• Locked Locked
  • Replies 3 replies
  • Subscribers 47 subscribers
  • Views 457 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

DAC 1280 problem

Hua Ai
Prodigy 150 points

Other Parts Discussed in Thread: DAC1280, OPA211

Hi there,

We are debugging a weird problem related to DAC 1280 and wondering if anyone has seen a similar problem.

Basically, we are using a FPGA to generate a digital bit stream for the DAC 1280 to generate a sine wave. The sine wave looks good most of the time, but sometimes on power up, the sine wave is clipped (one side of the peaks are flattened out) due to a DC offset, but the amplitude and frequency are unchanged. If we toggles the nPWDN signal to shut down the DAC and turn the DAC back on again, at most of the time the sine wave would be corrected again.

Later on we found that "powering up" is not an essential step to reproduce this. We could have the DAC powered up in a "good" condition so the sine wave is good, then just toggles the nPWDN signal to make the sine wave go bad. Of course, when it's bad, we can toggle the nPWDN again and it may be good again. 

When we were toggling the nPWDN signal, the same digital bit stream are still driving the DAC. The nSYNC were tightened to high and Gain select pins were set to "000".

Could it be that we need to SYNC the bit stream after the nPWDN was toggled to high again? or could it be that we should change the bit stream to a sequence of "10101010" when the nPWDN signal is toggled to '0'? Or it's just a bug in the DAC device?

Appreciated!

Hua

  • TI__Prodigy 305 points

    I'm a system engineer that supports the DAC1280 device.

    I have not encountered the problem with the DAC1280 as decribed. The problem is likely not the DAC1280 but could be related to the external opamp /V converter not coming out of power down state properly. Please check that your circuit drives the op-amp shutdown inputs to the specified level for operation. The application section of the DAC1280 shows a push-pull comparator driving the shutdown pin of the OPA211 opamp. This circuit has been verified.

    -Regards,

    Mark

  • in reply to Mark Berarducci
    Prodigy 150 points

    Hi Mark,

    Thank you for your reply. We are checking our shutdown circuits and will update you without our findings.

    Regards,

    Hua

  • in reply to Hua Ai
    Prodigy 150 points

    Hi Mark,

    We ties op-amp power down controls to low so the op-amps are always on, then toggle the nPWDN pin of the DAC1280, the problem still reproduces.

    Does that tell us the problem is not related to the op-amps?

    Regards,

    Hua