LP38853EVAL National Semiconductor, LP38853EVAL Datasheet - Page 14

• Manufacturer Part Number: LP38853EVAL
• Description: BOARD EVALUATION LP38853
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LP38853EVAL

• Channels Per Ic: 1 - Single
• Voltage - Output: 1.2V
• Current - Output: 3A
• Voltage - Input: 3 ~ 5.5V
• Regulator Type: Positive Adjustable
• Operating Temperature: -40°C ~ 125°C
• Board Type: Fully Populated
• Utilized Ic / Part: LP38853
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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For this equation, θ
The value for θ
tor, etc. θ
heat-sink manufacturer datasheet for details and recommen-
dations.
Heat-Sinking The TO-263 Package
The TO-263 package has a θ
rating of 3°C/W. These ratings are for the package only, no
additional heat-sinking, and with no airflow.
The TO-263 package uses the copper plane on the PCB as
a heat-sink. The tab of this package is soldered to the copper
plane for heat sinking. Figure 3 shows a curve for the θ
TO-263 package for different copper area sizes, using a typ-
ical PCB with 1 ounce copper and no solder mask over the
copper area for heat-sinking.
Figure 3 shows that increasing the copper area beyond 1
square inch produces very little improvement. The minimum
value for θ
32°C/W.
Figure 4 shows the maximum allowable power dissipation for
TO-263 packages for different ambient temperatures, assum-
FIGURE 3. θ
FIGURE 4. Maximum Power Dissipation vs Ambient
CH
Temperature for the TO-263 Package
JA
varies between 1.5°C/W to 2.5°C/W. Consult the
JA
for the TO-263 package mounted to a PCB is
CH
vs Copper (1 Ounce) Area for the TO-263
depends on method of attachment, insula-
JC
is about 3°C/W for a TO-220 package.
package
JA
rating of 60°C/W, and a θ
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JA
JC
of
14
ing θ
125°C.
Heat-Sinking The PSOP-8 Package
The LP38853MR package has a θ
a θ
the device DAP soldered to an area of 0.008 square inches
(0.09 in x 0.09 in) of 1 ounce copper, with no airflow.
Increasing the copper area soldered to the DAP to 1 square
inch of 1 ounce copper, using a dog-bone type layout, will
improve the θ
creasing the copper area beyond 1 square inch produces very
little improvement.
Figure 6 shows the maximum allowable power dissipation for
the PSOP-8 package for a range of ambient temperatures,
assuming θ
ature is 125°C.
FIGURE 5. θ
FIGURE 6. Maximum Power Dissipation vs Ambient
JC
JA
rating of 11°C/W. The θ
is 35°C/W and the maximum junction temperature is
Temperature for the PSOP-8 Package
JA
JA
is 98°C/W and the maximum junction temper-
JA
vs Copper (1 Ounce) Area for the PSOP-8
rating to 98°C/W. Figure 5 shows that in-
Package
JA
rating of 168°C/W includes
JA
rating of 168°C/W, and
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