A/D input signal saturated at 3.3V, despite "5 V tolerant I/O"

[LysAn]

Dear all,

Dear all,

I use a NUCLEO_H7A3ZI_Q, connected through an external Arduino/Zio-type connector to an external signal generator, which outputs a constant voltage level.

• the input channel of the μCU appears to be saturated to 3.3V; it shows this value, even if I increase the incoming voltage to e.g. 4.0V.
• However, the manual DS13313 states, that this channel should be 5.0V tolerant (see attachment)

Could this be related to the caution notice from the UM2408 Manual (see attachment)

I wonder how the adapter board is able to saturate the value, if that is true...

Many thanks

L.A.

[Ozone]

Of course.

Read the datasheet.

[LysAn]

So I disconnected the adapter, and even now my readings don't climb above 3.3V, when I apply a higher voltage directly at pin PA3 (ADC_123_INP10) of my Nucleo board. Anyone has an explanation for that?
Cheers

[Andreas Bolsch]

Datasheet says V_AIN <= V_Ref+ <= V_DDA <=3.6V.

[Ozone · Accepted solution]

Here a snipped from a datasheet of another STM32 - I don't have nor use a H7 :

Check the respective section in the datasheet of your MCU variant.

And check for footnotes like this :

The term "5V-tolerant" does not mean "operating properly with 5V applied".
And analog pins are explicitely exempt anyway.

[mƎALLEm]

Hello @LysAn ,

Are you using the IO as digital input or analog input for ADC?

[LysAn]

Hello, @mƎALLEm I use it as an analog input for ADC. Wasn't aware about these details about voltage levels.