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1

2

3

4

5

0.1

1

10

100

No Air Flow

150 LFM

250 LFM

SOT223 Power Dissipation

P

(3.3 * 2.5) V x 1 A + 800 mW

(9)

RθJAmax + (125 * 55)°C 800 mW + 87.5°C W

(10)

TPS72501

TPS72515, TPS72516

TPS72518, TPS72525

SLVS341D – MAY 2002 – REVISED MARCH 2004

THERMAL INFORMATION (continued)

From the data in Figure 23 and rearranging Equation 6, the maximum power dissipation for a different ground

plane area and a specific ambient temperature can be computed.

Figure 23. Maximum Power Dissipation vs Copper Heatsink Area

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:

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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