Tyco Electronics Corp.

7

Data Sheet

May 1999

dc-dc Converter; 18 Vdc to 36 Vdc Input, 28 Vdc Output; 250 W

FC250R Power Module:

Test Configurations

8-203 (C).o

Note: Measure input reflected-ripple current with a simulated source

tery impedance. Measure current as shown above.

Figure 8. Input Reflected-Ripple Test Setup

8-683 (C).f

Note: All measurements are taken at the module terminals. When

socketing, place Kelvin connections at module terminals to

avoid measurement errors due to socket contact resistance.

Figure 9. Output Voltage and Efficiency

Measurement Test Setup

8-513 (C).n

Note: Use a 0.1 µF ceramic capacitor and a 330 µF aluminum or

tantalum capacitor. The 330 µF capacitor is needed for stability.

Scope measurement should be made using a BNC socket.

Position the load between 50 mm and 76 mm (2 in. and 3 in.)

from the module.

Figure 10. Peak-to-Peak Output Noise

Measurement Test Setup

Design Considerations

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 8, a 100 µF

electrolytic capacitor (ESR < 0.3

Ω 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.,

UL1950, CSA C22.2 No. 950-95, and VDE 0805

(EN60950, IEC950).

For the converter output to be considered meeting the

requirements of safety extra-low voltage (SELV), the

input must meet SELV requirements.

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 25 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.

TO OSCILLOSCOPE

12 µH

BATTERY

Cs 220 µF

ESR < 0.1

Ω

@ 20

°C, 100 kHz

100 µF

ESR < 0.3

Ω

@ 100 kHz

SENSE(+)

SENSE(–)

LOAD

CONTACT AND

DISTRIBUTION LOSSES

SUPPLY

CONTACT

RESISTANCE

η

()

()

--------------------------------------------------



 x 100

%

=

1.0 µF

RESISTIVE

LOAD

SCOPE

COPPER STRIP

330 µF