TS5201_1 Datasheet, PDF (5/6 Pages) Taiwan Semiconductor Company, Ltd – 200mA Low Noise LDO Voltage Regulator with Enable

Application Information (continues)
Thermal Characteristics
TS5201 series is designed to provide 200mA 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
TS5201CX533 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 200mA, the maximum input voltage can be
determined. Formt eh electrical characteristics table,
the maximum ground current for 200mA output current
is 2.5mA.
445mW = ( Vin – 3.3V ) * 200mA + Vin * 2.5mA
445mW = Vin * 200mA – 3.3 * 200mA + Vin * 2.5mA
445mW = Vin * 200mA – 495mW + Vin * 2.5mA
950mW = Vin * 152.5mA
Vin(max) = 6.23v
Therefore, a 3.3V application at 200mA of output
current can accept a maximum input voltage of 6.23V
in a SOT-25 package.
Noise Reduction Capacitors
On adjustable devices, a capacitor from ADJ to GND
will decrease high frequency noise on the output. See
following figure
Minimum Load
The TS5201 will remain stable and in regulation
with no load unlike many other voltage regulators.
This is especially important in CMOS RAM
keep-alive applications.
Dual-Supply Systems
When used in dual supply systems where the
regulator load is returned to a negative supply, the
output voltage must be diode clamped to ground.
TS5201 series
5-6
2005/08 rev. C