dw025 Lineage Power, dw025 Datasheet - Page 13

• Manufacturer Part Number: dw025
• Description: Dw025 Dual Output-series Power Modules Dc-dc Converters
• Manufacturer: Lineage Power

Data Sheet
April 2008
Thermal Considerations
Basic Thermal Performance
The DW025-Series Dual Output Power Modules have a
separate power stage for each of the outputs. This
means that the maximum operating temperature can
be predicted quite closely by treating each output indi-
vidually and then summing the results. Figures 16
through 21 are used to predict the safe operating con-
dition for many different operating and environmental
conditions.
The method used to determine the maximum ambient
temperature at a given air velocity is a four-step pro-
cess.
1. Find the power dissipated for output 1 by using the
2. Repeat step 1 for output 2 using Figures 16 through
3. Find the total power dissipated by summing the
4. Use the total power dissipated with Figure 20 to
For example, the DW025AF-M power module operating
at full load on both outputs with 54 V input has a power
dissipation of 3.6 W (from Figure 17) plus 3.1 W (from
Figure 16) for a total of 6.7 W. Using Figure 20, it can
be determined that the maximum ambient temperature
at natural convection that the DW025AF-M can operate
at is approximately 56 °C.
Keep in mind that these are approximations of the tem-
peratures and airflows required to keep the case tem-
perature below its maximum rating. The maximum case
temperature at the point shown in Figure 15 must be
kept at 100 °C or less.
Lineage Power
appropriate chart (Figures 16 through 19) for a par-
ticular output condition (I
19.
power dissipated on each of the outputs:
(P
determine the maximum ambient temperature at dif-
ferent air velocities.
DOUT1
+ P
DOUT2
) = P
D
total
O1
).
DW025 Dual Output-Series Power Modules: dc-dc Converters;
(continued)
36 Vdc to 75 Vdc Input; Dual Outputs; 25 W
Air Velocity
The air velocity required to maintain a desired maxi-
mum case temperature for a given power dissipation
and ambient temperature can be calculated using
Figure 21 and the following equation:
where
ent air (°C/W), T
temperature (°C), T
(°C), and P
module (W).
For example, to maintain a maximum case temperature
of 85 °C with an ambient inlet temperature of 55 °C and
a power dissipation of 6.7 W, the thermal resistance is:
This corresponds to an air velocity greater than
0.46 ms
CA
–1
(90 fpm) in Figure 21.
is the thermal resistance from case-to-ambi-
D
total is the total power dissipated from the
CA
C, max
85 °C 55 °C
------------------------------------
A
CA
is the ambient inlet temperature
6.7 W
is the desired maximum case
=
–
T
------------------------------- -
C max
P
,
D
total
–
= 4.5 °C/W
T
A
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