Delta Electronics S48SR - Manual (Page 8)

DS_S48SR12001_07052006
8
Do not ground one of the input pins without grounding
one of the output pins. This connection may allow a
non-SELV voltage to appear between the output pin
and ground.
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 1A maximum rating to
be installed in the ungrounded lead. A lower ratd 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.
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 10 to 100 µF
electrolytic capacitor (ESR < 0.7 Ω at 100 kHz)
mounted close to the input of the module to improve
the 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 if the system in
which the power module is to be used must meet
safety agency requirements.
When the input source is 60Vdc or below, 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 any
hazardous voltages, including the ac mains, with
reinforced insulation.
One Vi pin and one Vo pin are grounded, or all
the input and output pins are kept floating.
The input terminals of the module are not operator
accessible.
A SELV reliability test is conducted on the system
where the module is used to ensure that under a
single fault, hazardous voltage does not appear at
the module’s output.