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 41/48
EVALUATION BOARD SCHEMATIC (178040302 v1.0)
The board schematic has been developed to be suitable for all conditions of input and output voltage, switching frequency,
load current and to achieve optimum load transient response.
The two 47µF multi-layer ceramic capacitors (MLCCs) at the input handle the switching current ripple and support fast load
transients preventing the voltage at the VIN pin from dropping, potentially below the UVLO. Two MLCCs in parallel helps
reducing further the ESR. The additional 220 µF aluminum electrolytic polymer capacitor is mounted as termination of the
supply line and provides a damping of possible oscillations due to the series resonance circuit represented by the
inductance of the supply line and the input capacitance.
The output capacitors should provide a high value of capacitance as well as a low ESR, in order to reduce the output voltage
ripple and improving load transient response. This is achieved in this evaluation board by combining two 47µF MLCCs with a
220 µF aluminum electrolytic polymer capacitor. The use of two MLCCs in parallel leads to a further reduction of the ESR.
Furthermore the use of two parallel MLCCs at the input and at the output increases the reliability of the system.
VIN VO UT
ENABLE
SS/TRK
INTSS
RT/CLK
R
RT
R
SET
FB
AG ND
PG ND
V
IN
V
OUT
PG VSENSE+
27
28
6
7
4
36
35
+
C
IN1
220µF
C
IN2
47µF
C
IN3
47µF
C
OU T1
47µF
C
OUT2
47µF
+
C
OU T3
220µF
470pF 1kΩ
301R
LED1
R
UVL O
C
SS
IC1
R1
C
SYNC
R
SYNC
Operational Requirements
At small V
IN
to V
OUT
ratio (high duty cycle) the input current will be in a similar range than the output current. Make sure that
your supply for the module is capable of high currents (check current limit setting of your power supply). In case your module
output voltage V
OUT
is set to very low values (for example 0.8V) electronic loads might not be able to work correctly. Use
discrete high power resistors instead as a load. Use thick and short leads to the input of the module and to the load. High
currents result in additional voltage drops across the cables which decrease the voltage at the load. Measure the input and
output voltage directly at the ceramic capacitors at the input and output (test points).