Datasheet

DS_
T48SR3R307_10162012
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 100µF electrolytic
capacitor mounted close to the input of the module to
improve the stability.
Module internal input filter is only one 1uF ceramic cap,
not L-C filter or Pi filter, so the external input cap ESR
loss need be paid more attention. A external inductor
(1uH) placed in front of module can decrease ESR loss
of the external input cap.
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 T48SR3R307XXXX
to meet EN55022 (VDE0878) class A(both q. peak and
average)
Schematic and Components List
Figure 16 : Capacitive and inductive EMI Filter
C1=47uF /100 V(Low ESR)
C2=C3= 47 uF/100 V(Low ESR)
C4=C5=2200pF
T1=0.59mH type P0353 (Pulse)
Test Result:
At T = +25°C , Vin = 48 V and Io=7.5 A
Blue line is quasi peak mode; Green line is average
mode.
Figure 17: EMI test negative line @ T = +25 ° C and Vin = 48 V
Figure 18: EMI test positive line @ T = +25 ° C and Vin = 48 V
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., UL60950-1, CSA C22.2 NO.
60950-1 2nd and IEC 60950-1 2nd : 2005 and EN 60950-1
2nd: 2006+A11+A1: 2010, 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: