TPS78223 Datasheet, PDF (11/20 Pages) Texas Instruments – 150mA, Ultra-Low Quiescent Current, IQ 1mA Low-Dropout Linear Regulator

TPS782xx
www.ti.com ........................................................................................................................................... SBVS115A – AUGUST 2008 – REVISED SEPTEMBER 2008
THERMAL INFORMATION
THERMAL PROTECTION
Thermal protection disables the device output when
the junction temperature rises to approximately
+160°C, allowing the device to cool. Once the
junction temperature cools to approximately +140°C,
the output circuitry is enabled. Depending on power
dissipation, thermal resistance, and ambient
temperature, the thermal protection circuit may cycle
on and off again. This cycling limits the dissipation of
the regulator, protecting it from damage as a result of
overheating.
Any tendency to activate the thermal protection circuit
indicates excessive power dissipation or an
inadequate heatsink. For reliable operation, junction
temperature should be limited to +125°C maximum.
To estimate the margin of safety in a complete design
(including heatsink), increase the ambient
temperature until the thermal protection is triggered;
use worst-case loads and signal conditions. For good
reliability, thermal protection should trigger at least
+35°C above the maximum expected ambient
condition of your particular application. This
configuration produces a worst-case junction
temperature of +125°C at the highest expected
ambient temperature and worst-case load.
The internal protection circuitry of the TPS782 series
has been designed to protect against overload
conditions. However, it is not intended to replace
proper heatsinking. Continuously running the TPS782
series into thermal shutdown degrades device
reliability.
POWER DISSIPATION
The ability to remove heat from the die is different for
each package type, presenting different
considerations in the PCB layout. The PCB area
around the device that is free of other components
moves the heat from the device to the ambient air.
Performance data for JEDEC low- and high-K boards
are given in the Dissipation Ratings table. Using
heavier copper increases the effectiveness in
removing heat from the device. The addition of plated
through-holes to heat-dissipating layers also
improves the heatsink effectiveness. Power
dissipation depends on input voltage and load
conditions. Power dissipation (P_D) is equal to the
product of the output current times the voltage drop
across the output pass element (V_IN to V_OUT), as
shown in Equation 2:
P_D = (V_IN - V_OUT) ´ I_OUT
(2)
PACKAGE MOUNTING
Solder pad footprint recommendations for the
TPS782 series are available from the Texas
Instruments web site at www.ti.com through the
TPS782 series product folders.
Copyright © 2008, Texas Instruments Incorporated
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