178021501 Datasheet, PDF (20/32 Pages) Wurth Elektronik GmbH & Co. KG, Germany. – MagI³C Power Module Product Family VDRM - Variable Step Down Regulator Module

171021501/WPMDU1251501NT
MagI³C Power Module Product Family
VDRM - Variable Step Down Regulator Module
Step G. Light load behaviour
The MagI³C Power Module is a non-synchronous converter. One of the characteristics of a non-synchronous
converter is that as the load current on the output is decreased, a point is reached where the energy delivered by
a single switching pulse is more than the load can absorb. This causes the output voltage to rise slightly. This rise
in output voltage is sensed by the feedback loop and the device responds by skipping one or more switching
cycles until the output voltages falls back to the set point. At very light loads or no load, many switching cycles are
skipped. The observed effect during this pulse skipping mode of operation is an increase in the peak to peak
ripple voltage, and a decrease in the ripple frequency. The load current at which pulse skipping begins is a
function of the input voltage, the output voltage, and the switching frequency. A plot of the pulse skipping
threshold current as a function of input voltage is given in Figure 14 for a number of popular output voltage and
switching frequency combinations.
900
800
2.5V/400kHz
3.3V/400kHz
700
5.0V/400kHz
9V/600kHz
600
12V/800kHz
15V/1MHz
500
400
300
200
100
0
10 15 20 25 30 35 40 45 50
Input Voltage (V)
27D
Figure 14. Pulse Skipping Load Threshold
Step H. Electromagnetic Interference
100
90
EN 55022 Class A
EN 55022 Class B
80
EMI Vertical
EMI Horizontal
70
60
50
40
30
20
10
0
30
100
Freqency (MHz)
1000
24D
Figure 15. Radiated Emissions EN55022 complaint: VIN = 24V; VOUT = 5V ; Load 2A
Data Sheet
©2014
Würth Elektronik eiSos GmbH & Co. KG - REV 0.1
PRELIMINARY
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