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 TPS629203 demands careful attention to make sure proper operation and to get the performance specified. A poor layout can lead to issues like the following:

• Poor regulation (both line and load)
• Stability and accuracy weaknesses
• Increased EMI radiation
• Noise sensitivity

See Figure 11-1 for the recommended layout of the TPS629203, which is designed for common external ground connections. The input capacitor should be placed as close as possible between the VIN and GND pin of the TPS629203.

Provide low inductive and resistive paths for loops with high di/dt. Therefore, paths conducting the switched load current should 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 should be placed as close as possible to the IC pins and parallel wiring over long distances as well as narrow traces should be avoided. Loops that conduct an alternating current should outline an area as small as possible, as this area is proportional to the energy radiated.

Sensitive nodes like FB and VOS need to be connected with short wires and not nearby high dv/dt signals (for example, SW). As they carry information about the output voltage, they should be connected as close as possible to the actual output voltage (at the output capacitor). The FB resistors, R1 and R2, should be kept close to the IC and connect directly to those pins and the system ground plane. The same applies for the S-CONFIG/MODE and VSET programming resistors.

The package uses the pins for power dissipation. Thermal vias on the VIN, GND, and SW pins help to spread the heat through the PCB.

In case any of the digital inputs (EN or S-CONF/MODE pins) need to be tied to the input supply voltage at VIN, the connection must be made directly at the input capacitor as indicated in the schematics.

The recommended layout is implemented on the EVM and shown in the TPS629203EVM User's Guide.