
10
Tyco Electronics Corp
Data Sheet
July 1999
dc-dc Converters; 36 to 75 Vdc Input, 5 Vdc Output; 50 W to 150 W
JW050A, JW075A, JW100A, JW150A 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 
(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 meet-
ing the requirements of safety extra-low voltage 
(SELV), all of the following must be true:
I
The input source is to be provided with reinforced 
insulation from any hazardous voltages, including the 
ac mains.
I
One V
the input and output pins are to be kept floating. 
I
 pin and one V
O
 pin are to be grounded or both 
I
The input pins of the module are not operator acces-
sible.
I
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 tai-
lout characteristics (output current decrease or 
increase). The unit operates normally once the output 
current is brought back into its specified range.
Remote On/Off 
Two remote on/off options are available. Positive logic 
remote on/off turns the module on during a logic-high 
voltage on the ON/OFF pin, and off during a logic low. 
Negative logic remote on/off turns the module off dur-
ing a logic high and on during a logic low. Negative 
logic (code suffix “1”) is the factory-preferred configura-
tion.
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 (V
switch can be an open collector or equivalent (see 
Figure 20). A logic low is V
maximum I
on/off
 during a logic low is 1 mA. The switch 
should maintain a logic-low voltage while sinking 1 mA.
on/off
). The 
on/off
 = 0 V to 1.2 V. The 
During a logic high, the maximum V
the power module is 15 V. The maximum allowable 
leakage current of the switch at V
on/off
 generated by 
on/off
 = 15 V is 50 μA.
If not using the remote on/off feature, do one of the 
following:
For negative logic, short ON/OFF pin to V
For positive logic, leave ON/OFF pin open.
I
I
(–).
I
8-720 (C).c
Figure 20. Remote On/Off Implementation
SENSE(+)
V
O
(+)
SENSE(–)
V
O
(–)
V
I
(–)
+
–
I
on/off
ON/OFF
V
I
(+)
LOAD
V
on/off