P
D(MAX)
T
J(MAX)
T
A
R
JA
150°C
85°C
38.1 k W
1700 mW
=
–
θ
=
–
/
=
TPS61090, TPS61091, TPS61092
SLVS484C – JUNE 2003 – REVISED DECEMBER 2014
www.ti.com
12.3 Thermal Considerations
Implementation of integrated circuits in low-profile and fine-pitch surface-mount packages typically requires
special attention to power dissipation. Many system-dependent issues such as thermal coupling, airflow, added
heat sinks and convection surfaces, and the presence of other heat-generating components affect the power-
dissipation limits of a given component.
Three basic approaches for enhancing thermal performance are listed below.
•
Improving the power dissipation capability of the PCB design
•
Improving the thermal coupling of the component to the PCB
•
Introducing airflow in the system
The maximum junction temperature (T
J
) of the TPS6109x devices is 150°C. The thermal resistance of the 16-pin
QFN PowerPAD package (RSA) isR
Θ
JA
= 38.1 °C/W, if the PowerPAD is soldered and the board layout is
optimized. Specified regulator operation is assured to a maximum ambient temperature T
A
of 85°C. Therefore,
the maximum power dissipation is about 1700 mW. More power can be dissipated if the maximum ambient
temperature of the application is lower.
(9)
If designing for a lower junction temperature of 125°C, which is recommended, maximum heat dissipation is
lower. Using the above equation (8) results in 1050 mW power dissipation.
20
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