Data Sheet
JHC/JHW350 Power Module; dc-dc Converter
March 26, 2008
18 – 36Vdc or 36 – 75Vdc Input; 28Vdc Output; 350W
versus local ambient temperature (TA) for natural
convection through 2m/s (400 ft./min).
Thermal Considerations
The power modules operate in a variety of thermal
environments; however, sufficient cooling should be
provided to help ensure reliable operation of the unit.
Heat-dissipating components inside the unit are
thermally coupled to the case. Heat is removed by
conduction, convection, and radiation to the
surrounding environment. Proper cooling can be
verified by measuring the case temperature. Peak
temperature (TC) occurs at the position indicated in
Figure 20.
Note that the natural convection condition was
measured at 0.05 m/s to 0.1 m/s (10ft./min. to 20
ft./min.); however, systems in which these power
modules may be used typically generate natural
convection airflow rates of 0.3 m/s (60 ft./min.) due to
other heat dissipating components in the system. The
use of Figure 21 is shown in the following example:
Example
What is the minimum case temperature must be
maintained to operate a JHW350R at Vin = 48 V, an
output power of 300W in longitudinal orientation.
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.
Solution:
Given: VI = 48V
Po = 300W
Determine case temperature (Use Figure 21):
TC = 92 °C
For reliable operation this temperature should not
exceed 100ºC threshold.
MEASURE CASE
TEMPERATURE HERE (Tc)
400
350
300
250
200
150
100
50
VI(+)
VO(+)
+ SEN
TRIM
ON/OFF
CASE
VI(-)
- SEN
30.5
(1.20)
20 30
40 50
60 70
80 90 100 110
VO(-)
CASE TEMPERATURE, TC (°C)
29.0
Figure 21. Output Power Derating for JHC/JHW350R
(Vo = 28V) in Longitudinal Orientation; Airflow
Direction From Vin(–) to Vout(--); Vin = Vin, nom
(1.14)
Figure 20. Metal Case (Tc ) Temperature
Measurement Location (top view).
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 Tc temperature of the power
modules is 100 °C, you can limit this temperature to a
lower value for extremely high reliability.
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.
Heat Transfer via Convection
Increased airflow over the module enhances the heat
transfer via convection. Following derating figures
shows the maximum output power that can be
delivered by each module in the respective orientation
without exceeding the maximum TC temperature
LINEAGE POWER.
12
LINEAGEPOWER [ LINEAGE POWER CORPORATION ]
