Datasheet

. Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator

LP2954, LP2954A

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SNVS096D –JUNE 1999–REVISED MARCH 2013

Typical Performance Characteristics (continued)

Short-Circuit Output

Current and Maximum Maximum Power Dissipation

Output Current (DDPAK/TO-263)

(1)

Figure 21. Figure 22.

(1) The maximum allowable power dissipation is a function of the maximum junction temperature, T

(MAX), the junction-to-ambient thermal

resistance, θ

J-A

, and the ambient temperature, T

. The maximum allowable power dissipation at any ambient temperature is calculated

using:

will go into thermal shutdown. The junction-to-ambient thermal resistance of the TO-220 (without heatsink) is 60°C/W, 73°C/W for the

DDPAK/TO-263, and 160°C/W for the SOIC-8. If the DDPAK/TO-263 package is used, the thermal resistance can be reduced by

increasing the P.C. board copper area thermally connected to the package: Using 0.5 square inches of copper area, θ

is 50°C/W; with

1 square inch of copper area, θ

is 37°C/W; and with 1.6 or more square inches of copper area, θ

is 32°C/W. The junction-to-case

thermal resistance is 3°C/W. If an external heatsink is used, the effective junction-to-ambient thermal resistance is the sum of the

junction-to-case resistance (3°C/W), the specified thermal resistance of the heatsink selected, and the thermal resistance of the interface

between the heatsink and the LP2954. Some typical values are listed for interface materials used with TO-220:

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