11.1 Layout Guidelines

For best overall performance, place all the circuit components on the same side of the circuit board and as near as practical to the respective pin connections. Place ground return connections to the input and output capacitor, and to the regulator ground pin as close to each other as possible, connected by a wide, component-side, copper surface. The use of vias and long traces to create circuit connections is strongly discouraged and negatively affects system performance. This grounding and layout scheme minimizes inductive parasitic, and thereby reduces load-current transients, minimizes noise, and increases circuit stability. A ground reference plane is also recommended and is either embedded in the PCB itself or located on the bottom side of the PCB opposite the components. This reference plane serves to assure accuracy of the output voltage, shield noise, and behaves similar to a thermal plane to spread heat from the device. In most applications, this ground plane is necessary to meet thermal requirements.

11.2 Layout Example

Figure 22. LM3420 Layout