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DAC8718: Dual-Supply Configuration Detection

Kyle Sabourin
Prodigy 10 points
Part Number: DAC8718

Hello,
    I am trying to use the DAC8718SPAG in a dual-supply configuration (+5V AVdd, -5V AVss, +2.5V REF, +3.3V IOVdd ). I also have RSTSEL pin tied to IOVdd and USB/BTC pin tied to ground. My understanding is that the DAC should detect that it is using a bipolar supply and set an appropriate 'Offset DAC-A/B' register value of 999Ah. The DACs in my system with this configuration are starting with an offset of 0000h and a DAC data value of 8000h. This would correspond to detecting a unipolar supply with my configuration of RSTSEL and USB/BTC pins. Could I please get clarification on how this DAC detects the bipolar supply? Am I possibly not meeting some voltage threshold or is there a further configuration needed to select bipolar supply?

  • 0
    Prodigy 10 points

    I now see many people are having issues related to the power-on sequence with this device and I'm thinking that is my issue. I am performing a reset after some time with all supplies present and assumed that would clear power-on sequencing issues. Is a reset, either through configuration register D13 toggle or toggling the RST pin not a true reset in terms of configuration detection?

  • 0 in reply to Kyle Sabourin
    TI__Expert 4590 points

    Hi Kyle,

    D13 and the RST pin both perform hardware resets and should be suitable for your needs.

    Let me know if your issue persists after resetting and ensuring IOVDD and DVDD are provided before AVDD.

    Thanks,
    Lucas

  • 0 in reply to Lucas Burnette
    Prodigy 10 points

    Hi Lucas,
        This is good news regarding reset; thanks for the response. For clarification, I am resetting the device after all supplies are stable on. If I reset on a running system do I need to remove power to AVDD before reset to then apply it after IOVDDD or should reset work if all power is already applied and stable?

    Thanks,
    Kyle

  • 0 in reply to Kyle Sabourin
    TI__Expert 4590 points

    Hi Kyle,

    I would try removing AVDD from the board before the reset and then connect it afterwards.



    If this doesn't work, then try disconnecting all power from the board and follow the correct sequencing.

    Thanks,
    Lucas