TPS65281, TPS65281-1

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SLVSBH7B – JULY 2012 – REVISED DECEMBER 2012

APPLICATION INORMATION

Thermal Shutdown

The device implements an internal thermal shutdown to protect itself if the junction temperature exceeds 160°C.

The thermal shutdown forces the buck converter to stop switching when the junction temperature exceeds

thermal trip threshold. Once the die temperature decreases below 140°C, the device reinitiates the power up

sequence. The thermal shutdown hysteresis is 20°C.

Power Dissipation and Junction Temperature

The total power dissipation inside TPS65281/TPS65281-1 should not exceed the maximum allowable junction

temperature of 125°C. The maximum allowable power dissipation is a function of the thermal resistance of the

package,

temperature based on the power dissipation in the package. However, it is important to note that thermal analysis

is strongly dependent on additional system level factors. Such factors include air flow, board layout, copper

thickness and surface area, and proximity to other devices dissipating power. Good thermal design practice must

include all system level factors in addition to individual component analysis.

To calculate the temperature inside the device under continuous load, use the following procedure.

1. Define the total continuous current through the buck converter (including the load current through power

switches). Make sure the continuous current does not exceed the maximum load current requirement.

2. From the graphs below, determine the expected losses (Y axis) in Watts for the buck converter inside the

the data is measured in the provided evaluation board (EVM).

Electrical Characteristics table.

4. The power loss through power switches can be calculated by:

(18)

5. The Dissipating Rating Table provides the thermal resistance,

6. The maximum temperature inside the IC can be calculated by:

(19)

Where:

Figure 32. Buck Power Loss vs Output Current

Figure 33. Buck Power Loss vs Output Current

Copyright © 2012, Texas Instruments Incorporated

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Product Folder Links: TPS65281 TPS65281-1