LT8613 datasheet(22/26 Pages) LINER

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LT8619/LT8619-5

8619f

For more information www.linear.com/LT8619

Figure 13. Case Temperature Rise vs Load Current

Figure 14. Case Temperature Rise vs Ambient Temperature

For higher ambient temperatures, care should be taken in

the layout of the PCB to ensure good heat sinking of the

LT8619. The exposed pad on the bottom of the package

must be soldered to a ground plane. This ground should

be tied to large copper layers below with thermal vias;

these layers will spread heat dissipated by the LT8619.

Placing additional vias can reduce thermal resistance fur-

ther. Figure 13 shows the rise in case temperature vs load

current. Note that a higher ambient temperature will result

in bigger case temperature rise as shown in Figure 14.

Power dissipation within the LT8619 can be estimated

by calculating the total power loss from an efficiency

measurement and subtracting the inductor loss. The

die temperature is calculated by multiplying the LT8619

power dissipation by the thermal resistance from junction

to ambient.

Figure 15 shows the typical derating maximum output

current curve. As with any monolithic switching regu-

lator, the PCB layout, thermal resistance, air flow, other

heat sources in the vicinity affect how efficiently heat can

be removed from the die and radically change the die

junction temperature. The actual LT8619 switcher output

voltage and current sourcing capability might deviate from

the performance curve stated in this data sheet. When

pushing the LT8619 to its limit, verify its operation in the

actual environment. AT HIGH AMBIENT TEMPERATURE,

CONTINUOUS OPERATION ABOVE THE MAXIMUM

OPERATION JUNCTION TEMPERATURE MAY IMPAIR

DEVICE RELIABILITY OR PERMANENTLY DAMAGE THE

DEVICE.

Figure 15. LT8619 Derating Maximum Output

Current with Junction Temperature Less Than 125°C

APPLICATIONS INFORMATION

VIN = 12V

VOUT = 5V

fSW = 700kHz

TA = 25°C

FORCED CONTINUOUS MODE

LOAD CURRENT (A)

0.2

0.4

0.6

0.8

1.0

1.2

8619 F13

VIN = 12V

VOUT = 5V, 1.2A LOAD

fSW = 700kHz

CONTINUOUS OPERATION ABOVE

MAXIMUM JUNCTION TEMPERATURE

MAY PERMANENTLY DAMAGE THE DEVICE

AMBIENT TEMPERATURE (°C)

100

125

8619 F14

VIN = 12V

VOUT = 3.3V

TJ(MAX) ≤ 125°C

FORCED CONTINUOUS MODE

AMBIENT TEMPERATURE (°C)

100 105 110 115 120 125

0.2

0.4

0.6

0.8

1.0

1.2

1.4

8619 F15

fSW = 700kHz

fSW = 2MHz

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