LP3891ES-1.5 National Semiconductor, LP3891ES-1.5 Datasheet - Page 9

• Manufacturer Part Number: LP3891ES-1.5
• Description: 0.8A Fast-Response Ultra Low Dropout Linear
• Manufacturer: National Semiconductor

Application Hints
HEATSINKING TO-220 PACKAGE
The thermal resistance of a TO220 package can be reduced
by attaching it to a heat sink or a copper plane on a PC
board. If a copper plane is to be used, the values of θ
be same as shown in next section for TO263 package.
The heatsink to be used in the application should have a
heatsink to ambient thermal resistance,
θ
In this equation, θ
to the surface of the heat sink and θ
tance from the junction to the surface of the case. θ
about 3˚C/W for a TO220 package. The value for θ
pends on method of attachment, insulator, etc. θ
between 1.5˚C/W to 2.5˚C/W. If the exact value is unknown,
2˚C/W can be assumed.
HEATSINKING TO-263 PACKAGE
The TO-263 package uses the copper plane on the PCB as
a heatsink. The tab of these packages are soldered to the
copper plane for heat sinking. The graph below shows a
curve for the θ
HA
≤ θ
JA
− θ
CH
JA
− θ
of TO-263 package for different copper area
CH
JC
is the thermal resistance from the case
.
(Continued)
JC
is the thermal resis-
CH
CH
varies
JA
JC
de-
will
is
9
sizes, using a typical PCB with 1 ounce copper and no solder
mask over the copper area for heat sinking.
FIGURE 1. θ
JA
vs Copper (1 Ounce) Area for TO-263
package
20069525
www.national.com