10.1 Layout Guidelines

When laying out the printed circuit board, the following guideline should be used to ensure proper operation of the IC. These items are also illustrated graphically in the layout diagram of Figure 36

• Recommend a four-layer PCB for good thermal performance and with maximum ground plane. 3" x 3", four-layer PCB with 2-oz. copper used as example.
• Place the decoupling capacitors right across VIN as close as possible.
• Place output inductors and capacitors with IC at the same layer, SW routing should be as short as possible to minimize EMI, and should be a wide plane to carry big current, enough vias should be added to the PGND connection of output capacitor and also as close to the output pin as possible.
• Place BST resistor and capacitor with IC at the same layer, close to BST and SW plane, >15 mil width trace is recommended to reduce line parasitic inductance.
• FB could be wide and must be routed away from the switching node, BST node or other high efficiency signal.
• VIN trace must be wide to reduce the trace impedance and provide enough current capability.
• Place multiple vias near GND and near input capacitors to reduce parasitic inductance and improve thermal performance.