Technical enquiries email: mk@murata-ps.com, tel: +44 (0)1908 615232

MTU1 Series

Isolated 1W Single Output SM DC/DC Converters

2011-02-01

KDC_MTU.A03 Page 2 of 6

www.murata-ps.com

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 MTU1 series of DC/DC converters are all 100% 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 MTU1 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 MTU1 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.

1. Measured on centre of input side PCB.

TEMPERATURE DERATING GRAPH

150

100

50

0

-40

0

0.5

1.0

1.5

Safe Operating Area

85°C

Ambient Temperature (°C)

RoHS COMPLIANCE INFORMATION

This series is compatible with RoHS soldering systems with a peak reflow solder temperature of 245ºC as per J-STD-020D.

The pin termination finish on this product series is Matte Tin over Nickel Preplate. The series is backward compatible with Sn/Pb soldering

systems. The series has a Moisture Sensitivity Level (MSL) 1.

Samples of the product series were tested in accordance with the conditioning described for MSL level 1 in IPS/JEDEC STD-020D.

The product series passed electrical tests and visual inspection criteria.

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

TOLERANCE ENVELOPES

The voltage tolerance envelope shows typical load regulation characteristics for this product series. The tolerance

envelope is the maximum output voltage variation due to changes in output loading.

Output Load Current (%)

5%

0%

-4%

1%

100

75

50

25

10

Output Load Current (%)

5.5%

0%

-4%

1.5%

100

75

50

25

10

5V output types

All other types