LTM4602HV
14
4602hvf
APPLICATIO S I FOR ATIO
WUU
U
approximate θ
JA
for the module with various heatsink-
ing methods. Thermal models are derived from several
temperature measurements at the bench, and thermal
modeling analysis. Application Note 103 provides a detailed
explanation of the analysis for the thermal models, and the
derating curves. Tables 3 and 4 provide a summary of the
equivalent θ
JA
for the noted conditions. These equivalent
θ
JA
parameters are correlated to the measure values, and
improved with air-fl ow. The case temperature is maintained
at 100°C or below for the derating curves. This allows for
4W maximum power dissipation in the total module with
top and bottom heatsinking, and 2W power dissipation
through the top of the module with an approximate θ
JC
between 6°C/W to 9°C/W. This equates to a total of 124°C
at the junction of the device. The θ
JA
values in Tables 3
and 4 can be used to derive the derating curves for other
output voltages.
Safety Considerations
The LTM4602HV modules do not provide isolation from
V
IN
to V
OUT
. There is no internal fuse. If required, a slow
blow fuse with a rating twice the maximum input current
should be provided to protect each unit from catastrophic
failure.
In the application where the light load effi ciency is im-
portant, tying the FCB pin above 0.6V threshold enables
discontinuous operation where the bottom MOSFET turns
off when inductor current reverses. Therefore, the conduc-
tion loss is minimized and light load effi cient is improved.
The penalty is that the controller may skip cycle and the
output voltage ripple increases at light load.
Paralleling Operation with Load Sharing
Two or more LTM4602HV modules can be paralleled to
provide higher than 6A output current. Figure 7 shows
the necessary interconnection between two paralleled
modules. The OPTI-LOOP™ current mode control en-
sures good current sharing among modules to balance
the thermal stress. The new feedback equation for two or
more LTM4602HVs in parallel is:
VV
k
N
R
R
OUT
SET
SET
=
+
06
100
.•
where N is the number of LTM4602HVs in parallel.
Thermal Considerations and Output Current Derating
The power loss curves in Figures 8 and 15 can be used
in coordination with the load current derating curves in
Figures 9 to 14, and Figures 16 to 19 for calculating an
Figure 7. Parallel Two µModules with Load Sharing
OPTI-LOOP is a trademark of Linear Technology Corporation.
V
IN
100k
V
OUT
V
IN
V
OUT
12A MAX
4602HV F07
LTM4602HV
PGOOD
V
PULLUP
PGND SGNDCOMP V
OSET
R
SET
V
IN
PGOOD
V
OUT
LTM4602HV
PGND
SGNDCOMP V
OSET
