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UCC28019A: Layout considerations

Tomer Bruchiel
Intellectual 620 points
Part Number: UCC28019A

Hi,

I am designing a board using the UCC28019A,

I saw an example of the layout on the EVM and some points on the datasheet.

The EVM uses a 2 layers PCB while my PCB is 6 layered.

The stack up of the layers is usually:

L1 - components + traces + ground plane

L2 - GND

L3 - traces (signals)

L4 - Power

L5 - GND

L6 - components + traces + ground plane

In that configuration I always have an adjustment ground plane next to either a power or a signal plane to produce a return path.

I can follow the example of the EVM, putting most of the components on the top layer and the SMD parts and trace on the bottom layers.

My questions are:

1. Should I mirror the bottom layer to all other layers or at least to the ground layers?

2. Should I only mirror the ground planes to the ground layers?

3. Leave the power plane under the PFC section blank?

4. Can I use the signal layer for traces such as JP2 - which in the EVM is a wire jumper?

Any other considerations I should take into account?

Thanks,

Tomer

  • 0
    TI__Genius 10555 points

    Hi Tomer,

    If by mirror you mean to align components with the planes through the board then yes, that would be a best practice to reduce trace length.  It's all about the shortest, most direct power paths.

    Regarding the ground planes, L2, L5, I think it would be best to make them as large as possible as they will act as shields for EMI; only leave keep-out areas for your vias to pass through (with >20 mils clearance to keep signal noise out of the ground plane).

    I'm not sure what you mean by leaving the power plane under the PFC section blank. If you mean opening the ground on L2 under the PFC power stage, then no, I would keep ground plane under there for the reason stated above.

    You can use the signal layer for JP2.  That was likely used because the designer did not have the luxury of multiple signal layers.

    Regards,

    Ray

  • 0 in reply to Ray DiCecco
    Intellectual 620 points

    Hi Ray,

    Thank you.

    Sorry for not being clear about the mirroring.

    In the EVM, all the traces, including the ground and power planes are edited on the bottom layer.
    By mirroring I mean should I edit the exact same planes as the ones on the bottom on all other layers?
    I guess not from your explanation above - correct me if I am wrong.
    So the best practice, I should fill up the ground layers and keep the separation between the Power GND and Signal GND?

    Thanks,
    Tomer

  • +1 in reply to Tomer Bruchiel
    TI__Genius 10555 points

    Hi Tomer,

    There is no need to mirror the planes on the other layers.

    Yes, fill the ground planes as much as possible and separate signal ground and power ground.

    Regards,

    Ray