Datasheet

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Würth Elektronik eiSos GmbH & Co. KG - Data Sheet - REV 1.0
18/31
WPMDH1302401 / 171032401
MagI³C Power Module
VDRM - Variable Step Down Regulator Module
DESIGN FLOW
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. Loop1 is the current path
during the ON-time of the High-Side Mosfet. Loop2 is the current path during the OFF-time of the High-Side Mosfet.
V
IN
VIN
FB
PGND
VOUT
Module
R
FBT
R
FBB
C
OUT
AGND
6
7
C
IN
1
EP 4
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 exposed pad EP.
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 exposed pad.