Unable to read stepsize of DAC

[akash07]

I have configured DAC in nucleol496zg board using an internal voltage reference of scale around 2.048V , it is 12 bit DAC so step size would be around 0.5mv but when i write

  HAL_DAC_Start(&hdac1,DAC_CHANNEL_1);
  HAL_DAC_SetValue(&hdac1, DAC_CHANNEL_1,DAC_ALIGN_12B_R,0);

In multimeter it shows around 24.7mv-25mv for all the count values up to 25mv instead of step size DAC. Only if I give greater DAC count value (which produce above 25mv) it gives the correct millivolts in multimeter.

[waclawek.jan · Accepted solution]

You probably have the buffer on, in which case the output is not rail-to-rail. See VDAC_OUT parameter in the DAC characteristics table in datasheet.

Also mind the rather limited output current capability of the DAC, especially when buffer is off.

JW