DS_L36SA12004_10252013

11

THERMAL CONSIDERATIONS

Thermal management is an important part of the system

design. To ensure proper, reliable operation, sufficient

cooling of the power module is needed over the entire

temperature range of the module. Convection cooling is

usually the dominant mode of heat transfer.

Hence, the choice of equipment to characterize the

thermal performance of the power module is a wind

tunnel.

Thermal Testing Setup

Delta’s DC/DC power modules are characterized in

heated vertical wind tunnels that simulate the thermal

environments

encountered

in

most

electronics

equipment. This type of equipment commonly uses

vertically mounted circuit cards in cabinet racks in which

the power modules are mounted.

The

following

figure

shows

the

wind

tunnel

characterization setup. The power module is mounted

on a test PWB and is vertically positioned within the

wind tunnel. The space between the neighboring PWB

and the top of the power module is constantly kept at

6.35mm (0.25’’).

Note: Wind Tunnel Test Setup Figure Dimensions are in millimeters and (Inches)

12.7 (0.5”)

MODULE

AIR FLOW

50.8 (2.0”)

FACING PWB

PWB

AIR VELOCITY

AND AMBIENT

TEMPERATURE

MEASURED BELOW

THE MODULE

Figure 20: Wind tunnel test setup

Thermal Derating

Heat can be removed by increasing airflow over the module.

To enhance system reliability, the power module should

always

be

operated

below

the

maximum

operating

temperature. If the temperature exceeds the maximum

module temperature, reliability of the unit may be affected.

THERMAL CURVES

Figure 21: Hot spot temperature measured point

＊

The allowed maximum hot spot temperature is defined at 130

℃

L36SA12004(standard) Output Current vs. Ambient Temperature and Air Velocity

@Vin = 48V (Either Orientation)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

30

35

40

45

50

55

60

65

70

75

80

85

Natural

Convection

200LFM

400LFM

300LFM

100LFM

Output Current (A)

Ambient Temperature (℃)

500LFM

Figure 22: Output current vs. ambient temperature and air velocity