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ADS54J66: Powering

Moham
Intellectual 635 points
Other Parts Discussed in Thread: ADS54J66, ADS54J66EVM

Hi,

Powering ADS54J66 for the best performance(output noise and spur level) is my problem:

1- Is JESD204B supply(1.15 V) a DGND related supply or AGND related?

2- Is 1.15 V supply necessary for best performance or i can feed 1.2 V instead? Datasheet say 1.2 V is maximum recommended value but in related Eval board used for supplying JESD204B part of IC.

3- In Eval board AGND and DGND connected together? What's your propose for the best performance?

4- Is JESD204B supply pins same as digital supply pins from the point of view of supply pollution level? Can i share IOVDD supplying regulators with AVDD suppling line and have the best performance

Regards

  • 0
    TI__Guru* 91947 points

    Moham,

    The latest copy of the data sheet (December 2015) specifies IOVDD at 1.15V, not 1.2V. This cannot be shared with AVDD as these are two different voltage levels. If you meant to share DVDD and AVDD, this is not recommended either. The JESD204B pins do power up a PLL so it does have some analog circuits  where as the DVDD is true digital. The Eval board only uses one ground, which we believe provides the best performance. If you plan on using this approach, make sure to keep all analog traces away from any digital traces. I have attached a document which contains high speed board layout techniques.

    Regards,

    Jim

    0871.High Speed Serial Link Layout Recommendations.pptx

  • 0 in reply to jim s
    Intellectual 635 points
    Jim,

    Thanks a lot, so the best value for IOVDD is 1.15 V and IC is in risk with 1.2 V? separating AGND and DGND can degrade circuit performance? and if my board planes have been separated, so that's better having 3 ground planes(one for IOVDD)? or you propose having one ground plane?

    Best Regards,
    Moham
  • 0 in reply to Moham
    TI__Guru* 91947 points

    Mohan,

    Yes, use 1.15V for IOVDD. Separating AGND and DGND will degrade performance depending on board routing and layout. I would still suggest using one ground plane. It should be easier to route. If you would like, send us your layout and we will review it for you. You can also look at the layout of the ADS54J66EVM from the files under the product folder on the TI website.

    Regards,

    Jim