CRE1 Series

Isolated 1W Single Output Isolated DC-DC Converters

KDC_CRE1.E01 Page 3 of 17

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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 CRE1 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?”

The CRE1 series, through hole variants (excluding surface mount variants) have been recognised 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 CRE1 series has toroidal isolation transformers, with no additional insulation between primary and secondary windings of enamelled 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 recognised 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.

SAFETY APPROVAL

The CRE1 series has been recognised by Underwriters Laboratory (UL) to UL60950 for functional insulation in a maximum still air ambient temperature of 100°C for the C versions

and 130°C for the 3C versions as measured on the case of the unit (hotspot). The CRE1S0505MC is not currently UL recognised.

The CRE1 series of converters are not internally fused so to meet the requirements of UL60950 an anti-surge input line fuse should always be used with ratings as defined below.

CRE1S03xxS3C: 1A

CRE1S05xxxxC: 0.7A

CRE1S12xxSC: 0.2A

CRE1S24xxSC: 0.16A

All fuses should be UL recognised, 125V rated.

File number E151252 applies.

RoHS COMPLIANCE and MSL INFORMATION

The Through Hole parts (SIP/DIP) in this series are compatible with RoHS soldering systems with a peak wave solder temperature of 260°C for

10 seconds. Please refer to application notes for further information. 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. This series is backward compatible with Sn/Pb soldering

systems.

The Surface Mount parts (MC/MEC) in this series are compatible with RoHS soldering systems as per J-STD-020D.1 The pin termination finish

on the Surface Mount package types is Matte Tin over Nickel Preplate. This series is backward compatible with Sn/Pb soldering systems. The

Surface Mount parts have a Moisture Sensitivity Level (MSL) 1.

Samples of the Surface Mount parts were tested in accordance with the conditioning described for MSL level 1 in IDC/J-STD-020D.1. The

products passed electrical tests and visual inspection criteria.

For further information, please visit www.murata-ps.com/rohs