Figure 11-2 shows an example PCB layout based on the LM5145EVM-HD-20A design. The power component connections are made on the top layer with wide, copper-filled areas. A power ground plane is placed on layer 2 with 6 mil (0.15 mm) spacing to the top layer. The small area of the buck regulator hot loop is denoted by the white border in Figure 11-2. This is critical to minimize EMI as well as switch-node voltage overshoot and ringing.

The LM5145 is located on the bottom side with a surrounding analog ground plane for sensitive analog components as shown in Figure 11-3. The analog ground plane (AGND) and power ground plane (PGND) are connected at a single point directly under the IC (at the die attach pad or DAP). Refer to the LM5145EVM-HD-20A High Density Evaluation Module User's Guide and LM5146-Q1-EVM12V Evaluation Module User's Guide for more detail.

Figure 11-2 LM5145 Power Stage PCB Layout

Figure 11-3 LM5145 Controller PCB Layout (Viewed From Top)