Datasheet

− Maximum Junction Temperature − 125
T
JM
C
°
1
2
3
4
5
0.1 1 10 100
− Maximum Power Dissipation − W
P
D
Copper Heatsink Area − cm
2
T
A
= 55°C
No Air Flow
150 LFM
250 LFM
P
D
max +
(
3.3 * 2.5
)
V x 1 A + 800 mW
R
θJA
max + (125 * 55)°Cń800 mW + 87.5°CńW
TPS72501
TPS72515, TPS72516
TPS72518, TPS72525
SLVS341E –MAY 2002–REVISED JUNE 2010 www.ti.com
Figure 23. Maximum Power Dissipation vs Copper Heatsink Area
SOT223 Power Dissipation
The SOT223 package provides an effective means of managing power dissipation in surface mount applications.
The SOT223 package dimensions are provided in the Mechanical Data section at the end of the data sheet. The
addition of a copper plane directly underneath the SOT223 package enhances the thermal performance of the
package.
To illustrate, the TPS72525 in a SOT223 package was chosen. For this example, the average input voltage is
3.3 V, the output voltage is 2.5 V, the average output current is 1 A, the ambient temperature 55°C, no air flow is
present, and the operating environment is the same as documented below. Neglecting the quiescent current, the
maximum average power is:
(9)
Substituting T
J
max for T
J
into Equation 6 gives Equation 10:
(10)
From Figure 24, R
ΘJA
vs PCB Copper Area, the ground plane needs to be 0.55 in
2
for the part to dissipate 800
mW. The operating environment used to construct Figure 24 consisted of a board with 1 oz. copper planes. The
package is soldered to a 1 oz. copper pad on the top of the board. The pad is tied through thermal vias to the 1
oz. ground plane.
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