Datasheet

CME Series
Isolated 0.75W Single Output Isolated DC/DC Converters
KDC_CME.A04 Page 2 of 7
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TEMPERATURE CHARACTERISTICS
Parameter Conditions Min. Typ. Max. Units
Specification All output types -40 85
°C
Storage -50 130
Case temperature rise above
ambient
3.3V & 5V output types 41
12V output types
32
Cooling Free air convection
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 CME series of DC/DC converters are all 100% production tested at their stated isolation voltage. This is 1kVDC for 1 second for C versions and 3kVDC for 1
second for 3C versions.
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 CME series, 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 CME 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