Practical Layout Guidelines

What are some practical layout guidelines for converters?

The following are some recommended guidelines for layout of switching converters:

i. Identify “hot loops” based on your topology and prioritize the place of those components that discontinuously switch currents

ii. SW nodes should have wide pours as necessary from IC pins to the inductor pads but not too big since they emit lots of noise due to high switching transitions; no vias should be placed in SW nodes

iii. Feedback components and traces should be far away from noise areas (SW, Vin, I2C CLK/DATA lines, etc.) and must be routed next to a solid reference plane

iv. AGND/PGND pins should be connected through a via since PGND is for the power FETs that carry high currents and generate a lot of AC noise. AGND is analog ground which must be as quiet as possible; via connection helps isolate PGND AC noise through the inductance of the via while maintaining DC potential

v. Avoid routing sensitive or switching signals across broken reference planes as this can cause noise in the signal and can couple to other sensitive signals

vi. Maximize number of thermal vias on Vin and PGND pins and place as close to the package as possible since the main source of heat dissipation must be done through the PCB’s solid copper planes

vii. When all else fails, layout guidelines for the ICs may be located at the end of the datasheet