Data Sheet MW005-Series Power Modules:
April 1999 36 Vdc to 75 Vdc Inputs; 5 W
Tyco Electronics Corp. 13
Safety Considerations
For safety-agency approval of the system in which the
power module is used, the power module must be
installed in compliance with the spacing and separation
requirements of the end-use safety agency standard,
i.e.,
UL
1950,
CSA
C22.2 No. 950-95, and VDE 0805
(EN60950, IEC950).
If the input source is non-SELV (ELV or a hazardous
voltage greater than 60 Vdc and less than or equal to
75 Vdc), for the module's output to be considered
meeting the requirements of safety extra-low voltage
(SELV), all of the following must be true:
■The input source is to be provided with reinforced
insulation from any other hazardous voltages, includ-
ing the ac mains; and
■One VI pin and one V O pin are to be grounded or both
the input and output pins are to be kept floating; and
■The input pins of the module are not operator acces-
sible; and
■Another SELV reliability test is conducted on the
whole system, as required by the saf ety agencies, on
the combination of supply source and the subject
module to verify that under a single fault, hazardous
voltages do not appear at the module's output.
Note: Do not ground either of the input pins of the
module without grounding one of the output
pins. This may allow a non-SELV voltage to
appear between the output pins and ground.
The power module has extra-low v oltage (ELV) outputs
when all inputs are ELV.
The input to these units is to be provided with a maxi-
mum 5 A normal-blow fuse in the ungrounded lead.
Feature Descriptions
Overcurrent Protection
To provide protection in a fault (output overload) condi-
tion, the unit is equipped with internal current-limiting
and can endure current limiting for an unlimited dura-
tion. At the point of current-limit inception, the unit
shifts from voltage control to current control. If the out-
put voltage is pulled very low during a severe fault, the
current-limit circuit can exhibit either foldback or tailout
characteristics (output current decrease or increase).
The unit operates normally once the output current is
brought back into its specified range.
Output Overvoltage Protection
The output overvoltage clamp consists of control cir-
cuitry, independent of the primary regulation loop, that
monitors the voltage on the output terminals. The con-
trol loop of the clamp has a higher voltage set point
than the primary loop (see Feature Specifications
table). This provides a redundant voltage control that
reduces the risk of output overvoltage.
Thermal Considerations
To maintain the full power rating at ambient tempera-
tures above 70 °C (TA > 70 °C), add an external capac-
itor across the input close to the power module input
leads. Use an 80 V capacitor with a minimum ripple
current rating of 160 mArms and maximum impedance
of 1.0 Ω at 105 °C and 100 kHz. Otherwise, derate the
output power as shown in Figure 28.
8-548(C)
Figure 28. Thermal Derating Cur ve
AMBIENT TEMPERATURE, T
A
(°C)
OUTPUT POWER, P
O
(W)
5.0
4.5
4.0
0.0
–40
1.0
3.5
3.0
2.5
2.0
1.5
0.5
–20 0 20 40 8570
WITH EXTERNAL
CAPACITOR
WITHOUT EXTERNAL
CAPACITOR