Datasheet
Data Sheet
©2013
Würth Elektronik eiSos GmbH & Co. KG - REV 0.2
PRELIMINARY
12/ 23
171020601/WPMDH1200601J
MagI³C Power Module Product Family
VDRM - Variable Step Down Regulator Module
J CIRCUIT DESCRIPTION
Following is a typical waveform showing the boundary condition.
Transition Mode Operation
V
IN
= 24V, V
OUT
= 3.3V, I
OUT
= 0.35A
2 µs/Div
500 mA/Div
V
OUT
=3.3V
The inductor internal to the module is 10μH. This value was chosen as a good balance between low and high input
voltage applications. The main parameter affected by the inductor is the amplitude of the inductor ripple current (I
LR
).
I
LR
can be calculated with:
(16)
Where V
IN
is the maximum input voltage and f
SW
is determined from equation (10).
If the output current I
OUT
is determined by assuming that I
OUT
= I
L
, the higher and lower peak of I
LR
can be determined.
Be aware that the lower peak of I
LR
must be positive if CCM operation is required.
Step 7. Select Feed Forward Capacitor (Cff)
As worst case, assume the gain of A
FB
with the C
FF
capacitor at the switching frequency is 1. The selected capacitor
should have sufficient voltage and RMS current rating.
The feed forward capacitor C
FF
, should be located close to the FB pin.
Select Power Loss and Board thermal Requirements
For example:
the device must see a maximum junction-to-ambient thermal resistance of:
(17)
Given the typical thermal resistance from junction to case to be 1.9 °C/W. Use the 85°C power dissipation curves in
the Typical Performance Characteristics section to estimate the PIC-LOSS for the application being designed. In this
application it is 1.5W.