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How to design a board with ICs with their own ground and power plane

nikoly

Hi to everyone,

I'm designing a 2 board layer using Eagle Cad.

This board is composed by different ICs (mainly LDO and step-up) that I have to put one next to the other in order to get the right voltage I need.

Every IC is equipped with its own demoboard and each demoboard (as you can see from attached file) has its own ground and power plane.

My doubt is how could I consider the whole board; I mean , do I have to draw each ground and power plane of each IC or can I draw one whole ground and power plane for the entire board ?

 

I have this doubt since my fear is to lose all benefits(noise rejection, thermal issues etc) in each IC I use in the board.

 

 

Hope you can give me an advice since this is the first board of this type I design

 

 

Thanks

nico

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  • Thanks Micheal for the quick reply and for all advices using 4 layers board.

    My purpose now is to have the whole board working for my home and maybe for commercial uses in the future.

     

    For this reason I should start with 2 layers board (having one Gnd plane on both side of the board) taking care mainly of the trace width (depending on the current) and of components placement.

    This because there  is no recommendation about using 4 or more layers in every IC suggested layout (on their datasheet). They only  suggest to put vias to the ground plane  without specifiing if buried, through-hole or blind (even if I think the step-up IC  need 4 layers minimum and buried vias for thermal issues).

    Do you think I could use a 2 Layer board?

     

    If yes or not (in this case i will use all you suggested for 4 layers board)  my doubt is this:

     

    starting from the LDO  there are polygons for Vin, GND and Vout signals. Same thing for the battery charger (Vbat, Vss, Vdd) and ending with the step up (Gnd polygon).

    Since I have to put them all together , do I have to draw exactly these polygon for each side of the board  or just drawing trace with the right width and length will be enough between the 3  ICs?For example the Vout of the LDO will be the Vdd of the battery charger (the input of the  second ic in the figure) so I dont know if I have to draw 2 separated  polygon (one for the VOUT  LDO and one for the VDD of the  charger), just one or simply just connecting them with one trace of the right trace and length?

     

    I dont know if the explanation of my doubt is clear! Hope so!

    Thanks again

  • in reply to nikoly

    You will probably get away with a 2 layer board, it will be better (thermally) if you get it made with 2oz copper (rather than 1oz).

    Use separate polygons on the top (component side) and as much continuous ground plane as possible on the bottom side.

     

    Join the VOUT LDO polygon with  a track to the VDD of the charger.

     

    When you've done the layout then post it here.

     

    MK

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  • in reply to nikoly

    You will probably get away with a 2 layer board, it will be better (thermally) if you get it made with 2oz copper (rather than 1oz).

    Use separate polygons on the top (component side) and as much continuous ground plane as possible on the bottom side.

     

    Join the VOUT LDO polygon with  a track to the VDD of the charger.

     

    When you've done the layout then post it here.

     

    MK

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