DESIGN CONSIDERATIONS

Input Source Impedance

The impedance of the input source connecting to the DC/DC power

modules will interact with the modules and affect the stability. A low

ac-impedance input source is recommended. If the source

inductance is more than a few μH, we advise adding a typical

stability.

Layout and EMC Considerations

Delta’s DC/DC power modules are designed to operate in a

wide variety of systems and applications. For design

assistance with EMC compliance and related PWB layout

issues, please contact Delta’s technical support team. An

external input filter module is available for easier EMC

compliance design. Application notes to assist designers in

addressing these issues are pending release.

Safety Considerations

The power module must be installed in compliance with the

spacing and separation requirements of the end-user’s

safety agency standard, i.e., UL60950, CAN/CSA-C22.2 No.

60950-00 and EN60950: 2000 and IEC60950-1999, if the

system in which the power module is to be used must meet

safety agency requirements.

Basic insulation based on 75 Vdc input is provided between

the input and output of the module for the purpose of

applying insulation requirements when the input to this

DC-to-DC converter is identified as TNV-2 or SELV. An

additional evaluation is needed if the source is other than

TNV-2 or SELV.

When the input source is SELV circuit, the power module

meets SELV (safety extra-low voltage) requirements. If the

input source is a hazardous voltage which is greater than 60

Vdc and less than or equal to 75 Vdc for the module’s output

to meet SELV requirements, all of the following must be met:

The input source must be insulated from the ac

mains by reinforced or double insulation.

The input terminals of the module are not

operator accessible.

If the metal baseplate is grounded, one Vi pin and

one Vo pin shall also be grounded.

A SELV reliability test is conducted on the system

where the module is used, in combination with the

module, to ensure that under a single fault,

hazardous voltage does not appear at the

module’s output.

When installed into a Class II equipment (without

grounding), spacing consideration should be given to

the end-use installation, as the spacing between the

module and mounting surface have not been

evaluated.

The power module has extra-low voltage (ELV)

outputs when all inputs are ELV.

This power module is not internally fused. To achieve

optimum safety and system protection, an input line

fuse is highly recommended. The safety agencies

require a normal-blow fuse with 50A maximum rating

to be installed in the ungrounded lead. A lower rated

fuse can be used based on the maximum inrush

transient energy and maximum input current.

Soldering and Cleaning Considerations

Post solder cleaning is usually the final board

assembly process before the board or system

undergoes electrical testing. Inadequate cleaning

and/or drying may lower the reliability of a power

module and severely affect the finished circuit board

assembly test. Adequate cleaning and/or drying is

especially important for un-encapsulated and/or open

frame type power modules. For assistance on

appropriate soldering and cleaning procedures,

please contact Delta’s technical support team.

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