Datasheet
NMV 5V, 12V & 15V Series
3kVDC Isolated 1W Single & Dual Output DC/DC Converters
KDC_NMV.H01 Page 3 of 6
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TECHNICAL NOTES
ISOLATION VOLTAGE
‘Hi Pot Test’, ‘Flash Tested’, ‘Withstand Voltage’, ‘Proof Voltage’, ‘Dielectric Withstand Voltage’ & ‘Isolation Test Voltage’ are all terms that relate to the same thing, a test voltage,
applied for a specified time, across a component designed to provide electrical isolation, to verify the integrity of that isolation.
Murata Power Solutions NMV series of DC/DC converters are all 100% production tested at their stated isolation voltage. This is 3kVDC for 1 minute.
A question commonly asked is, “What is the continuous voltage that can be applied across the part in normal operation?”
The NMV has been recognized by Underwriters Laboratory for functional insulation, both input and output should normally be maintained within SELV limits i.e. less than 42.4V
peak, or 60VDC. The isolation test voltage represents a measure of immunity to transient voltages and the part should never be used as an element of a safety isolation system.
The part could be expected to function correctly with several hundred volts offset applied continuously across the isolation barrier; but then the circuitry on both sides of the barrier
must be regarded as operating at an unsafe voltage and further isolation/insulation systems must form a barrier between these circuits and any user-accessible circuitry according
to safety standard requirements.
REPEATED HIGH-VOLTAGE ISOLATION TESTING
It is well known that repeated high-voltage isolation testing of a barrier component can actually degrade isolation capability, to a lesser or greater degree depending on materials,
construction and environment. The NMV series has toroidal isolation transformers, with no additional insulation between primary and secondary windings of enameled wire. While
parts can be expected to withstand several times the stated test voltage, the isolation capability does depend on the wire insulation. Any material, including this enamel (typically
polyurethane) is susceptible to eventual chemical degradation when subject to very high applied voltages thus implying that the number of tests should be strictly limited. We
therefore strongly advise against repeated high voltage isolation testing, but if it is absolutely required, that the voltage be reduced by 20% from specified test voltage.
This consideration equally applies to agency recognized parts rated for better than functional isolation where the wire enamel insulation is always supplemented by a further
insulation system of physical spacing or barriers.
APPLICATION NOTES
Minimum load
The minimum load to meet datasheet specification is 10% of the full rated load across the specified input voltage range. Lower than 10% minimum loading will result in
an increase in output voltage, which may rise to typically double the specified output voltage if the output load falls to less than 5%.
Capacitive loading and start up
Typical start up times for this series, with a typical input voltage rise time of 2.2µs and output capacitance of 10µF, are shown in the table below. The product
series will start into a capacitance of 47µF with an increased start time, however, the maximum recommended output capacitance is 10µF.
Typical Start-Up Wave Form
Start-up time Start-up time
µs µs
NMV0505xC 1966 NMV1212xC 8650
NMV0509xC 5360 NMV1215xC 11171
NMV0512xC 11180 NMV1505xC 803
NMV0515xC 16270 NMV1512xC 3510
NMV1205xC 1290 NMV1515xC 8361
NMV1209xC 4140
SAFETY APPROVAL
The NMV series has been recognized by Underwriters Laboratory (UL) to UL 60950 for functional insulation.
The NMV Series of converters are not internally fused so to meet the requirements of UL 60950 an anti-surge input line fuse should always be used with ratings as defined below.
NMV05xxxxC: 0.315A
NMV12xxxxC: 1A
NMV15xxxxC: 1A
All fuses should be UL recognized and rated to at least the maximum allowable DC input voltage.
File number E151252 applies.