Technical Note

July 1996

250 W—300 W Board-Mounted Power Modules

Thermal Management for FC- and FW-Series

Tyco Electronics Power Systems, Inc.

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© 2001 Tyco Electronics Corporation, Harrisburg, PA. All International Rights Reserved.

Printed in U.S.A.

July 1996

TN96-009EPS

Printed on

Recycled Paper

Figures 11 and 12 can be used to determine thermal

performance under various airflow and heat sink con-

figurations as shown in the following examples.

Example 4: Airflow Required to Maintain Tc

Although the maximum case temperature for the FC-

and FW-Series 250 W—300 W BMPMs is 100 °C, one

may want to limit the maximum case temperature to a

lower value for extremely high reliability. If an 85 °C

case temperature is desired, what are the allowable

minimum airflow/heat sink combinations necessary for

a transverse mounted FW300A1 operating at 54 V

input line and an output current of 50 A with a maxi-

mum ambient of 40 °C?

Solution:

= (85 – 40) / 46

= 1.0 °C/W

Use Figure 12 to determine air velocity:

No heat sink:

v >> 600 ft./min.

1/4 in. heat sink:

v >> 600 ft./min.

1/2 in. heat sink:

v = 450 ft./min.

1 in. heat sink:

v = 260 ft./min.

1 1/2 in. heat sink:

v = 205 ft./min.

Example 5: Determining Tc

Suppose that there is an air velocity of 600 ft./min.

available for the configuration stated in Example 4.

What is the case temperature for the various heat sink

configurations?

Solution:

Tc = (

Using thermal resistances (

θ) from Figure 12:

No heat sink:

θ = 1.5 °C/W

Tc = (1.5 x 46) + 40 = 109 °C

1/4 in. heat sink:

θ = 1.2 °C/W

Tc = (1.2 x 46) + 40 = 95 °C

1/2 in. heat sink:

θ = 0.9 °C/W

Tc = (0.9 x 46) + 40 = 81 °C

1 in. heat sink:

θ = 0.6 °C/W

Tc = (0.6 x 46) + 40 = 68 °C

1 1/2 in. heat sink:

θ = 0.5 °C/W

Tc = (0.5 x 46) + 40 = 63 °C

In this configuration, the module would not operate

within the maximum case temperature of 100 °C unless

a heat sink was attached.

Thermal Shutdown

The FC- and FW-Series 250 W—300 W BMPMs has a

latching thermal shutdown circuit designed to turn off

the module if it is operated in excess of the maximum

case temperature. Recovery from thermal shutdown is

accomplished by cycling the dc input power off for at

least 1.0 s, or toggling the primary referenced ON/OFF

signal for at least 1.0 s.