LTM4600 LINER [Linear Technology], LTM4600 Datasheet - Page 14

• Manufacturer Part Number: LTM4600
• Description: 10A High Effi ciency DC/DC ?Module
• Manufacturer: LINER [Linear Technology]

APPLICATIO S I FOR ATIO
LTM4600
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 LTM4600 modules can be paralleled to provide
higher than 10A output current. Figure 7 shows the neces-
sary interconnection between two paralleled modules. The
OPTI-LOOP™ current mode control ensures good current
sharing among modules to balance the thermal stress.
The new feedback equation for two or more LTM4600s
in parallel is:
where N is the number of LTM4600s in parallel.
OPTI-LOOP is a trademark of Linear Technology Corporation.
14
V
OUT
V
Figure 7. Parallel Two µModules with Load Sharing
IN
=
0 6
.
V
•
V
PGND
V
PGND
100
IN
IN
U
N
R
k
COMP V
COMP V
SET
+
LTM4600
LTM4600
R
U
SET
OSET
OSET
R
SET
SGND
SGND
V
V
OUT
OUT
W
4600 F07
V
(20A
OUT
U
MAX
)
Thermal Considerations and Output Current Derating
The power loss curves in Figures 8 and 13 can be used
in coordination with the load current derating curves in
Figures 9 to 12, and Figures 14 to 15 for calculating an
approximate θ
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
θ
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
between 6°C/W to 9°C/W. This equates to a total of 124°C
at the junction of the device.
Safety Considerations
The LTM4600 modules do not provide isolation from V
V
with a rating twice the maximum input current should be
provided to protect each unit from catastrophic failure.
JA
OUT
parameters are correlated to the measure values, and
. There is no internal fuse. If required, a slow blow fuse
JA
JA
for the noted conditions. These equivalent
for the module with various heatsink-
IN
4600fa
JC
to