LW020AF datasheet(9/16 Pages) GE

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Lineage Power

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

VI(+). 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:

The input source is to be provided with reinforced

insulation from any other hazardous voltages, includ-

ing the ac mains.

One VI pin and one VO pin are to be grounded or

both the input and output pins are to be kept floating.

The input pins of the module are not operator acces-

sible.

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

VO, 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 VI(–) terminal (Von/off). The

switch can be an open collector or equivalent (see Fig-

ure 14). A logic low is Von/off = –0.7 V to 1.2 V. The max-

imum Ion/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 Von/off generated by

the power module is 6 V. The maximum allowable leak-

age current of the switch at Von/off = 6 V is 50 µA.

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