Datasheet

WPMDB1400362Q / 171040302
MagI
3
C Power Module
VDRM – Variable Step Down Regulator Module
we-online.com Würth Elektronik eiSos GmbH & Co. KG – Data Sheet Rev. 1.0
© May 2016 36/48
LAYOUT RECOMMENDATION
PCB layout is an important part of DC-DC converter design. Poor board layout can interfere with 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
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.
Based on those considerations, the path of the input capacitor C
IN
is the most critical one to generate high frequency noise
on V
IN
. 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.