Delta Electronics Series H48SA - Manual (Page 7)

DS_H48SA12025_05052008
7
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 33 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
H48SA12025NN A to meet class B in CISSPR 22.
Schematic and Components List
CX
CY1
CY1
CX1
Vin(+)
Vin(-)
Vo(+)
Vo(-)
LOAD H48SA12025
Cin
+
-
Vin
L1 L2
CY
CX is 4.7uF ceramic cap;
CX1 is 4.7uF ceramic cap;
CY is 3.3nF ceramic cap;
CY1 is 4.7nF ceramic cap;
L1 is common-mode inductor, L1=0.08mH;
L2 is common-mode inductor, L1=0.24mH;
Test Result
Test result is in compliance with CISPR 22 class B, which
is shown as below:
Vin=48V, Io=25A,
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. When the input source is 60 Vdc 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:
Š The input source must be insulated from any
hazardous voltages, including the ac mains, with
reinforced insulation.
Š One Vi pin and one Vo pin are grounded, or all the
input and output pins are kept floating.
Š The input terminals of the module are not operator
accessible.
Š If the metal baseplate is grounded the output must
be also grounded.
Š 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.
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. 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 fuse with
30A 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.