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LMZ31710 AGND / PGND CONNECTION

Unknown Unknown8
Prodigy 110 points
Other Parts Discussed in Thread: LMZ31707, LMZ31710, LMZ31704

Hello,

i have a question about the GND's of the LMZ31710 or LMZ31707 modules.
On the PCB we have only one GND Plane. Where is the best point on the PCB top connect AGND and PGND? Or should we go directly to the GND Plane with the AGND?

Thanks


  • 0
    TI__Mastermind 28020 points

    The LMZ31710, LMZ31707, and LMZ31704 have their AGND and PGND connection internal to the device. There is no need to connect them externally.

    See the Layout Considerations section of the datasheet (page 26) for information and a typical recommended layout.

  • 0 in reply to J Arrigo
    Prodigy 30 points

    Just so I understand this, you're saying that AGND and PGND are internally connected.  And there's a note on p.26 of the datasheet that's more emphatic, "Keep AGND and PGND separate from one another".  So if we're not supposed to tie the two grounds together outside of the device, am I correct to assume that I should tie PGND to my board's ground ... and, from my board's point-of-view, leave AGND floating (i.e. not tied to my board's ground)?  

  • 0 in reply to G. Bechman
    TI__Mastermind 28020 points

    Yes, tie PGND to your board's GND. Keep AGND separate from PGND.