Datasheet

XTR300

www.ti.com

SBOS336C –JUNE 2005– REVISED JUNE 2011

POWER DISSIPATION

Power dissipation depends on power supply, signal, and load conditions. It is dominated by the power dissipation

of the output transistors of the OPA. For dc signals, power dissipation is equal to the product of output current,

OUT

and the output voltage across the conducting output transistor (V

– V

OUT

It is very important to note that the temperature protection does not shut the part down in overtemperature

conditions, unless the EF

pin is connected to the output enable pin OD; see the Driver Output Disable section.

The power that can be safely dissipated in the package is related to the ambient temperature and the heatsink

design and conditions. The QFN package with an exposed thermal pad is specifically designed to provide

excellent power dissipation, but board layout greatly influences the heat dissipation.

To appropriately determine the required heatsink area, required power dissipation should be calculated and the

relationship between power dissipation and thermal resistance should be considered to minimize overheat

conditions and allow for reliable long-term operation.

The heat sinking efficiency can be tested using the EF

output signal. This output goes low at nominally +140°C

junction temperature (assume 6% tolerance). With full power dissipation (for example, maximum current into a

0Ω load), the ambient temperature can be slowly raised until the OT flag goes low. This flag would indicate the

minimum heat-sinking for the usable operation condition.

The recommended landing pattern for the QFN package is shown at the end of this data sheet.