All available ground return BGA must be utilized to create the best possible electrical and thermal connection between the AM263x, AM263Px, or AM261x package and the attached PCB. Maximizing VSS BGA usage is critical from signal integrity, EMI/EMC and thermal perspectives.

Unless a separate top package heat sink is used in the design, the VSS BGA (and VDDCORE to a lesser extent) are the only heat sinking thermal connection for the BGA package. For required, thermal performance, AM26x-ZCZ PCB designs must adhere to following thermal via design requirements.

• A minimum of 49 VSS vias in the center of the BGA must be shorted to PCB ground return planes. However, if possible, and for best thermal performance, then all VSS BGA needs to be connected to PCB ground return planes.
• Solid ground return planes shall be used directly under the BGA on as many layers as possible.
• Solid ground return, or the widest possible traces shall be used on the top or bottom mounting layer for VSS BGA pad connection.
• VSS via drills shall use largest possible drill diameter. This maximizes surface area of the via, providing lowest thermal resistance.
• VSS vias need to be conductively filled, if possible.

All of these thermal via requirements must be balanced against the necessary power and signal fan-out of the design.

The AM26x devices contain both analog and digital ground return pins. Both analog and digital ground return pins need to be shorted to a common set of ground return planes on the PCB for best noise and EMI performance as this creates the lowest possible impedance path for all return currents to follow. TI does not recommend to separate these two return paths as this typically ends up with lower performance return paths for both digital and analog signal paths.