WPMDH1100601 / 171010601
MagI3C Power Module
VDRM – Variable Step Down Regulator Module
EVALUATION BOARD SCHEMATIC (178010601 v3.1)
The evaluation board schematic has been developed to be suitable for all input and output voltage conditions, switching
frequencies and load currents as well as to achieve optimum load transient response.
Lf
IC1
1
7
VIN
VIN
VOUT
VOUT
R19
RFBT
CFF
RON
Module
2
3
6
4
RON
EN
FB
+ C6
+
C5
C4
RENT
Cf
C2
C1
C3
AGND
PGND
EP
SS
5
RENB
CSS
RFBB
GND
GND
Optional
Optional
Optional input filter
The two multi-layer ceramic capacitors (MLCCs) C2 and C3 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 threshold. Two MLCCs in
parallel helps to reduce the ESR. The additional aluminum electrolytic capacitor C1 is only for evaluation board protection
purpose. It is mounted as termination of the supply line and provides a slight damping of possible oscillations of the series
resonance circuit represented by the inductance of the supply line and the input capacitance.
The additional MLCC Cf is part of the input filter and is mounted on the board. The inductor Lf instead is not mounted and
replaced by the zero ohm resistor R19. In case the input filter is placed, R19 must be removed and an appropriate Lf
mounted.
The output capacitors should provide a low ESR, in order to reduce the output voltage ripple. The requirement of high
capacitance for good transient response performance is fulfilled by mounting an additional aluminum polymer capacitor C6
in parallel to the MLCC output capacitors. The use of two MLCCs in parallel leads to a very low total ESR. Furthermore, the
use of more MLCCs in parallel at the input and at the output increases the reliability of the system (in case one capacitor
fails, there is still another one remaining).
Operational Requirements
At high duty cycles (VIN very close to VOUT) the input current will be very similar to the output current. Make sure that your
supply for the module is capable of delivering high enough currents (check the current limit setting of your power supply). In
case your module output voltage VOUT 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).
In order to have a constant switching frequency of 500kHz, put the jumper of RON on the same line of the jumper of the
selected VOUT (see below).
RON
VOUT
RON
VOUT
selection
selection
selection
selection
90k9
75k0
49k9
37k4
27k4
18k2
ADJ
6V
5V
90k9
75k0
49k9
37k4
27k4
18k2
ADJ
6V
5V
3.3V
2.5V
1.8V
1.2V
ADJ
3.3V
2.5V
1.8V
1.2V
ADJ
That corresponds to fSW = 500kHz
That DOES NOT correspond to fSW = 500kHz
we-online.com
Würth Elektronik eiSos GmbH & Co. KG – Data Sheet Rev. 1.0
© September 2017
45/54
WURTH [ WURTH ELEKTRONIK GMBH & CO. KG, GERMANY. ]
