Datasheet

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© May 2016
Würth Elektronik eiSos GmbH & Co. KG - Data Sheet - REV 1.0
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WPMDU1251501 / 171021501
MagI³C Power Module
VDRM - Variable Step Down Regulator Module
PCB Layout Instructions:
PC board layout is an important part of DC-DC converter design. Poor board layout can disrupt the performance of a DC-
DC converter and surrounding circuitry by contributing to EMI, ground bounce and resistive voltage drop in the traces.
These can send erroneous signals to the DC-DC converter resulting in poor regulation or instability. Good layout can be
implemented by following five simple design rules.
1: Minimize area of switched current loops
C
IN
VIN
PGND
VOUT
Power Module
C
OUT
Loop 1
Loop 2
High
di/dt
V
IN
V
OUT
Target is to identify the paths in the system which have discontinuous current flow. They are the most critical ones because
they act as an antenna and cause observable high frequency noise (EMI). The easiest approach to find the critical paths
is to draw the high current loops during both switching cycles and identify the sections which do not overlap. They are the
ones where no continuous current flows and high di/dt is observed. Loop 1 is the current path during the ON-time of the
High-Side MOSFET. Loop 2 is the current path during the OFF-time of the High-Side MOSFET.
V
IN
VIN
FB
PGND
VOUT
Module
R
SET
C
OUT
AGND
C
IN
V
OUT
Based on those considerations, the path of the input capacitor C
IN
is the most critical one to generate high frequency noise
on Vin. Therefore place C
IN
as close as possible to the MagI³C power module V
IN
and PGND pins. This will minimize the
high di/dt area and reduce radiated EMI. Additionally, grounding for both the input and output capacitor should consist of
a localized top side plane that connects to the PGND pins.