NMH Series
Isolated 2W Dual Output DC/DC Converters
KDC_NMH.F01 Page 4 of 6
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APPLICATION NOTES (continued)
Ripple & Noise Characterisation Method
Ripple and noise measurements are performed with the following test configuration.
C1 1µF X7R m ultilayer ceramic capacitor, voltage rating to be a minimum of 3 times the output voltage of the DC/DC converter
C2
10µF tantalum capacitor, voltage rating to be a minimum of 1.5 times the output voltage of the DC/DC converter with an ESR of less
than 100m at 100 kHz
C3 100nF multilayer ceramic capacitor, general purpose
R1 450 resistor, carbon film, ±1% tolerance
R2 50 BNC termination
T1 3T of the coax cable through a ferrite toroid
RLOAD Resistive load to the maximum power rating of the DC/DC converter. Connections should be made via twisted wires
Measured values are multiplied by 10 to obtain the specified values.
Differential Mode Noise Test Schematic
OUTPUT RIPPLE REDUCTION
By using the values of inductance and capacitance stated, the output ripple at the rated load is lowered to 5mV p-p max.
Component selection
Capacitor: Ceramic chip capacitors are recommended. It is required that the ESR (Equivalent Series Resistance) should be as low as possible, X7R types are recommended.
The voltage rating should be at least twice (except for 15V output), the rated output voltage of the DC/DC converter.
Inductor: The rated current of the inductor should not be less than that of the output of the DC/DC converter. At the rated current, the DC resistance of the inductor should be
such that the voltage drop across the inductor is <2% of the rated voltage of the DC/DC converter. The SRF (Self Resonant Frequency) should be >20MHz.
OSCILLOSCOPE
Y INPUT
SUPPLY
C1 C2 C3 R1 T1
R2
Input Output
DC/DC Converter
R LOAD
+
+
-
-
DC
DC
L
C
Load
Power
Source
Order Code L (µH)
Inductor Order Codes
C (µF)
SMD Through Hole
NMH0505XC 47 82473C 11R473C 4.7
NMH0509XC 47 82473C 11R473C 2.2
NMH0512XC 150 82154C 11R154C 3.3
NMH0515XC 100 82104C 11R104C 3.3
NMH1205XC 47 82473C 11R473C 4.7
NMH1209XC 47 82473C 11R473C 2.2
NMH1212XC 150 82154C 11R154C 3.3
NMH1215XC 100 82104C 11R104C 3.3
NMH2405XC 47 82473C 11R473C 4.7
NMH2409XC 47 82473C 11R473C 2.2
NMH2412XC 150 82154C 11R154C 3.3
NMH2415XC 100 82104C 11R104C 3.3
NMH4805XC 47 82473C 11R473C 4.7
NMH4809XC 47 82473C 11R473C 2.2
NMH4812XC 150 82154C 11R154C 3.3
NMH4815XC 100 82104C 11R104C 3.3
Product specification for MPS inductors can be found at:
1100R Series (Through Hole)
http://www.murata-ps.com/data/magnetics/kmp_1100r.pdf
8200 Series (SMD)
http://www.murata-ps.com/data/magnetics/kmp_8200c.pdf
