MHSL02555 Datasheet, PDF (1/8 Pages) General Semiconductor – Thermal Management for FC-and FW-Series 250W-300W Board-Mounted Power Modules

Technical Note
July 1996
Thermal Management for FC- and FW-Series
250 W—300 W Board-Mounted Power Modules
Introduction
Basic Thermal Management
Board-mounted power modules (BMPMs) enhance
the capabilities of advanced computer and communi-
cations systems by providing flexible power architec-
tures; however, proper cooling of the power modules
is required for reliable and consistent operation.
Maintaining the operating case temperature (Tc)
within the specified range keeps internal component
temperatures within their specifications. This, in turn,
helps keep the expected mean time between failures
(MTBF) from falling below the specified rating.
Tyco's FC- and FW- Series 250 W to 300 W BMPMs
are designed with high efficiency as a primary goal.
The 5 V output units have typical full load efficiencies
of 83%, which result in less heat dissipation and
lower operating temperatures. Also, these modules
use temperature resistant components, such as
ceramic capacitors, that do not exhibit wearout
behavior during prolonged exposure to high tempera-
tures, as do aluminum electrolytic capacitors.
This application note provides the necessary infor-
mation to verify that adequate cooling is present in a
given operating environment. This information is
applicable to all Tyco 250 W to 300 W BMPMs in the
4.6 in. x 2.4 in. x 0.5 in. package.
Proper cooling can be verified by measuring the case
temperature of the module (Tc) at the location indi-
cated in Figure 1. Note that the view in Figure 1 is of
the metal surface of the module (the pin locations
shown are for reference). Tc must not exceed 100 °C
while operating in the final system configuration.
After the module has reached thermal equilibrium,
the measurement can be made with a thermocouple
or surface probe. If a heat sink is mounted to the
case, make the measurement as close as possible to
the indicated position, taking into account the contact
resistance between the mounting surface and the
heat sink (see Heat Sink section).
1.20 (30.5)
VI(+)
VI(–)
ON/OFF
SYNC IN
SYNC OUT
CASE
MEASURE CASE
TEMPERATURE HERE
VO(+)
VO(–)
3.25 (82.6)
8-1303a
Figure 1. Case Temperature Measurement (Metal
Side)
While this is a valid method of checking for proper
thermal management, it it is only usable if the final
system configuration exists and can be used as a
test environment. The graphs on the accompanying
pages provide guidelines to predict the thermal per-
formance of the module for typical configurations that
include heat sinks in natural or forced airflow environ-
ments. However, due to differences between the test
setup and the final system environment, the module
case temperature must always be checked in the
final system configuration to verify proper operation.