LTM4630IV View Datasheet(PDF) - Linear Technology
Part Name
Description
Manufacturer
LTM4630IV Datasheet PDF : 34 Pages
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LTM4630
APPLICATIONS INFORMATION
value is shown in the Pin Configuration section and should
accurately equal the θJA value because approximately
100% of power loss flows from the junction through the
board into ambient with no airflow or top mounted heat
sink. Each system has its own thermal characteristics,
therefore thermal analysis must be performed by the user
in a particular system.
The LTM4630 module has been designed to effectively
remove heat from both the top and bottom of the pack-
age. The bottom substrate material has very low thermal
resistance to the printed circuit board. An external heat
sink can be applied to the top of the device for excellent
heat sinking with airflow.
Figures 10 and 11 show temperature plots of the LTM4630
with no heat sink and 200LFM airflow.
These plots equate to a paralleled 12V to 1.0V at 36A
design operating at 84.5% efficiency, and 12V to 1.2V at
36A design operating at 86% efficiency.
Safety Considerations
The LTM4630 modules do not provide isolation from VIN
to VOUT. There is no internal fuse. If required, a slow blow
fuse with a rating twice the maximum input current needs
to be provided to protect each unit from catastrophic
failure. The device does support over current protection.
A temperature diode is provided for monitoring internal
temperature, and can be used to detect the need for thermal
shutdown that can be done by controlling the RUN pin.
Power Derating
The 1.0V and 1.5V power loss curves in Figures 13 and 14
can be used in coordination with the load current derating
curves in Figures 15 to 22 for calculating an approximate
ΘJA thermal resistance for the LTM4630 with various heat
sinking and airflow conditions. The power loss curves are
taken at room temperature, and are increased with a 1.35
to 1.4 multiplicative factor at 125°C. These factors come
from the fact that the power loss of the regulator increases
about 45% from 25°C to 150°C, thus a 50% spread over
125°C delta equates to ~0.35%/°C loss increase. A 125°C
maximum junction minus 25°C room temperature equates
to a 100°C increase. This 100°C increase multiplied by
0.35%/°C equals a 35% power loss increase at the 125°C
junction, thus the 1.35 multiplier.
The derating curves are plotted with CH1 and CH2 in
parallel single output operation starting at 36A of load
with low ambient temperature. The output voltages are
1.0V and 1.5V. These are chosen to include the lower and
higher output voltage ranges for correlating the thermal
resistance. Thermal models are derived from several
temperature measurements in a controlled temperature
chamber along with thermal modeling analysis.
Figure 11. Thermal Image 12V to 1.2V,
36A with 200LFM without Heat Sink
Figure 10. Thermal Image 12V to 1.0V,
36A with 200LFM without Heat Sink
For more information www.linear.com/LTM4630
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