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LMZ35003: LMZ35003 / AGND connection

S.Satoshi
Guru 21675 points
Part Number: LMZ35003

Hi,

Now I'm referring the PCB layout of LMZ35003EVM-001 that has Layer 2 as AGND plane and Layer 3 & 4 as PGND. But now our customer can prepare only inter PGND. Then which do you recommend that top AGND should connect to inter PGND with via or top AGND should not connect with via? I understand that it should be connected to improve thermal performance, but I'm concerning the impact of switching noise from PGND to AGND.

Best Regards,

Satoshi / Japan Disty

  • 0
    TI__Mastermind 28020 points

    AGND needs to be connected to PGND at one point. It is recommended to make the connect at pins 8 & 9 on the top side of the PCB. There is no need to connect them using a via.

  • 0 in reply to J Arrigo
    Guru 21675 points

    Hi Arrigo,

    Thank you for your comment. Then, do you recommend to connect top AGND plane to inner PGND with via to get better thermal performance when they can prepare only PGND as inner layer? I believe that it should not be connected, it should be connected at pins 8 & 9 as you commented at this situation also.

    Best Regards,

    Satoshi

  • 0 in reply to S.Satoshi
    TI__Mastermind 28020 points

    Do not connect AGND to PGND with vias on inner layers. Make the connect on the top-side at pins 8 & 9.

    If vias are added near pad 37 (AGND) for thermal performance, place a small isolated AGND copper area on inner layers that connects to the vias.