Voltage swing from Due DAC

Hardware Arduino Due
1

Dear guys,

I have concerns about DAC of Due as below;

  1. The output voltage does not go 0 Volt even if I write 0 as output value. The DMM readings of DAC0 pin was as below;

0: 0.548V 100: 0.599V delta 51mV
1000: 1.078V 1100: 1.131V delta 53mV
2000: 1.610V 2100: 1.664V delta 54mV
3000: 2.143V 3100: 2.196V delta 53mV
3995 : 2.673V 4095: 2.727V delta 54mV

It seems that voltage swings from 0.548V to 2.727V when I wirte 0~4095. The linearity of the DAC sems OK for my application.

  1. The Voltage at 3.3V rail was 3.235V.

  2. I need voltage swing starting from 0 Volt to 10 Volt.

  3. I know I have to use OP amp to amplify the output of DAC0.

  4. The problems are;
    a) The voltage is not starting from 0 Volt. How can I make it Zero Volt using OP Amp?? I also need to amplify Max output to 10 Volt. My requirement is to make DAC0 outpout of 0.548V to Zero Volt after OP Amp and 2.727V to 10V. How??
    b) I need the DAC output stays Zero when booting and stay Zero until I write new value BUT I found the DAC0 output went to 3.235V when booting.. How can I solve this problem??

  5. I tried external 12bit DAC, MCP4728, and the voltage swing was from 0V to 3.3V which is OK but I really want to use internal DAC if at all possible.

2

I found that the output of DAC0 and DAC1 swings from 1/6 to 5/6 of the VCC which is consistant with my DMM readings.

3

You can level shift and amplify with just one op-amp. This link explains how.

4

Dear dlloyd,

Thanks for your great help. This solves level shift and amplify problem..

I still have problem of DAC output rising up to 3.3V when booting. Any idea to make it zero until I write new DAC value??

Cheers, Young

5

You could try a 10K pulldown resistor on the Due's DAC output to keep it low while it's un-configured during bootup (untested).
Another idea might be to use an analog switch ... but more information on your application and circuit would be helpful.

6

Dear dlloyd,

Thanks for your advice. I will try with a Pull down resistor. If it fails, I will use a small FET grounding non inverting input of the OP amp where DAC output is connected ( I may need a series resistor to prevent overload to DAC output when grounding) until I write a DAC value..

Thanks, Young