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DAC7644: AGND and DGND conenction

Takahiro Saito
Expert 5585 points

Part Number: DAC7644

Hi team,

My customer is going to use multiple of DAC7644 on a board.

They have a question about the connection between DGND and their ground pattern. They separates the analog ground and digital ground on theri board.  In this configuration, if DGND is connected to the digital ground, they are concerned about that the noise from DG is coupled to AGND through a stray capacitance in DAC. What is a recommend connection DG to the ground pattern?

I think DGND should connect to their digital ground like following picture. Also, I think DGND and AGND should short near the IC to keep DGND and AGND same voltage level. Am I right? 

Regards,

Saito

  • 0
    TI__Guru 56523 points

    Hi Saito-san,

    Your recommendation is good, as at a minimum the grounds should be connected near the device.

    Generally, I recommend that customers layout the boards with distinct AGND and DGND regions, but ultimately the merge them to a single ground.  This is to prevent added noise caused by a stray signal that is in the wrong ground plane.

    Mr. Henry Ott has a simple explanation here: 

    Thanks,

    Paul