Lineage Power 9
Data Sheet
April 2008
36 Vdc to 75 Vdc Inputs; 20 W
LW020 Single-Output-Series Power Modules:
Design Considerations
Grounding Considerations
For standard units, the case is connected internally to
V
I(+). For units with the case ground pin option, the
case is not connected internally allowing the user flexi-
bility in grounding.
Input Source Impedance
The power module should be connected to a low ac-
impedance input source. Highly inductive source
impedances can affect the stability of the power mod-
ule. For the test configuration in Figure 11, a 33 µF
electrolytic capacitor (ESR < 0.7 ¾ at 100 kHz)
mounted close to the power module helps ensure sta-
bility of the unit. For other highly inductive source
impedances, consult the factory for further application
guidelines.
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:
n The input source is to be provided with reinforced
insulation from any other hazardous voltages, includ-
ing the ac mains.
n One VI pin and one VO pin are to be grounded or
both the input and output pins are to be kept floating.
n The input pins of the module are not operator acces-
sible.
n 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 pins 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 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
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.
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 protection circuit has a higher voltage
set point than the primary loop (see Feature Specifica-
tions table). In a fault condition, the overvoltage clamp
ensures that the output voltage does not exceed
V
O, clamp, max. This provides a redundant voltage-control
that reduces the risk of output overvoltage.
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 REMOTE ON/OFF pin, and off during a
logic low. Negative logic remote on/off, device code
suffix “1,” turns the module off during a logic high and
on during a logic low.
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 Fig-
ure 14). A logic low is V
on/off = –0.7 V to 1.2 V. The max-
imum 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 6 V. The maximum allowable leak-
age current of the switch at V
on/off = 6 V is 50 µA.
