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Ground connections in a multilayer board

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  • Ground connections in a multilayer board


    I am doing my first board trying to think about signal/power integrity after watching Robert's and other videos. One month ago I wasn´t aware of this, but am designing a "complex" board and the doubts come out. I would appreciate it if you could help with them, which I think will be easy to answer for most of you.

    This is a rough blocks diagram of the PCB:
    Click image for larger version

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    Stackup used: 6 Layers
    Layer 1: Signal + Power (All the boost and buck converters components are located on the top layer)
    Layer 2: GND ( Power Ground?)
    Layer 3: Signal + Power
    Layer 4: GND + Signal
    Layer 5: GND ( "Normal" Ground?)
    Layer 6: Signal + Power

    1) My main concern is how or where to route the grounds. I have many power ground pins from boost and buck converters distributed around the PCB, as well as the common ground for all the ICs. After watching videos, it seems that splitting the ground plane (layer 2) is not a good idea, but if I use vias to connect GND signals from layer 1 to the ground plane of layer 2, I guess it will be a mess. My thought is to connect all the power ground to layer 2, and the rest of the grounds to layer 5. Is this a good way to do the layout? I am very confused. The only similar reference I could find was from ROHM:
    Click image for larger version

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    It doesn´t connect the noisy ground of a buck converter input capacitor to the common ground, but connect the ground of the output capacitor to PGND and common GND, and there isn´t PGND plane below the ground of the IC controller (AGND). In this case, is it recommending to split the Power plane of layer 2?

    I am sorry for the speech, to sum up, what is the right approach for GND layout?

    2) I am using up to 10A in the boost converter outputs, and I am trying to avoid noise at the buck converters input (they supply voltage to sensitive sensors) which are connected to the same battery connector. Please check the pictures below, what is the right way to connect the voltage power from the battery connector to the boost converters?

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    Or any other recommendation?

    3) The ground pins of the output capacitors of each boost converters are close to the other boost converter because of the limited size. I saw in other layouts manufacturers use a line or a bunch of vias to split sections like ground from Vin and Vout of boost converters. Is it a good idea to use vias between the boost converters? Please see the diagram below:

    Click image for larger version

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    I have done many simple PCBs but I am a beginner with noise, ground, etc. and this is an important task, so any help would be much appreciated.

    Thank you very much in advance
    Attached Files

  • #2
    I do not have much experience with motor controlling boards. Maybe someone else can help?