Clarification of Max OD Pin Voltage

[Rogers.Gary]

Hello:

In the STM32L452 data sheet, page 94 is table 20 of voltage characteristics. On the line with Vin, for "Input voltage on FT_*** pins", it says the MAX INPUT voltage is min (Vdd,Vdda,VddUSB) + 4.0

I interpret this as: The minimum voltage in the application, plus 4V. BUT not to exceed 5.5V. Is this correct?

Now, and OD pin is configured/driven as a "output", but in reality it's really an "input" with the drain connected to a node. In my case, it's connected to a resistor that is pulled up to a voltage that could be as high as 5.3V.

Is this within range of acceptable voltage? I think it is, I just want to disambiguate the input and output difference.

NOTE: Please ignore the post "open drain maximum voltage", it somehow got posted with no content.

[Peter BENSCH · Accepted solution]

Well, that is roughly what is meant. Expressed quite correctly:

• MAX INPUT voltage is min (Vdd,Vdda,VddUSB) + 4.0V

means something like

• MAX INPUT voltage is the smallest value of (Vdd,Vdda,VddUSB), plus 4.0V

As far as the pin with open drain is concerned, it is indeed an output "from the STM32's point of view", because it can be used to control a subsequent input stage directly (usually with pull-up) or a bus line via wired-or. And yes, this open-drain pin can switch at a maximum of 5.5V as long as the internal pull resistors are deactivated.

Does it answer your question?

Regards

/Peter

[Rogers.Gary]

Yes, and clarifies the data sheet. That voltage makes it handy since so many power devices have a range of 5.5V.

Thanks !

[S.Ma]

It is important for the power up and down transition.

[Peter BENSCH]

Great!

If the problem is solved, please mark this thread as answered by selecting Select as best, as also explained here. This will help other users find that answer faster.

Regards

/Peter

[Rogers.Gary]

Thanks again 👍