TS5205_1 Datasheet, PDF (5/6 Pages) Taiwan Semiconductor Company, Ltd – 150mA Low Noise LDO Voltage Regulator with Enable

Application Information (continues)
Thermal Characteristics
TS5205 series is designed to provide 150mA of
continuous current in a very small package. Maximum
power dissipation can be calculated based on the
output current and the voltage drop across the part. To
determine the maximum power dissipation of the
package, use the junction-ambient thermal resistance
of the device and the following basic equation:
Pd(max) = [ Tj(max) – Ta ] /Θja
Tj(max) is the maximum junction temperature of the
die(125^oC), and Ta is the ambient operating
temperature. Θja is layout dependent, the actual
power dissipation of the regulator circuit can be
determined using the equation:
Pd = ( Vin – Vout ) * Iout + Vin * Ignd
Substituting Pd(max) for Pd and solving for the
operating conditions that are critical to the application
will give the maximum operating conditions for the
regulator circuit. For example, when operating the
TS5205CX533 at room temperature with a minimum
footprint layout, the maximum input voltage for a set
output current can be determined as follows:
Pd(max) = (125^oC – 25^oC) / 220^oC/W
Pd(max) = 455mW
The junction to ambient thermal resistance for the
minimum footprint is 220^oC/W, the maximum power
dissipation must not be exceeded for proper operation.
Using the output voltage of 3.3V and an output current
of 150mA, the maximum input voltage can be
determined. Formt eh electrical characteristics table,
the maximum ground current for 150mA output current
is 2.5mA.
445mW = ( Vin – 3.3V ) * 150mA + Vin * 2.5mA
445mW = Vin * 150mA – 3.3 * 150mA + Vin * 2.5mA
445mW = Vin * 150mA – 495mW + Vin * 2.5mA
950mW = Vin * 152.5mA
Vin(max) = 6.23v
Therefore, a 3.3V application at 150mA of output
current can accept a maximum input voltage of 6.23V
in a SOT-25 package.
Fixed Output Regulator Application
Ultra Low Noise Fixed Voltage Application
Includes a 470uF capacitor for low noise operation and
shows EN connected to IN for an application where
enable/shutdown is not required. Cout= 2.2uF
minimum.
Low Noise Fixed Voltage Application
An example of a low noise configuration where
Cbypass is not required. Cout= 1uF minimum
TS5205 series
5-6
2004/09 rev. B