iru3137 International Rectifier Corp., iru3137 Datasheet - Page 12

• Manufacturer Part Number: iru3137
• Description: 8-pin Synchronous Pwm Controller
• Manufacturer: International Rectifier Corp.

IRU3137
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
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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.
Rev. 1.0
06/22/04