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ADS7924: questions

adomino
Intellectual 1000 points

Part Number: ADS7924
Other Parts Discussed in Thread: TPS24751

Hello,

I have a couple of questions on the ADS7924

  1. can I combine AGND/DGND or do I need to keep them separate? if separate, they will be tied together locally with a 0-ohm
  2. looks like AVDD needs to be greater than or equal to  DVDD – could I just use the same voltage for both(2.5V, 3.3V or 5V all meet both requirements)? or is there a benefit for separate? is it best to keep the AVDD closer to the Analog input voltage to get more resolution?
  3. I only plan to use 3 channels, can I leave unused floating?
  4. ABS max on the analog input voltage shows a max of 0.3V… is this correct, or should it be in relation to AVDD?? hopefully, since my input is from the TPS24751 it will be a full scale voltage of 675mV

Thanks!

  • 0
    TI__Expert 5585 points

    Adomino

    Please see below answers to your questions

    1. It is better to have seperate ground plane for aGND and DGND. You need to connect these ground planes together with smal,l thick copper trace on your board (Or 0 ohm as mentioned by you)

    2. Yes you can use same supply for AVDD and DVDD. Make sure you locally decouple AVDD and DVDD pin with decoupling capacitor (1uF should be good enough)

    3. If you are not using any channel then it is better to pull it down through resistor to GND.

    4. ABS max rating on input pins is with respect to AVDD. It should be AVDD+0.3V (0.3V is typical forward drop of internal ESD diode)

    Please let me know if you need any additional information

    Thanks & Regards

    Abhijeet