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ADS1292 AVdd disconnect

ccent
Intellectual 340 points
Other Parts Discussed in Thread: ADS1292

Hi,

Is it possible to remove the power supplying the analog AVdd section of the ADS1292 when the part is not being used? I would like to be able to shut down the AVdd supply to reduce power to other circuits on the rail, but I am concerned that this will cause strange behavior in the ADS1292 or on the SPI bus. The digital DVdd supply would remain powered and the part would be put into shutdown mode by the microcontroller during this period of inactivity. Please let me know if this is a viable configuration for this part.

Many thanks,

Corey

  • 0
    TI__Guru 57346 points

    Hi Corey, 

    Sorry for the delay in my reply.

    Just for clarification, are you referring to putting the device in Standby Mode (SPI command) or Power-Down Mode (via PWDN/RESET pin)?

    By turning off the AVDD supply, I believe you will have to follow the Power-On Reset timing guidelines again, as if the device was turned on for the first time. Once the supplies (AVDD and DVDD) are finally both on, this would mean waiting 32ms before the first /DRDY pulse goes low. If the supplies were to remain on, the wait time would be 10ms for both Standby and Power-Down Mode.

    I will speak with the designers and provide a more definitive answer.

    Best Regards,

     

  • 0 in reply to Ryan Andrews
    Intellectual 340 points

    Hi,

    Thanks for the reply. I am referring to a total disconnect of the power supplying the analog section (AVdd) of the ADS1292 while maintaing the digital supply (DVdd). Since I have other high power parts on the AVdd rail, I want to shut down this rail when not in use. However, I am concerned that this may damage the part or place it into some undefined state. 

    Also, I am interested in knowing if SPI communication can be achieved while only supplying DVdd and not AVdd. ie. can I place the part in power-down without supplying an analog AVdd supply?

    Thank you!

  • 0 in reply to ccent
    TI__Guru 57346 points

    Hi Corey,

    I did some tests to look into this using our ADS1292EVM and GUI software. A few things had to be modified:

    • L3 (inductor connected to AVDD supply) was uninstalled / replaced to disconnect / reconnect the supply
    • AVDD is used to power the internal oscillator, so I installed an external oscillator and the required discrete components to provide an external CLK. 

    After powering on the EVM and starting the GUI, I wrote to some registers and ensured I could read out the internal Test Signal. Then I disconnected AVDD (removed L3). At that point, I tried to change a couple registers and determine if SPI communication was still possible. At least with our software, it was not. A Register Read yielded all "0s."

    When I restored AVDD, the part powered back on with its Device Default settings. 

    So based on my observations, disconnecting AVDD only (leaving AVSS, DVDD, DGND intact) should not damage the part; however, I was not able to write to registers during this time, and previous register settings were not retained. You will likely need to issue a HW / SW reset to the device after power up (following Power-On Reset protocol) and rewrite your registers.

    I hope this is clear. Let me know if you have any questions.

    Regards,