E24SR Datasheet, PDF (7/14 Pages) Delta Electronics, Inc. – Fixed frequency operation

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. Below is the reference design
for an input filter tested with E24SR12005XXXX to meet
class B in CISSPR 22.
Schematic and Components List
Cin is 100uF*2 low ESR Aluminum cap;
CX is 2.2uF ceramic cap;
CY1 are 10nF ceramic caps;
CY2 are 10nF ceramic caps;
CY is 1nF ceramic cap;
L1 is common-mode inductor, L1=0.53mH;
Test Result: Vin=24V, Io=5A,
Yellow line is quasi peak mode; Blue line is average mode
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 15A 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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