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TVP5147M1PFP AGND and DGND Internal connection

Alberto Alcayde del Pozo
Prodigy 170 points
Other Parts Discussed in Thread: AM3715, TVP5147M1

Good morning,

Is the AGND and DGND of TVP5147M1PFP connected inside of the device?

  • 0
    TI__Mastermind 43875 points

    Indirectly these are connected but you should always connect both grounds together externally either directly or through ferrite beads depending on your layout and power supply architecture.

    BR,

    Steve

  • 0 in reply to Steve Clynes
    Prodigy 170 points

    Thank you very much for your reply. I have connected AGND and DGND balls with AGND and DGND planes of the board. Both planes are connected in the board through a jumper. 

    When we removed the jumper and I measure the impedance between AGND and DGND planes I check that I don`t have high impedance between planes. I have reviewed the design and I don´t have other connection between AGND and DGND planes. AM3715 device is used in the same board too.

    We suspect that we have a problem with ground returns in our system in which we are using 3 AM3715 and 3TVP5147M1. So we need to know if AM3715 or TVP5147M1 devices have AGND and DGND connected internally.

    Best regards,

    Alberto Alcayde

  • 0 in reply to Alberto Alcayde del Pozo
    TI__Mastermind 43875 points

    I have to be honest, pretty much every design I have seen that tries to split analog and digital grounds has had issues. More often than not splitting the grounds causes more issues than it is supposed to fix.

    In fairly low current situations you can usually avoid analog/digital interference with careful partitioning and placement such that separate planes are not needed.

    My suggestion is to use a single ground plane (or multiple, but connected to the same net with many vias) then make sure that you don't end up 'guiding' higher current return paths through regions of analog. i.e. don't have your main power supply, then analog, then heavy digital, If necessary you can use plane slots to guide current but then make sure that absolutely no signals cross the slots otherwise you will have noise and EMI issues.

    If possible I would try tying your DGND and AGND together in as many places as you can to see how that affects things.

    BR,

    Steve