IRU3138CS datasheet(12/18 Pages) IRF

12 / 18 page

Rev. 1.0

01/29/04

IRU3138

www.irf.com

Layout Consideration

The layout is very important when designing high fre-

quency switching converters. Layout will affect noise

pickup and can cause a good design to perform with

less than expected results.

Start to place the power components. Make all the con-

nections in the top layer with wide, copper filled areas.

The inductor, output capacitor and the MOSFET should

be close to each other as possible. This helps to reduce

the EMI radiated by the power traces due to the high

switching currents through them. Place input capacitor

directly to the drain of the high-side MOSFET. To reduce

the ESR, replace the single input capacitor with two par-

allel units. The feedback part of the system should be

kept away from the inductor and other noise sources

and be placed close to the IC. In multilayer PCB, use

one layer as power ground plane and have a separate

control circuit ground (analog ground), to which all sig-

nals are referenced. The goal is to localize the high cur-

rent path to a separate loop that does not interfere with

the more sensitive analog control function. These two

grounds must be connected together on the PC board

layout at a single point.

IRU3138CS Datasheet(PDF) 12 Page - International Rectifier