Nucleo F303 outputs only 2.1V on DAC

[JulienD]

Posted on January 02, 2018 at 19:17

Hi,

Using this nucleo board, the DAC outputs only voltage from 0 to 2.1V while VDD is 3.3v.

Where's the trick?

Thanks

Julien

#dac #nucleo-f303

[Tesla DeLorean · Accepted solution]

Posted on January 02, 2018 at 19:27

What voltage do you see when you don't connect anything to the pin?

The DAC has no current sourcing ability, perhaps you need to buffer via an op-amp?

[JulienD]

Posted on January 02, 2018 at 19:42

Hi Clive,

Thanks for your answer.

Hum... When I connect nothing to the pin, the voltage is 0 - 3.3v.

I dived in the sheet, max current is 100 µA.

With my configuration it is 150µA...

[T J]

Posted on January 02, 2018 at 21:50

when you adjust the R1 to say 33k, did you get the 3.3V you wanted ?  

that works out at 97uA

I am interested to see this result.

[JulienD]

Posted on January 03, 2018 at 14:15

I tried 75k+1k on the previous schematic : 3v....

I also tried 68k directly on the eval board with nothing else around, : 2.8v...

Julien

[T J]

Posted on January 04, 2018 at 09:11

sounds like you need a 100k or a little higher, the drive must be less than 100uA