3.3.2 Implementation Example

The SAMA7G54 BGA343 MPU is a depopulated 21x21 ball grid array. The selective ball depopulation allows the MPU to be routed on a four-layer PCB, using only two layers for signal routing. The depopulation also facilitates decoupling capacitors placement near the power inputs. Use 0201 sized decoupling capacitors and 0402 sized bulk capacitors.

In Figure 3-7, capacitors are the green rectangles.

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