5V FT pins vs. injection current on STM32G0

[Carl_G]

I am confused about the limits of the FT pins on this MCU. I think I understand the maximum voltage on an FT pin except FT_c is Vdd + 4V as long as no pulls are enabled. So with 3.3V Vdd the max voltage on most FT pins will be 8.3V is that correct? Its a bit confusing where that footnote is placed.

Beyond that, given the voltage limit is 8.3V how does it matter if the positive injection current limit is 0mA? That means I need an infinitely large resistor to prevent any injection current when the voltage is over Vdd. Or does N/A mean there is no current limit so long as the voltage is not exceeded?

Thank you.

[TDK]

> Or does N/A mean there is no current limit so long as the voltage is not exceeded?

Yes, basically this, but a few things to note here:

• Positive injection is not possible on those pins if they are below the voltage threshold. So you need to respect the voltage threshold, and the current injection is satisfied automatically.
  • 
• The "Absolute Maximum Ratings" should not be encountered during normal operation. Per the datasheet: "Exposure to maximum rating conditions for extended periods may affect device reliability."
• The max allowable voltage during normal operation is min(VDD + 3.6V, 5.5 V) for FT pins.
  • 
• (also minor note: 3.3 V + 4 V = 7.3 V, not 8.3 V)

*STM32 microcontroller GPIO hardware settings and low-power consumption - Application note