ADC over range input.. ADC is broken already ?

[ammjy]

 Hello !

i have question. please, let me know..

i have stm32f051 discovery board.

before, for digital LPF, i used 5V square signal via function generator.

problem is this. stm32 Vref is 3V. 5V is already 2V over voltage.

and function generator output impedence is 50 ohm.

it's already 40mA input to ADC comporator...

i'm now not in university hostel.. so i can't test now..

i want know your opinion about my board ADC status...

please answer about my question, plase, let me know.

[suicidaleggroll]

5V with a 50R source impedance into a 3.3V part isn't too bad.  It could have killed it, but I don't think it would happen instantly, how long did you keep it connected?

However, are you sure the output is 5V?  Most 50R sources will actually put out twice they voltage they claim, under the assumption that you'll be connecting them to a 50R load and the divider will drop the voltage in half to the claimed value.  It's entirely possible the function generator was actually putting out 10V, unless you've measured it to confirm.  10V with a 50R source impedance into a 3.3V part will almost certainly blow the pin IMO.

[ammjy]

Thanks you so much, your answer Mr. suicidaleggroll !

yes. im sure and remember signal was 5V. and i did connect in 10 minuite..
(oh.. actually after read your answer. i'm not sure signal was 5V... actually i don't know well my function generator how work in his inside... my one is cheap from aliexpress..)

and i didn't saw any blow from pin. after lab works, i erased successfully flash stm32.

again, thanks a lot !