GE Industrial Solutions NaOS NXA025 SMT - Manual (Page 12)

Data Sheet
October 5, 2009 Naos TM NXA025 SMT Non-isolated Power Modules:
10 – 14Vdc Input; 0.8Vdc to 5.5Vdc Output; 25A output current
LINEAGE POWER 12
Thermal Considerations
The power modules operate in a variety of thermal
environments; however, sufficient cooling should be
provided to help ensure reliable operation.
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.
The thermal reference point, T
ref
used in the
specifications is shown in Figure 29. For reliable
operation this temperature should not exceed 110
o C.
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.
Tref
Tref
Figure 29. Tref Temperature measurement location.
Heat Transfer via Convection
Increased airflow over the module enhances the heat
transfer via convection. Derating figures showing the
maximum output current that can be delivered by various
module versus local ambient temperature (T
A
) for natural
convection and up to 2m/s (400 ft./min) are shown in the
respective Characteristics Curves section.
Base-Plate option (-H)
The baseplate option (-H) power modules are constructed
with baseplate on topside of the open frame power
module. The baseplate includes two through-threaded,
M3 x 0.5 mounting hole pattern, which enable heat sinks
or cold plates to attach to the module. The mounting
torque must not exceed 0.56 N-m (5 in.-lb.) during heat
sink assembly. The baseplate option allows customers to
operate the module in an extreme thermal environment
with attachment of heatsink/cold-plate for proper cooling
of internal component to heighten reliable and consistent
operation. The thermal reference point for baseplate
option is center of the heat plate on the top-side. For
reliable operation this temperature should not exceed
105
o C.
Layout Considerations
The input capacitors should be located equal distance
from the two input pins of the module. Recommended
layout is shown in the mechanical section. In addition to
the input and output planes, a ground plane beneath the
module is recommended.