JFC075C datasheet(13/20 Pages) MACOM

13 / 20 page

Tyco Electronics Corp.

Data Sheet

October 1999

dc-dc Converters; 18 to 36 Vdc Input, 15 Vdc Output; 50 W to 100 W

JFC050C, JFC075C, JFC100C Power Modules:

Feature Descriptions (continued)

Output Current Monitor

The current monitor (CURMON) pin produces a dc volt-

age proportional to the dc output current of the module.

The voltage is referenced to the secondary SENSE(–)

pin and is typically 4.8 V at rated output current. For

paralleling with Fx300x modules, consult the factory for

the V/A ratio. The output impedance of this pin is

approximately 20 k¾, so customer detection circuitry

must have a high-impedance input.

Overtemperature Protection

To provide protection in a fault condition, the unit is

equipped with a thermal shutdown circuit. The shut-

down circuit will not engage unless the unit is operated

above the maximum case temperature. Recovery for

the thermal shutdown is accomplished by cycling the

dc input power off for at least 1.0 second or by toggling

the primary or secondary referenced remote on/off sig-

nal for at least 1.0 second.

Power Good Signal

The power good signal (PWRGOOD pin) is an open-

collector, secondary-referenced pin that is pulled low

when all five of the following conditions are met:

The sensed output voltage is greater than half the

rated nominal output voltage.

The overvoltage shutdown latch is not set.

The thermal shutdown latch is not set.

The unit is not in current limit.

Secondary internal bias is present.

There is one situation where the power good signal can

be low even though the module has failed. This can

occur when the module is paralleled with other mod-

ules for additional output power (i.e., the output ORing

diodes would not be used). If one module power train

stops delivering power (fails), the other paralleled mod-

ule(s) would provide a voltage at the output pin of the

failed module. The failed module would then not detect

that its output power was not being delivered. However,

in this situation the current monitor pins of the paral-

leled modules would indicate that current is not being

delivered from one module and that module had failed.

For redundant applications, the ORing diodes would

keep the other module voltages from being applied to

the failed module output and the power good signal

would indicate a failure.

Thermal Warning

The thermal warning (TEMPWARN) pin is a second-

ary-referenced, open-collector output that shorts to

SENSE(–) a few degrees before the module goes into

thermal shutdown. When the module temperature

cools, the thermal warning pin will open, but the unit

will remain latched off until the input power or the pri-

mary or secondary referenced remote on/off is recy-

cled for 1.0 second.

Thermal Considerations

Introduction

The JFC-Series power modules operate in a variety of

thermal environments; however, sufficient cooling

should be provided to help ensure reliable operation of

the units. Heat-dissipating components inside the units

are thermally coupled to the case. Heat is removed by

conduction, convection, and radiation to the surround-

ing environment. Proper cooling can be verified by

measuring the case temperature. Peak temperature

(TC) occurs at the position indicated in Figure 18.

8-1397 (C).a

Note: Top view, measurements shown in millimeters and (inches).

Pin locations are for reference.

Figure 18. Case Temperature Measurement

Location

The temperature at this location should not exceed

100 °C. The output power of the module should not

exceed the rated power for the module as listed in the

Ordering Information table.

Although the maximum case temperature of the power

modules is 100 °C, you can limit this temperature to a

lower value for extremely high reliability.

7.6 (0.30)

38.0 (1.50)

MEASURE CASE

TEMPERATURE HERE

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