LTM4615 datasheet(20/32 Pages) LINER

20 / 32 page

LTM4639

4639f

For more information www.linear.com/LTM4639

Figure 8. 3.3V Input Power Loss Curves

Figure 9. 5V Input Power Loss Curves

APPLICATIONS INFORMATION

Figure 10. 7V Input Power Loss Curves

temperature loss from the 7V to 1.0V power loss curve at

17A, and the 1.4 multiplying factor at 120°C junction. If the

80°C ambient temperature is subtracted from the 120°C

junction temperature, then the difference of 40°C divided

by 4.2W equals a 9.5°C/W θJA thermal resistance. Table

2 specifies a 10°C/W value which is very close. Table 2

through Table 4 provides equivalent thermal resistances

for 1.0V, 2.5V and 5V outputs with and without airflow and

heat sinking. The derived thermal resistances in Tables 2

thru 4 for the various conditions can be multiplied by the

calculatedpowerlossasafunctionofambienttemperature

to derive temperature rise above ambient, thus maximum

junction temperature. Room temperature power loss

can be derived from the efficiency curves in the Typical

Performance Characteristics section and adjusted with

the above ambient temperature multiplicative factors. The

printed circuit board is a 1.6mm thick four layer board with

two ounce copper for the two outer layers and one ounce

copper for the two inner layers. The PCB dimensions are

95mm × 76mm. The BGA heat sinks are listed in Table 6.

OUTPUT CURRENT (A)

2.5

3.0

3.5

4639 F08

2.0

1.5

8 10

1.0

0.5

5.0

4.5

4.0

3.3V TO 1.8V POWER LOSS

3.3V TO 1.5V POWER LOSS

3.3V TO 1.2V POWER LOSS

3.3V TO 1V POWER LOSS

OUTPUT CURRENT (A)

2.5

3.0

3.5

4639 F09

2.0

1.5

8 10

1.0

0.5

5.0

4.5

4.0

5V TO 3.3V POWER LOSS

5V TO 2.5V POWER LOSS

5V TO 1.8V POWER LOSS

5V TO 1.5V POWER LOSS

5V TO 1.2V POWER LOSS

5V TO 1V POWER LOSS

OUTPUT CURRENT (A)

2.5

3.0

3.5

4639 F10

2.0

1.5

8 10

1.0

0.5

5.0

4.5

4.0

7V TO 5V POWER LOSS

7V TO 3.3V POWER LOSS

7V TO 2.5V POWER LOSS

7V TO 1.8V POWER LOSS

7V TO 1.5V POWER LOSS

7V TO 1.2V POWER LOSS

7V TO 1V POWER LOSS

Figure 11. 5VIN to 1.0VOUT No Heat Sink

Figure 13. 7VIN to 1.0VOUT No Heat Sink

Figure 12. 5VIN to 1.0VOUT with Heat Sink

TEMPERATURE (°C)

120

4639 F11

100

0 LFM

200 LFM

400 LFM

TEMPERATURE (°C)

140

4639 F13

100 120

0 LFM

200 LFM

400 LFM

TEMPERATURE (°C)

140

4639 F12

100 120

0 LFM

200 LFM

400 LFM

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