• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 46 subscribers
  • Views 303 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.

Original question:

DAC81404EVM: how to estimate settling time

DAC81404: Indication of Stable Power Output Other Than Waiting for Settling Time

he dajiang
Prodigy 196 points
Part Number: DAC81404


I am using 81404 as voltage source. My application requires fast speed: meaning once voltage output is stable, my MCU must control other device.

Is there any hardware indication like a pin changing for low to high to indicate that? Otherwise I have to wait for max settling time.

  • 0
    TI__Guru 54603 points

    Hi He,

    Unfortunately, we do not have a "settling complete" indicator or function.  Settling time is dominated by slew rate and external factors like capacitive load.  Could you consider a voltage supervisor for this case?

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 196 points

    Hi Paul,

    Thanks for your reply. I am afraid it may cause more delay because my DAC output has a few hundred values or steps, not just only one. For each output value, after MCU configures DAC, then MCU needs to configure voltage supervisor (VS), for which how much time it takes to complete, and how accurate it can be. I just saw a intro video: which shows the VS can generate a signal once voltage is above a threshold. However for a DAC output, reaching a certain value does not mean it has stabilized (settled), does it?

  • 0 in reply to he dajiang
    TI__Guru 54603 points

    Hi He,

    A DAC usually has two settling components: large-scale settling and small-scale settling.  Large-scale settling is dominated by the slew rate of the device and will usually complete once the output is at around 95% the final values.  After that, small-scale settling becomes the dominate component.  Small-scale settling is usually depended on the cap load on the output and may feature ringing as it overshoots and settles to the final value.  You might consider using a voltage supervisor to notify you when the output is at this 95% mark, then add a few microseconds of small-scale settling time.  Note that larger steps require longer settling time.

    Thanks,

    Paul