LTM4601 datasheet(14/24 Pages) LINER

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LTM4600

4600fc

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 θJA for the module with various heatsink-

ing methods. Thermal models are derived from several

Figure 7. Parallel Two μModules with Load Sharing

VIN

VOUT

VIN

VOUT

(20AMAX)

4600 F07

LTM4600

PGND

SGND

COMP VOSET

RSET

VIN

VOUT

LTM4600

PGND

SGND

COMP VOSET

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 θJA for the noted conditions. These equivalent

θJA parameters are correlated to the measured values, and

improve with air-ﬂow. 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 θJC

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 VIN to

VOUT. 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.

Table 4. 3.3V Output

DERATING CURVE

VIN (V)

POWER LOSS CURVE

AIR FLOW (LFM)

HEATSINK

θJA (°C/W)

Figure 14

Figure 13

None

15.2

Figure 14

Figure 13

200

None

14.6

Figure 14

Figure 13

400

None

13.4

Figure 15

Figure 13

BGA Heatsink

13.9

Figure 15

Figure 13

200

BGA Heatsink

11.1

Figure 15

Figure 13

400

BGA Heatsink

10.5

Table 3. 1.5V Output

DERATING CURVE

VIN (V)

POWER LOSS CURVE

AIR FLOW (LFM)

HEATSINK

θJA (°C/W)

Figures 9, 11

5, 12

Figure 8

None

15.2

Figures 9, 11

5, 12

Figure 8

200

None

Figures 9, 11

5, 12

Figure 8

400

None

Figures 10, 12

5, 12

Figure 8

BGA Heatsink

13.9

Figures 10, 12

5, 12

Figure 8

200

BGA Heatsink

11.3

Figures 10, 12

5, 12

Figure 8

400

BGA Heatsink

10.25

APPLICATIONS INFORMATION

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