A proper layout is critical for the operation of a switched mode power supply, even more so at high switching frequencies. Therefore, the PCB layout of the TPS6281xM device demands careful attention to ensure operation and to get the specificed performance. A poor layout can lead to issues like poor regulation (both line and load), stability, and accuracy weaknesses increased like EMI radiation and noise sensitivity.
See Section 12.2 for the recommended layout of the TPS6281xM device, which is designed for common external ground connections. The input capacitor must be placed as close as possible between the VIN and GND pin.
Provide low inductive and resistive paths for loops with high di/dt. Therefore, paths conducting the switched load current must be as short and wide as possible. Provide low capacitive paths (with respect to all other nodes) for wires with high dv/dt. Therefore, the input and output capacitance must be placed as close as possible to the IC pins and parallel wiring over long distances as well as narrow traces must be avoided. Loops that conduct an alternating current must outline an area as small as possible, as this area is proportional to the energy radiated.
Sensitive nodes like FB need to be connected with short wires and not nearby high dv/dt signals (for example SW). Since they carry information about the output voltage, they must be connected as close as possible to the actual output voltage (at the output capacitor). The capacitor on the SS/TR pin as well as the FB resistors, R1 and R2, must be kept close to the IC and connect directly to those pins and the system ground plane.
The package uses the pins for power dissipation. Thermal vias on the VIN and GND pins help spread the heat into the PCB.
The recommended layout is implemented on the EVM and shown in the TPS62810EVM-015 Evaluation Module User's Guide.