LM5145 datasheet(48/60 Pages) TI2

48 / 60 page

• Make the ground connections to the LM25139 controller as shown in Figure 7-23. Create a power

ground directly connected to all high-power components and an analog ground plane for sensitive analog

components. The analog ground plane for AGND and power ground plane for PGND must be connected at a

single point directly under the IC – at the die attach pad (DAP).

• Connect the MOSFETs (switch node) directly to the inductor terminal with short copper connections (without

vias) as this net has high dv/dt and contributes to radiated EMI. The single-layer routing of the switch-node

connection means that switch-node vias with high dv/dt do not appear on the bottom side of the PCB. This

avoids e-field coupling to the reference ground plane during the EMI test. VIN and PGND plane copper

pours shield the polygon connecting the MOSFETs to the inductor terminal, further reducing the radiated EMI

signature.

• Place the EMI filter components on the bottom side of the PCB so that the components are shielded from the

power stage components on the top side.

Figure 7-24. Layer 2 Full Ground Plane Directly Under the Power Components

Cin1-4

VIN

GND

0.3mm

vias

Tightly-coupled return path

minimizes power loop impedance

0.15mm

Vias

See also Improve High-Current DC/DC Regulator EMI Performance for Free With Optimized Power Stage Layout application brief

Figure 7-25. PCB Stack-Up Diagram With Low L1L2 Intra-layer Spacing

LM25139

SLVSJ80 – OCTOBER 2025

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LM5145 Datasheet(PDF) 48 Page - Texas Instruments