1010 Tyco Electronics Corp..
Data Sheet
July 2002dc-dc Converters; 36 to 75 Vdc Input, 3.3 Vdc Output; 165 W to 198 W
FW250F1 and FW300F1 Power Modules:
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
(IEC60950, 3
rd
edition).
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 hazardous voltages, including the
ac mains; and
■ One VI pin and one VO 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 safety 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 pin and ground.
The power module has extra-low voltage (ELV) outputs
when all inputs are ELV.
The input to these units is to be provided with a maxi-
mum 20 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
circuitry and can endure current limiting for an unlim-
ited duration. At the point of current-limit inception, the
unit shifts from voltage control to current control. If the
output 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.
Remote On/Off
To turn the power module on and off, the user must
supply a switch to control the voltage between the on/off
terminal and the V
I(–) terminal (Von/off). The switch can be
an open collector or equivalent (see Figure 17). A logic
low is V
on/off = 0 V to 1.2 V, during which the module is on.
The maximum I
on/off during a logic low is 1 mA. The switch
should maintain a logic-low voltage while sinking 1 mA.
During a logic high, the maximum V
on/off generated by
the power module is 15 V. The maximum allowable
leakage current of the switch at V
on/off = 15 V is 50 µA.
If not using the remote on/off feature, short the
ON/OFF pin to V
I(–).
8-580
Figure 17. Remote On/Off Implementation
+
Ion/off
Von/off
CASE
ON/OFF
V
I(+)
V
I(–)
SENSE(+)
SENSE(–)
V
O(+)
V
O(–)
–
