Before beginning a design using the device, consider the following:
- A 0402-sized 0.01-µF to 0.1-µF decoupling
capacitor must be placed as close as possible to the VIN and PGND pins to
decouple high frequency noise and help reduce switch node ringing. Larger
VIN decoupling capacitors must be placed as close as possible to VIN and
PGND pins behind this capacitor to further minimize the input AC-current
loop.
- Place the power components (including input and output capacitors, the inductor, and the IC) on the solder side of the PCB. In order to shield and isolate the small signal traces from noisy power lines, insert and connect at least one inner plane to ground.
- All sensitive analog traces and components such as FB, PGOOD, TRIP, MODE, and SS/REFIN must be placed away from high-voltage switching nodes such as SW and BOOT to avoid coupling. Use internal layers as ground planes and shield the feedback trace from power traces and components.
- Place the feedback resistor near the device to minimize the FB trace distance.
- Place the OCP-setting resistor (RTRIP) and mode-setting resistor (RMODE) close to the device. Use the common AGND via to connect the resistors to the VCC PGND plane if applicable.
- Place the VCC decoupling capacitors as close as possible to the device. If multiple capacitors are used, provide PGND vias for each decoupling capacitor and ensure the return path is as small as possible.
- Keep the switch node connections from pins 2 and
11 to the inductor as short and wide as possible.
- Use separate traces to connect SW node to the bootstrap capacitor and RC snubber, if used, instead of combining them into one connection. Keep both the BOOT and snubber paths short for low inductance and the best possible performance. Also, to minimize inductance, avoid using vias for the RC snubber routing and use very wide traces. To be most effective, the RC snubber must be connected between a large SW copper shape and large PGND copper shape on the same side of the PCB as the TPS54J060.
- Avoid connecting AGND to the PCB ground plane
(PGND) in a high current path where significant IR
and L*dI/dt drops can occur.