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Is it acceptable to power down AVDD (+5V) while DVDD (3.3V) remains powered?

Robert Poor1
Prodigy 180 points

Part Number: ADS1248

Our system allows the +5V rail to be powered down in order to conserve power.  (The 3.3V rail is permanently powered.)  The +5V rail powers a number of devices, including the AVDD supply for the ADS1248. 

So:

  • Is it acceptable to power down AVDD while DVDD remains powered up?
  • If so, are there setup times or other considerations to take into effect after powering up AVDD (assuming DVDD remains powered)?

Thanks in advance.

  • 0
    TI__Guru 58961 points

    Hi Robert,

    Yes, it is acceptable to keep DVDD powered up while AVDD is powered down. Just make sure to heed the cautions outlined in the ADS1248 datasheet in section 11, a portion of which is restated below:

    "The power supplies can be sequenced in any order but in no case must any analog or digital inputs exceed the respective analog or digital power-supply voltage limits.Wait at least 216 tCLK cycles after all power supplies are stabilized before communicating with the device to allow the power-on reset process to complete."

    You should consider issuing a RESET command once the power supplies are stabilized to ensure the device is in a known state.

    -Bryan

  • 0 in reply to Bryan Lizon86
    Prodigy 180 points

    Bryan:

    Super helpful - we've set up the code to do exactly what you're recommending.  I just wanted to make sure it was a legitimate use case for the ADS1248.

    Many thanks -- this resolved my issue.

    - rdp

  • 0 in reply to Robert Poor1
    TI__Guru 58961 points

    Thanks Robert, glad we could help

    If you have a new question related to this ADS1248 design, please start a new thread and we will be happy to assist you.

    -Bryan