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DAC9881: Impedance b/w AGND and DGND

Ryuuichi machida
Guru 12610 points
Part Number: DAC9881

Tool/software:

Hello,

Customer asked following information.

* Impedance b/w AGND and DGND

Is it possible to disclose above information ?

Best Regards,

  • 0
    TI__Mastermind 41403 points

    Hi Machida-san, 

    I am checking to see if we have any information on this. Typically, we recommend shorting AGND and DGND close to the device with a low impedance trace. 

    Best,

    Katlynne Jones

  • 0 in reply to Katlynne Jones
    Guru 12610 points

    Hello Jones-san,

    Thank you for your reply.
    >I am checking to see if we have any information on this. 
    Thank you for your confirmation. Here is our background of this question.

    * Customer found there is/are DAC9881 on custom board which have different impedance from other their custom board between AGND and DGND.
    So, if you can disclose the spec, we would like to confirm this difference is within the spec and whether we have no problem.

    Could you please also give your comment whether we can see difference of impedance b/w AGND and DGND depending on device individually or lot of device ?

    Best Regards,

  • +1 in reply to Ryuuichi machida
    TI__Mastermind 41403 points

    Hi Machida-san,

    I checked with the design team on this and there are back-to-back diodes (high impedance, I do not have an exact number) connected between the two grounds. This means they should be kept within 300mV of each other to avoid causing one of the diodes to conduct. The device is meant to have the same ground reference for both AGND and DGND. 

    Best,

    Katlynne Jones