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What happens to STM32F407 ADC if i give it an input voltage higher than maximum VDDA that is mentioned in datasheet equals to 3.6 volts?

It will harm the micro?

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    \$\begingroup\$ Best case, the input protection diodes clamp the signal to VDDA, and the ADC output then reads out as all 1s. (so 0xFFF for a 12-bit ADC for example). Worst case, those diodes get smoked and the higher voltage makes it to the chip internals and kills the chip. Some parts can take up to 1mA thru that diode, others less. You can add some external protection, some as simple as a high value resistor in series with the signal to limit the current flow to the level the diode can handle. If indeed there is one. Check the datasheet. \$\endgroup\$
    – CrossRoads
    Jan 15 '19 at 19:53
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According to the datasheet, the STM32F407 has pins that are 5V-tolerant, which have absolute max input voltage Vdd + 4V; for the other pins abs. max is 4V. Look at Table 7 under Pinouts and Pin Descriptions to see which ones are 5V-tolerant. Note that I/O pins in analog configuration (as when configured to be used as ADC inputs) are not 5V-tolerant. Note also that these are stress ratings; don't expect it to work properly at these levels.

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  • \$\begingroup\$ As @Justme points out, pins in analog mode are not 5V tolerant. See footnote 4 to Table 7. Also in Table 7 it looks like some pins have the "TTa" I/O structure which is "3.3V tolerant" \$\endgroup\$ Jan 15 '19 at 21:12
  • \$\begingroup\$ @ElliotAlderson - Yes I should mention that explicitly, especially since the question was regarding the ADC. Fixed \$\endgroup\$
    – user28910
    Jan 16 '19 at 19:24
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No. Datasheet says the pins cannot be 5V tolerant when configured as analog IO.

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  • \$\begingroup\$ That's right. Tnx \$\endgroup\$ Jan 15 '19 at 20:22
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Yes, possibly. If the datasheet says that the maximum is 3.6V then you have to assume that any higher voltage will damage the processor.

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If you read the datasheets carefully, there seems to be an interesting progress in various STM32 device families:

  • STM32F042 - no ADC pins are ever 5V tolerant
  • STM32F407 - some ADC pins are 5V tolerant but only in digital modes
  • STM32L432 - most ADC pins are marked as 5V tolerant and there is no mention of any restrictions to that, i.e. the ADC should survive with 5V on those pins
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From F407's datasheet, this is the pin description Pin Description

This is general operating conditions which tells between -0.3V and 3.3+0.3 (If Vdda = 3.3) General Operating Conditions

Absolute maximum ratings as someone above has already said it's 4V (Only this is taken from F765 datasheet) Maximum absolute ratings

So it should be 3.6V considering Vdda is 3.3V else Vdda+0.3V

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