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DS90UB921-Q1: Schematic review

Kevin Xiong
Expert 2340 points
Part Number: DS90UB921-Q1


Hi,

Could you please help review my schematic as attachment? If I want to use coax, is there any special configuration?

Thanks.

Kevin Xiong

TI 921 COAX.pdf

  • 0
    TI__Guru** 103215 points

    Hello Kevin,

    Can you let us know what partner device is being used here?

    Thanks,

    Casey 

  • 0 in reply to Casey McCrea
    TI__Mastermind 25955 points

    Hi Kevin,

    The device on the other side of the link may impact the circuit.  Please let us know.  Thanks!

    Sincerely,
    Bryan Kahler

  • 0 in reply to Bryan Kahler
    Expert 2340 points

    Hi, Bryan,

    The other side is DS90UB940 which is designed by third party. Could you please help review my schematic with coax?

    Thanks.

    Kevin Xiong

  • 0 in reply to Kevin Xiong
    TI__Mastermind 25955 points

    Hi Kevin,

    Thank you for sharing that information.  

    With respect to the 921 the values for DOUT+ and DIN- should be 330 nF and 150 nF, respectively, as shown in the schematic.

    Are you in control of the 940?  The 940 recommended values may have changed:

    RIN+ -> AC coupling cap at 100 nF
    RIN- -> AC coupling 47 nF

    This is per a recommendation from the 940N datasheet that discusses 940+921 operation, found here: http://www.ti.com/lit/ds/symlink/ds90ub940n-q1.pdf

    VDDIO and VDD33 filter networks -> The values of the BLM18PG121SN1D differ from the EVM.  Please ensure that the supply noise is rejected as specified in section 6.4 of the DS.

    SDA and SCL -> Ensure these lines are pulled up.  Pull-ups are not seen in this schematic.  DS recommended value is 4.7kOhm.

    PDB -> Ensure the power supply sequencing meets the requirements of section 9.1 of the DS.

    Sincerely,
    Bryan Kahler

  • 0 in reply to Bryan Kahler
    TI__Mastermind 25955 points

    Hi Kevin,

    Haven't heard from you in a while - hopefully no news is good news and the issue is now resolved.  If so, to help enable others that may have the same question find the correct answer, please press the green 'this resolved my issue' button.

    If not, please let me know what other issues related to the original question remain.

    Sincerely,
    Bryan Kahler