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 TPSM82816 demands careful attention to ensure best
performance. A poor layout can lead to issues like bad line and load regulation,
instability, increased EMI radiation, and 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. Specific
recommendations for the device are listed below.
- The input capacitor must be placed as close as
possible to the VIN and GND pins of the device. This placement is the most
critical component placement. Route the input capacitor directly to the VIN and
GND pins avoiding vias.
- Place the output capacitor ground close to the VOUT and GND pins and route it directly avoiding vias.
- Place the FB resistors, R1 and R2, and the feedforward capacitor CFF close to the FB pin and place CSS close to the SS/TR pin to minimize noise pickup.
- Place the RCF resistor close to the COMP/FSET pin to minimize the parasitic capacitance.
- The recommended layout is implemented on the EVM
and shown in its TPSM8281xEVM-089 Evaluation Module User's
Guide and in Layout
Example.
- The recommended land pattern for the TPSM82816 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 GND)
are connected to large copper planes. Using SMD pads keeps each pad the same
size and avoids solder pulling the device during reflow.