171020601 查看數據表（PDF） - Wurth Elektronik GmbH & Co. KG, Germany.

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171020601

MagI3C Power Module VDRM – Variable Step Down Regulator Module

Wurth Elektronik GmbH & Co. KG, Germany. 

WPMDM1500602 / 171050601

MagI3C Power Module

VDRM – Variable Step Down Regulator Module

Step 3 Select the output capacitor (COUT)

HS Mosfet

L

IL

IOUT

VIN

CIN

LS Mosfet

VCOUT

VES R

COUT

ES R

VOUT Rload

None of the required output capacitors are integrated within the module. A general recommendation in order to guarantee a

stable behavior is to place at least 200µF at the output.The output capacitor must meet the worst case RMS current rating of

0.5·∆IL, as calculated by equation (5).

ICOUTRMS

=

∆IL

√12

(5)

where ∆IL is the inductor current ripple calculated with the equation (6):

∆IL=

VOUT∙(VIN − VOUT)

fSW ∙ L∙VIN

(6)

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:

1

VOUT ripple = ∆IL∙ESR+∆IL∙ 8∙fSW∙COUT

(7)

Very low ESR capacitors, like ceramic and polymer electrolytic, are recommended. If a low ESR capacitor is selected,

equation (7) can be simplified and a first condition for the minimum capacitance value can be derived:

COUT

≥

∆IL

8∙VOUT ripple ∙ fSW

(8)

Beyond that, additional capacitance will reduce output ripple as long as the ESR is low enough to permit it. 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%).

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© July 2018

Würth Elektronik eiSos GmbH & Co. KG – Data Sheet Rev. 2.0

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