tHermaL management

The mFW Series of dC/dC converters has an upper operating

temperature of + 85°C at the baseplate of the case. The degree of

heat sinking required to remain within this limit may be determined

from Figure 1 which shows the maximum allowed internal power dissi-

The efficiency for all combinations of PoUT and VIN for the various

models may be obtained from the graphs on the preceding pages.

Efficiency = 85% (From Figure 7)

From Figure 1 we can see that this situation will require thermal resis-

tance of approximately 4.5°C / watt.

Conversely we may also find the maximum ambient temperature

which can be tolerated if we know the heat sink thermal resistance.

thermalResistance=3°C/watt.

Efficiency = 83.5% (From Figure 3)

From Figure 1 we can see that the maximum allowed ambient temper-

ature is approximately 75°C.

An mFW Series converter in still air (other than convective currents)

and with no conductive cooling paths other than through electrical

connections at the pins will exhibit a thermal resistance of approxi-

mately 4°C / watt. In cases where this value proves to be too high it is

recommended that additional heat sinking be supplied. The simplest

method of accomplishing this is to firmly attach the converter to a PCB

thereby providing a conductive thermal path. Secondly it is recom-

mended that airflow be provided over the converter. Although each

situation requires a thorough thermal analysis these two measures

can reduce the thermal resistance to as low as 2°C / watt. If calcula-

tions indicate further heat sinking is required it is recommended that

additional thermal mass be provided either under the base plate or on

top of the converter’s mounting flanges or both.

Degrees Centigrade

20

° 40° 60° 80° 100° 120° 140°

20

15

10

5

U=4

°C/

W

U=

3°C/

W

U=

2°C/

W

U=0

°C/

W

Internal Power Dissipation (max)

vs. Ambient Temperature

pin Out

See case L for dimensions.

pin dual Output

triple Output

1

Positive Input

Positive Input

2

Case Ground

Case Ground

3

Input Common

Input Common

4

Inhibit/Sync In

Inhibit/Sync In

5

Negative output

Neg. Aux. output

6

Positive output

Positive Aux. output

7, 8 output Common

output Common

9, 10 No Connection

main (+5) output

Squared corner indicates pin one.

BOTTOM VIEW

MFW

1

2

3

4

5

6

7

8

9

10

mFwSeRIeS

70 WATT

Page 4 of 7

mFwRevF20100212

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