Data Sheet
February 16, 2009
QSW025A0B Series Power Modules; DC-DC Converters
36 – 75Vdc Input; 12Vdc Output; 25A Output Current
temperature to a lower value for extremely high
reliability.
Feature Descriptions (continued)
Thermal Considerations
Please refer to the Application Note “Thermal
Characterization Process For Open-Frame Board-
Mounted Power Modules” for a detailed discussion of
thermal aspects including maximum device
temperatures.
The power modules operate in a variety of thermal
environments and sufficient cooling should be provided
to help ensure reliable operation.
Thermal considerations include ambient temperature,
airflow, module power dissipation, and the need for
increased reliability. A reduction in the operating
temperature of the module will result in an increase in
reliability. The thermal data presented here is based on
physical measurements taken in a wind tunnel.
Heat Transfer via Convection
Increased airflow over the module enhances the heat
transfer via convection. The thermal derating figures
(15-24) show the maximum output current that can be
delivered by each module in the respective orientation
without exceeding the maximum THx temperature
versus local ambient temperature (TA) for air flows of,
Natural Convection, 1 m/s (200 ft./min), 2 m/s (400
ft./min) and 3 m/s (600 ft./min).
Heat-dissipating components are mounted on the top
side of the module. Heat is removed by conduction,
convection and radiation to the surrounding environment.
Proper cooling can be verified by measuring the thermal
reference temperature (THx). Peak temperature (THx)
occurs at the position indicated in Figure 13. For reliable
operation this temperature should not exceed the listed
temperature threshold.
The use of Figures 15 - 24 are shown in the following
example:
Example
What is the minimum airflow necessary for a
QSW025A0B operating at VI = 48 V, an output current of
17A, and a maximum ambient temperature of 70 °C in
transverse orientation.
Solution:
Given: Vin= 48V, IO = 17A, TA = 70 °C
Determine required airflow (V) (Use Figure 15):
V = 1.5 m/sec. (300LFM) or greater.
TH1 and TH2 shall not exceed 125°C.
Figure 13. Location of the thermal reference
temperature TH.
TH3 shall not exceed 110°C.
Figure 14. Location of the thermal reference
temperature TH3 for Baseplate module.
The output power of the module should not exceed the
rated power for the module as listed in the Ordering
Information table.
Although the maximum THx temperature of the power
modules is 110 °C - 125 °C, you can limit this
LINEAGE POWER
9
LINEAGEPOWER [ LINEAGE POWER CORPORATION ]
