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Original question:

ADS54J66: Powering

ADS54J66EVM: Powering

Jerry Lipson
Prodigy 100 points
Part Number: ADS54J66EVM
Other Parts Discussed in Thread: ADS54J66, TPS82084, TPS7A8300, LMK04826

Your evaluation board schematic LMK POWER sheet 5 shows a very large network of caps and ferrite beads.

I am doing a very space constrained design and would like to know what parts of this network is absolutely necessary and what can be removed without major performance impact.

Can you quantify the impact of removing various parts of that network?

Also your  datasheet for the ADS54J66 part only has typical current draw numbers for all the supplies. I need to know the maximum current draw information to be able to design this part into my board. What are those numbers?

  • 0
    TI__Mastermind 44680 points
    Hi Jerry
    We are looking into the answers to your questions.
    Someone will respond in more detail soon.
    Best regards,
    Jim B
  • 0 in reply to Jim Brinkhurst1
    TI__Guru* 91947 points

    Jerry,

    Max analog and digital current is 10% higher than nominal.

    Regards,

    Jim

  • 0
    Prodigy 100 points

    Thank you for the answer to the second part of my question but I still urgently need an answer to the first part of my question about the possible reduction of the large power supply inductor/cap network and performance impact. It may not be possible to place all the parts shown on the evaluation board so it is critical to determine what can be removed and the possible performance impact if any.

  • 0 in reply to jim s
    Prodigy 100 points
    You resolved the second part of my issue but not the first. I still urgently need an answer to the first part of my question about the possible reduction of the large power supply inductor/cap network and performance impact. It may not be possible to place all the parts shown on the evaluation board so it is critical to determine what can be removed and the possible performance impact if any.
  • 0 in reply to Jerry Lipson
    TI__Guru* 91947 points

    Jerry,

    This EVM was designed several years ago and TI now has smaller, better performing LDO's and switchers I would suggest you use. I would replace U2, U10 and U11 with the TPS7A9101 LDO and replace U9 with a TPS82084 switcher. On the current EVM design, U15 is not used. Attached is a schematic of one of our newer EVM's that you can use as reference for these regulators. You can then request from our power group to review your schematic and offer suggestions if needed.

    Regards,

    Jim

    SCHEMATIC_dac39rf08evm_a_04262018.pdf   

  • 0 in reply to jim s
    Prodigy 100 points
    Thank you for the response. I am not using the regulators shown on the EVM (using LTM4624 switchers, LT1965 low noise LDOs & 1 TPS7A8300) as I am powering 2 ADS54J66 parts, 1 LMK04826 and other LDOs but I will look at the regulators you mentioned to see if they could possibly save some space.

    The new EVM you sent removes a few caps but still has 1 or 2 beads on each supply. Are the LMK04826 parts that susceptible to supply noise that you need so many beads?

    Are there switching frequencies that should be avoided for the switchers that feed the LDOs?

    Jerry
  • 0 in reply to Jerry Lipson
    TI__Guru* 91947 points

    Jerry,

    We normally use notch filters to filter out the switching frequency of the switchers. An example of this is a Murata NFM31PC276B0J3L.

    Regards,

    Jim

     

  • 0 in reply to jim s
    Prodigy 100 points
    Can I get the BOM associated with the dac39rf08evm schematic to look at the specifications of the actual parts used to evaluate if I can use some 0402 beads in place of the 0603 etc. to help me fit the parts on my board?
  • 0 in reply to Jerry Lipson
    TI__Guru* 91947 points

    Jerry,

    Send me your email address I can send you more info regarding the DAC.

    Regards,

    Jim