11.1 Layout Guidelines

No PCB layout is perfect and compromises are always necessary. However, following the basic principles listed below (in order of importance) should go a long way to achieving good performance:

• Route switching currents on the top layer using short, wide traces. Do not route these signals through vias, which have relatively high parasitic inductance and resistance.
• Use a copper pour on layer 2 as a ground plane and thermal spreader, and connect the thermal pad to it using a number of thermal vias.
• Place C1 as close as possible to pin 10.
• Place C2 as close as possible to pins 2 and 3.
• Place C3 as close as possible to pin 7.
• Place L1 as close as possible to pin 1.
• Place L2 as close as possible to pin 10.
• Use the thermal pad to join AGND and PGND.
• Connect the FBS pin directly to the positive pin of C2, that is, keep this connection separate from the connection between OUTP and C2.

Figure 24 illustrates how a PCB layout following the above principles may be realized in practice.

11.2 Layout Example

Figure 24 shows the above principles implemented for the circuit of Figure 9.

Figure 24. PCB Layout Example