TPPM0301

400-mA LOW-DROPOUT REGULATOR

WITH AUXILIARY POWER MANAGEMENT

SLVS315 – SEPTEMBER 2000

5

POST OFFICE BOX 655303

THERMAL INFORMATION

To ensure reliable operation of the device, the junction temperature of the output device must be within the safe

operating area (SOA). This is achieved by having a means to dissipate the heat generated from the junction

of the output structure. There are two components that contribute to thermal resistance. They consist of two

The ability to efficiently dissipate the heat from the junction is a function of the package style and board layout

incorporated in the application. The operating junction temperature is determined by the operating ambient

This particular application uses the enhanced 8-pin SO package with an integral fused lead frame (terminals

5 to 8). By incorporating a dedicated heat spreading copper plane of at least two square inches on a double-side

Alternatively, if no dedicated copper plane is incorporated for this device and the PCB has a multilayer

construction, the ground terminals (5 to 8) could be electrically connected to the ground plane of the board. This

will provide a means for heat spreading through the copper plane associated within the PCB (GND layer). This

Hence, maximum power dissipation allowable for an operating ambient temperature of 70

°C, and a maximum

junction temperature of 150

°C is determined as:

Using two square inches of dedicated copper plane on double-sided PCB,

Using a multilayer board and utilizing the ground plane for heat spreading, worst case maximum power

dissipation is determined by:

Normal operating maximum power dissipation is (see Figure 1):