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LW025F

LW025 Single-Output-Series Power Modules: 36 Vdc to 75 Vdc Inputs; 25 W

Tyco Electronics 

Advance Data Sheet

March 1999

Feature Descriptions (continued)

Remote On/Off (continued)

LW025 Single-Output-Series Power Modules:

36 Vdc to 75 Vdc Inputs; 25 W

-

Von/off

+

Ion/off

VI(+)

VI(-)

REMOTE

ON/OFF

Figure 13. Remote On/Off Implementation

8-758(C).a

Output Voltage Adjustment

Output voltage trim allows the user to increase or decrease the output voltage set point of a module. This is accom-

plished by connecting an external resistor between the TRIM pin and either the VO(+) or VO(–) pins. With an exter-

nal resistor between the TRIM and VO(+) pins (Radj-down), the output voltage set point (VO, adj) decreases. With an

external resistor between the TRIM pin and VO(–) pin (Radj-up), VO, adj increases.

The following equations determine the required external resistor value to obtain an output voltage change of ý%:

Radj-down = c----[--d-----⋅---(---1---∆-–---%--∆----%------)---–-----1----] – b kΩ

Radj-up =

-------a--------- – b kΩ

d ⋅ ∆%

Device

a

b

c

d

LW025F

14.0

51.1

5.2

2.7

LW025A

4.02

16.9

2.01

2.0

–5% VO Radj-down

111.7 k¾

19.3 k¾

+5% VO Radj-up

52.7 k¾

23.3 k¾

The adjusted output voltage cannot exceed 110% of the nominal output voltage between the VO(+) and VO(–) ter-

minal.

The modules have a fixed current-limit set point. Therefore, as the output voltage is adjusted down, the available

output power is reduced. In addition, the minimum output current is a function of the output voltage. As the output

voltage is adjusted down, the minimum required output current can increase.

Output Overvoltage Protection

The output overvoltage clamp consists of control circuitry, independent of the primary regulation loop, that monitors

the voltage on the output terminals. The control loop of the protection circuit has a higher voltage set point than the

primary loop (see Feature Specifications 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.

Tyco Electronics Corp.

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