3.3.2 Implementation Example

The SAMA7D65 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 3-6, the 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.