JFC075C datasheet(14/20 Pages) MACOM

14 / 20 page

Data Sheet

October 1999

Tyco Electronics Corp.

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

JFC050C, JFC075C, JFC100C Power Modules:

Thermal Considerations (continued)

Introduction (continued)

For additional information regarding this module, refer to

the

Thermal Management JC-, JFC-, JW-, and JFW-

Series 50 W to 150 W Board-Mounted Power Modules

Technical Note (TN97-008EPS).

Heat Transfer Without Heat Sinks

Increasing airflow over the module enhances the heat

transfer via convection. Figure 19 shows the maximum

power that can be dissipated by the module without

exceeding the maximum case temperature versus local

ambient temperature (TA) for natural convection

through 4 m/s (800 ft./min.).

Note that the natural convection condition was mea-

sured at 0.05 m/s to 0.1 m/s (10 ft./min. to 20 ft./min.);

however, systems in which this power module may be

used typically generate a natural convection airflow

rate of 0.3 m/s (60 ft./min.) due to other heat dissipating

components in the system. The use of Figure 19 is

shown in the following example.

Example

What is the minimum airflow necessary for a JFC100C

operating at VI = 28 V, an output current of 6.7 A, and a

maximum ambient temperature of 40 °C?

Solution

Given: VI = 28 V

IO = 6.7 A

TA = 40 °C

Determine PD (Use Figure 21.):

PD = 15.5 W

Determine airflow (v) (Use Figure 19.):

v = 1.75 m/s (350 ft./min.)

8-1150 (C).a

Figure 19. Forced Convection Power Derating with

No Heat Sink; Either Orientation

8-1782 (C)

Figure 20. JFC050C Power Dissipation vs. Output

Current at 25 °C

102030

100

LOCAL AMBIENT TEMPERATURE, TA (˚C)

4.0 m/s(800 ft./min.)

0.1 m/s (NAT. CONV.)

(20 ft./min.)

0.5 m/s(100 ft./min.)

1.0 m/s(200 ft./min.)

1.5 m/s(300 ft./min.)

2.0 m/s(400 ft./min.)

2.5 m/s(500 ft./min.)

3.0 m/s(600 ft./min.)

3.5 m/s(700 ft./min.)

1.0

1.5

2.0

2.5

3.0

OUTPUT CURRENT, IO (A)

0.0

0.5

VI = 36 V

VI = 28 V

VI = 18 V

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