3.3.2 Implementation Example

The SAMA5D2 BGA289 is a full 17x17 ball grid array without any depopulated balls. In order to fit 0402 decoupling capacitors on each pin, the capacitor pads land on vias used to connect to power planes, therefore the PCB should be manufactured in respect of this constraint.

Using 0201 decoupling capacitors eliminates the via-in-pad constraint and are the preferred option due to their better performance.

Power is supplied through solid copper polygons placed on the inner layer (power layer). These polygons are formed in such a way that the signals on the bottom layer have their return path through them.

In the ATSAMA5D2C-XULT design files, the power planes are split to allow the user to measure the MPU power consumption, which was a requirement of the evaluation board. However, if this is not a requirement in your design, we highly recommend a single unsplit plane for each power rail.

In the following figure, capacitors are the green rectangles.