• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 46 subscribers
  • Views 213 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DAC8311: changing behaver

Alexei Tikhonski
Prodigy 90 points
Part Number: DAC8311

I was planning to use DAC8311 in new design in pair with MSP0G3507 MCU.

Initial experiment with software simulated SPI port (toggling I/O pins) shows that part is working perfect.

Power-On Reset to Zero Scale, Straight Binary Data Format.

After connecting DAC8311 to real SPI port with TI 16 bit data format, I notice that DAC output does not behave as it supposed to.

Device become completely different part: Power-On Reset to Midscale, 2's Complement Input.

Going back to software simulated SPI port (toggling I/O pins) does not change anything.

It still Power-On Reset to Midscale, 2's Complement Input.

I am really afraid to use this part for our next design, because it can happens on production line.

Any recommendations?

Alexei

  • 0
    TI__Expert 9000 points

    Hi Alexei,

    It sounds like there may be something wrong with the MCU's communication. Could you send a screenshot of your schematic and also send an oscilloscope screenshot of the power-on sequence? If you could get the VDD, VOUT, SYNC, and DIN in the shot, that would be great, as this can tell us if the MCU is doing something weird at startup.

    Thanks,
    Erin

  • 0
    Prodigy 90 points

    Hi Erin,
    There is no power up sequence, because the device is constantly powered by battery.
    But after disconnecting it from power and connecting again, it started working normally.
    The question is: HOW did I managed to change the behavior of the DAC?
    Is there a special sequence I need to avoid making sure it will not happen again?

  • 0 in reply to Alexei Tikhonski
    TI__Expert 9000 points

    Hi Alexei,

    When you say you were seeing 2's complement input, what data were you sending to the device? What commands were you sending with the MCU during your testing?

    Thanks,
    Erin

  • 0 in reply to Erin Bowrie
    Prodigy 90 points

    Hi Erin,

    DAC was connected to 3.3V power, so full range would be from 0 to 3.3V with input code from 0x0000 to 0x3FFF

    At the beginning this was the case, next day I realize that DAC output is different:

    Code 0x0000 > DAC output =midscale

    Code 0x3FFF > DAC output =midscale

    Code 0x2000 > DAC output =0V

    Code 0x1FFF > DAC output =3.3V

    Alexei

  • 0 in reply to Alexei Tikhonski
    TI__Expert 9000 points

    Hi Alexei,

    Do you happen to have a schematic of your circuit that you can provide us? A schematic may lend some insight to this problem you found. 
    In addition, could you try replicating the issue to see if you can narrow down the cause?

    Thanks,
    Erin