NPH25S2415IC Datasheet, PDF (5/8 Pages) Murata Manufacturing Co., Ltd. – Isolated 25W Single Output DC/DC Converters

NPH25S Series
Isolated 25W Single Output DC/DC Converters
EMC FILTERING AND SPECTRA
FILTERING
The module includes a basic level of filtering, sufficient for many applications. Where lower noise levels are desired, filters can easily be added to achieve any required
noise performance.
A DC/DC converter generates noise in two principle forms: that which is radiated from its body and that conducted on its external connections. There are three separate
modes of conducted noise: input differential, output differential and input-output.
This last appears as common mode at the input and the output, and cannot therefore be removed by filtering at the input or output alone. The first level of filtering is to
connect a capacitor between input and output returns, to reduce this form of noise. It typically contains high harmonics of the switching frequency, which tend to appear
as spikes on surrounding circuits. The voltage rating of this capacitor must match the required isolation voltage. (Due to the great variety in isolation voltage and required
noise performance, this capacitor has not been included within the converter.)
Input ripple is a voltage developed across the internal Input decoupling capacitor. It is therefore measured with a defined supply source impedance. Although simple series
inductance will provide filtering, on its own it can degrade the stability. A shunt capacitor is therefore recommended across the converter input terminals, so that it is fed
from a low impedance.
If no filtering is required, the inductance of long supply wiring could also cause a problem, requiring an input decoupling capacitor for stability. An electrolytic will perform
well in these situations. The input-output filtering is performed by the common-mode choke on the primary. This could be placed on the output, but would then degrade the
regulation and produce less benefit for a given size, cost, and power loss.
Radiated noise is present in magnetic and electrostatic forms. The latter is suppressed by the metal case, which is connected to the output return, typically a zero-volt
point. Thanks to the small size of these units, neither form of noise will be radiated “efficiently”, so will not normally cause a problem. Any question of this kind usually
better repays attention to conducted signals.
EMC FILTER AND VALUES TO OBTAIN SPECTRA AS SHOWN
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NPH25S2403
C1
10μF 100V
C2
2.2μF 63V
C3
47μF 63V
Component reference
C4
L1
10μF 25V
NPH25S2405
10μF 100V
2.2μF 63V
47μF 63V
10μF 25V
NPH25S2412
10μF 100V
2.2μF 63V
Not required
10μF 25V
NPH25S2415
10μF 100V
2.2μF 63V
47μF 63V
10μF 25V
NPH25S4803
10μF 100V
Not required
Not required
10μF 25V
NPH25S4805
10μF 100V
Not required
Not required
10μF 25V
NPH25S4812
10μF 100V
Not required
Not required
10μF 25V
NPH25S4815
10μF 100V
Not required
Not required
10μF 25V
C1, C2 & C4 : Electrolytic capacitors
C3 : Polyester or ceramic capacitor
EMC Spectra red limit line is EN 55022 curve B Quasi-peak average limit.
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L2
MPS 18R333C
33μH 2A
MPS 18R333C
33μH 2A
MPS 18R333C
33μH 2A
MPS 18R333C
33μH 2A
MPS 18R104C
100μH 1.2A
MPS 18R104C
100μH 1.2A
MPS 18R104C
100μH 1.2A
MPS 18R104C
100μH 1.2A
L3
4.7μH
10μH
MPS 49330C
33μH 2.5A
MPS 18R333C
33μH 2.00A
4.7μH
10μH
MPS 49330C
33μH 2.5A
MPS 18R333C
33μH 2.00A
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