
  • 1249 views

Hello ST,

1. ds12736 Rev.4 states in Table 24 that the abs. max. voltage on any pin is at least +4.0V (but this may be further limited by an injection current limitation)

2. ds12736 Rev.4 states in Note 4 on p.145: "Positive injection (when VIN > VDDIOx) is not possible on these I/Os and does not occur for input voltages lower than the specified maximum value."

3. ds12736 Rev.4 states in Table 25 that I_inj(pin) is specified as -5/+0 mA on all pins.

4. AN4899 Rev.3 says on p.13: "Positive-injection current is the current induced when VIN > VDD." and "0 mA means that current injection can damage the GPIO and induce STM32 malfunction."

 

These statements taken together seem to be contradictory.

So the question: May STM32L562 GPIO pins be driven in a range from 0 V to 3.3V when VDD and/or VDDIO is unpowered or below 3.3V? The datasheet seems to imply "Yes", but AN4899 seems to indicate the opposite in the context of the specified I_inj(pin).

    This topic has been closed for replies.
    Best answer by Sarra.S

    Hello @bernhardb, 

    The absolute maximum voltage rating of +4.0V indicates the maximum voltage that can be applied to the pin without causing permanent damage. However, this does not imply that the pin will function correctly at this voltage, especially if VDD or VDDIO is unpowered or below 3.3V.

    The AN and the table indicate that positive injection current is not allowed (0 mA). This means that if VIN>VDDIOx, no positive current should be injected into the pin, as it can cause damage or malfunction.

    So the answer is no, the STM32L562 GPIO pins should not be driven in the range from 0V to 3.3V when VDD and/or  is unpowered or below 3.3V.

     

    3 replies

    S
    Sarra.SAnswer
    ST Employee
    January 23, 2025

    Hello @bernhardb, 

    The absolute maximum voltage rating of +4.0V indicates the maximum voltage that can be applied to the pin without causing permanent damage. However, this does not imply that the pin will function correctly at this voltage, especially if VDD or VDDIO is unpowered or below 3.3V.

    The AN and the table indicate that positive injection current is not allowed (0 mA). This means that if VIN>VDDIOx, no positive current should be injected into the pin, as it can cause damage or malfunction.

    So the answer is no, the STM32L562 GPIO pins should not be driven in the range from 0V to 3.3V when VDD and/or  is unpowered or below 3.3V.

     

      B
      bernhardbAuthor
      Visitor II
      January 24, 2025

      Hello Sarra,

       

      Thank you. Can I enquire what is then meant by Note 4 that for the pins of this part positive injection "does not occur for input voltages lower than the specified maximum value"?

      S
      Sarra.S
      ST Employee
      January 24, 2025

      Hello @bernhardb, 

      That means that the positive injection occurs when the input voltage exceeds the supply voltage V​DDIOx.

      The "specified maximum value" refers to the maximum input voltage that can be applied to the I/O pins without causing positive injection. 

      Is that somehow clearer? 

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