ltm4612 Linear Technology Corporation, ltm4612 Datasheet - Page 15

• Manufacturer Part Number: ltm4612
• Description: Ultralow Noise 36vin, 15vout, 5a, Dc/dc ?module
• Manufacturer: Linear Technology Corporation

tion. When the cooling is limited, proper output current
derating is necessary, considering ambient temperature,
airfl ow, input/output condition, and the need for increased
reliability.
The power loss curves in Figures 9 and 10 can be used
in coordination with the load current derating curves in
Figures 11 to 16 for calculating an approximate θ
the module. Graph designation delineates between no
heat sink, and a BGA heat sink. Each of the load current
derating curves will lower the maximum load current as a
function of the increased ambient temperature to keep the
maximum junction temperature of the power module at
APPLICATIONS INFORMATION
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
6
4
3
2
1
0
5
25
0
35
Figure 9. Power Loss at
12V
Figure 12. BGA Heat Sink
with 36V
36V
AMBIENT TEMPERATURE (°C)
1
OUT
45
IN
TO 15V
LOAD CURRENT (A)
0LFM
and 15V
55
IN
2
LFM
200
to 5V
OUT
65
24V
OUT
OUT
IN
3
75
TO 12V
400LFM
85
4
OUT
95
4612 F12
4612 F09
105
5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
6
4
3
2
0
0
5
1
0
25
Figure 10. Power Loss at 5V
35
Figure 13. No Heat Sink
with 24V
JA
AMBIENT TEMPERATURE (°C)
1
45
0LFM
for
LOAD CURRENT (A)
36V
LFM
55
200
2
IN
IN
TO 5V
65
to 12V
125°C maximum. This will maintain the maximum operat-
ing temperature below 125°C. Each of the derating curves
and the power loss curve that corresponds to the correct
output voltage can be used to solve for the approximate
θ
taken at three different air fl ow conditions. Each of the
derating curves in Figures 11 to 16 can be used with the
appropriate power loss curve in either Figure 9 or Figure
10 to derive an approximate θ
proximate θ
of the thermal characteristics is provided in the thermal
application note, AN110.
JA
3
OUT
75
of the condition. Each fi gure has three curves that are
OUT
400LFM
85
4
95
OUT
4612 F13
JA
4612 F10
105
for Figures 11 to 16. A complete explanation
5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0
25
25
35
35
Figure 14. BGA Heat Sink
with 24V
JA
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
Figure 11. No Heat Sink
with 36V
45
. Table 3 provides the ap-
45
0LFM
0LFM
55
LFM
55
200
IN
LFM
200
IN
to 12V
LTM4612
65
65
to 5V
75
75
OUT
OUT
400LFM
400LFM
85
85
15
95
95
4612 F14
4612 F11
4612f
105
105