11.1 Layout Guidelines

As for all switching power supplies, the layout is an important step in the design. Proper function of the device demands careful attention to PCB layout. Take care in board layout to get the specified performance. If the layout is not carefully done, the regulator could show poor line and/or load regulation, stability issues as well as EMI and thermal problems. It is critical to provide a low inductance, impedance ground path. Therefore, use wide and short traces for the main current paths. The input capacitor should be placed as close as possible to the IC pins as well as the inductor and output capacitor.

Connect the AGND and PGND pins of the device to the PowerPAD™ land of the PCB and use this pad as a star point. Use a common power PGND node and a different node for the signal AGND to minimize the effects of ground noise. The FB divider network should be connected right to the output capacitor and the FB line must be routed away from noisy components and traces (for example, SW line).

Due to the small package of this converter and the overall small solution size the thermal performance of the PCB layout is important. To get a good thermal performance a four or more Layer PCB design is recommended. The PowerPAD™ of the IC must be soldered on the power pad area on the PCB to get a proper thermal connection. For good thermal performance the PowerPAD™ on the PCB needs to be connected to an inner GND plane with sufficient via connections. Refer to the documentation of the evaluation kit.

11.2 Layout Example

Figure 24. PCB Layout