ADP2370ACPZ-5.0-R7 datasheet(29/32 Pages) AD

29 / 32 page

Data Sheet

ADP2370/ADP2371

Rev. A | Page 29 of 32

THERMAL CONSIDERATIONS

In most applications, the ADP2370/ADP2371 do not dissipate

much heat due to their high efficiency. However, in applications

with high ambient temperature and high supply voltage-to-output

voltage differential, the heat dissipated in the package may be

large enough to cause the junction temperature of the die to

exceed the 125°C maximum.

If the junction temperature of the ADP2370/ADP2371 exceeds

150°C, the regulator enters thermal shutdown. The regulator

recovers only after the junction temperature has fallen below

130°C, this helps to prevent any permanent damage to the IC.

Thermal analysis for the chosen application is clearly very

important to guarantee reliable operation under all conditions.

The junction temperature of the die is the sum of the ambient

temperature of the environment and the temperature rise of the

package due to the power dissipation, as shown in Equation 2.

To guarantee reliable operation, the junction temperature of the

ADP2370/ADP2371 must not exceed 125°C. To ensure the junc-

tion temperature stays below this maximum value, the user must

be aware of the parameters that contribute to junction temperature

changes. These parameters include ambient temperature, power

dissipation in the power device, and the thermal resistance between

the junction and ambient air (θJA). The θJA number is dependent

on the package assembly compounds that are used and the amount

of PCB copper soldered to the package GND and EPAD. Table 8

shows typical θJA values of the 8-lead, 3 mm × 3 mm LFCSP for

various PCB copper sizes.

Table 8. Typical θJA Values

Copper Size (mm2)

θJA (°C/W)

251

162.2

100

124.1

500

68.7

1000

56.5

6400

42.4

1 The device is soldered to minimum size pin traces.

The junction temperature of the ADP2370/ADP2371 is

calculated from the following equation:

TJ = TA + (PD × θJA)

(2)

where:

TA is the ambient temperature.

PD is the total power dissipation in the die, given by

PD = PBUCK = PSW + PTRAN + PSW_COND

(3)

where:

PSW, PTRAN, and PSW_COND are defined in the Efficiency section.

For a given ambient temperature and total power dissipation,

there exists a minimum copper size requirement for the PCB to

ensure the junction temperature does not rise above 125°C. The

following figures (Figure 86 to Figure 89) show junction

temperature calculations for different ambient temperatures,

total power dissipation, and areas of PCB copper.

105

115

125

135

145

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

TOTAL POWER DISSIPATION (W)

6400mm2

500mm2

100mm2

TJ MAX

Figure 86. Junction Temperature vs. Power Dissipation, TA = 25°C

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

TOTAL POWER DISSIPATION (W)

100

110

120

130

140

6400mm2

500mm2

100mm2

TJ MAX

Figure 87. Junction Temperature vs. Power Dissipation, TA = 50°C

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

TOTAL POWER DISSIPATION (W)

6400mm2

500mm2

100mm2

TJ MAX

105

115

125

135

145

Figure 88. Junction Temperature vs. Power Dissipation, TA = 65°C

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