A proper layout is critical for the operation of
any switched mode power supply, especially at high
switching frequencies. Therefore, the PCB layout
of the TPSM8286xA demands careful attention to
make sure of best performance. A poor layout can
lead to issues like the following:
- Bad line and load regulation
- Instability
- Increased EMI radiation
- Noise sensitivity
Refer to the Five Steps to a Great PCB Layout for a Step-Down Converter Technical Brief for a detailed discussion of general best practices. The following are specific recommendations for the TPSM8286xA:
- Place the input capacitor as close as possible to the VIN and PGND pins of the device. This placement is the most critical component placement. Route the input capacitor directly to the VIN and PGND pins avoiding vias.
- Place the output capacitor close to the VOUT and
PGND pins and route directly avoiding vias.
- Place the FB resistors R1 and R2 close to the FB and AGND pins and place R4 close to the VSET/MODE pin to minimize noise pickup.
- The sense traces connected to the VOS pin is a signal trace. Take special care to avoid noise being induced. Keep the trace away from SW.
- To improve thermal performance, use GND vias under the exposed thermal pad. Directly connect the AGND and PGND pins to the exposed thermal pad with copper on the top PCB layer.
- Refer to Figure 8-44 and Figure 8-45 for an
example of component placement, routing, and thermal design.
- The recommended land pattern for the TPSM8286xA is shown at the end of this data sheet. For best manufacturing results, create the pads as solder mask defined (SMD) when some pins (such as VIN, VOUT, and PGND) are connected to large copper planes. Using SMD pads keeps each pad the same size and avoids solder pulling the device during reflow.