Datasheet

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TO-263 Power Dissipation
P
D
max +
(
3.3 * 2.5
)
V 3A + 2.4W
(9)
R
QJA
max +
(
125 * 55
)
°C
2.4W
+ 29°CńW
(10)
15
20
25
30
35
40
0 0.01 0.1 1 10 100
Copper Heatsink Area − cm
2
− Thermal Resistance −
θJA
R C/W
°
No Air Flow
150 LFM
250 LFM
TPS75801 , , TPS758A01
TPS75815 , TPS75818
TPS75825 , TPS75833
SLVS330F – JUNE 2001 – REVISED APRIL 2007
THERMAL INFORMATION (continued)
The TO-263 package provides an effective means of managing power dissipation in surface-mount applications.
The TO-263 package dimensions are provided in the mechanical drawings at the end of the data sheet. The
addition of a copper plane directly underneath the TO-263 package enhances the thermal performance of the
package.
To illustrate, the TPS75825 in a TO-263 package was chosen. For this example, the average input voltage is
3.3V, the average output voltage is 2.5V, the average output current is 3A, the ambient temperature +55 ° C, the
air flow is 150 LFM, and the operating environment is the same as documented below. Neglecting the quiescent
current, the maximum average power is:
Substituting T
J
max for T
J
in Equation 6 results in Equation 10 :
From Figure 26 , R
Θ JA
vs Copper Heatsink Area, the ground plane needs to be 2cm
2
for the part to dissipate
2.4W. The model operating environment used in the computer model to construct Figure 26 consisted of a
standard JEDEC High-K board (2S2P) with a 1-ounce internal copper plane and ground plane. The package is
soldered to a 2-ounce copper pad. The pad is tied through thermal vias to the 1-ounce ground plane. Figure 27
shows the side view of the operating environment used in the computer model.
Figure 26. Thermal Resistance vs Copper Heatsink Area
16
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