Datasheet
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© May 2016
Würth Elektronik eiSos GmbH & Co. KG - Data Sheet - REV 1.0
17/46
WPMDU1251501 / 171021501
MagI³C Power Module
VDRM - Variable Step Down Regulator Module
Step 4 Select output capacitor (C
OUT
)
L
C
OUT
Rload
V
IN
V
OUT
I
L
I
out
HS Mosfet
ESR
V
ESR
V
COUT
LS Mosfet
C
IN
None of the required output capacitors is integrated within the module. . At a minimum, the output capacitor must meet the
worst case RMS current rating of
, as calculated in equation (4).
Beyond that, additional capacitance will reduce output ripple as long as the ESR is low enough to permit it. There is no
limit of the maximum output capacitance. Please consider the derating of the nominal capacitance value due to
temperature, aging and applied DC voltage (only for MLCC, e.g. X7R up to -50%).
Selection by output voltage ripple requirements
The capacitor should be selected in order to minimize the output voltage ripple and provide a stable voltage at the output.
Under steady state conditions, the voltage ripple observed at the output can be defined as:
Very low ESR capacitors, like ceramic and polymer electrolytic, are recommended. If a low ESR capacitor is selected, the
equation (4) can be simplified and a first condition for the minimum capacitance value can be derived: