NMA 5V, 12V & 15V Series
Isolated 1W Dual Output DC/DC Converters
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 NMA series of DC/DC converters are all 1ꢀꢀ% production tested at their stated isolation voltage. This is 1kVDC for 1 second.
A question commonly asked is, “What is the continuous voltage that can be applied across the part in normal operation?”
For a part holding no specific agency approvals, such as the NMA series, both input and output should normally be maintained within SELV limits i.e. less than ±2.±V peak, or
6ꢀVDC. 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 NMA 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 2ꢀ% 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.
RoHS COMPLIANT INFORMATION
This series is compatible with RoHS soldering systems with a peak wave solder temperature of
3ꢀꢀ°C for 1ꢀ seconds. The pin termination finish on the SIP package type is Tin Plate, Hot Dipped
over Matte Tin with Nickel Preplate. The DIP types are Matte Tin over Nickel Preplate. Both types in
this series are backward compatible with Sn/Pb soldering systems.
For further information, please visit www.murata-ps.com/rohs
APPLICATION NOTES
Minimum load
The minimum load to meet datasheet specification is 1ꢀ% of the full rated load across the specified input voltage range. Lower than 1ꢀ% 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 1ꢀμF, are shown in the table below. The product
series will start into a capacitance of ±7μF with an increased start time, however, the maximum recommended output capacitance is 1ꢀμF.
Typical Start-Up Wave Form
Start-up time
μs
Start-up time
μs
NMAꢀ5ꢀ5xC
NMAꢀ5ꢀ9xC
NMAꢀ512xC
NMAꢀ515xC
NMA12ꢀ5xC
NMA12ꢀ9xC
2ꢀ18
NMA1212xC
NMA1215xC
NMA15ꢀ5xC
NMA1512xC
NMA1515xC
9765
661ꢀ
1598ꢀ
1ꢀ6ꢀ
1±52ꢀ
2ꢀ2ꢀꢀ
1ꢀ61
1627
6275
3935
www.murata-ps.com/support
KDC_NMA.G02 Page 3 of 6
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