TS5204_13 Datasheet, PDF (3/9 Pages) Taiwan Semiconductor Company, Ltd – 80mA Low Noise LDO Voltage Regulator

TS5204
80mA Low Noise LDO Voltage Regulator
Application Information
TS5204 series is designed to provide 80mA 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.
Θ_JA is layout dependent, the actual power dissipation of the regulator circuit can be determined using the
equation:
PD = (V_IN – V_OUT) * I_OUT + V_IN * I_GND
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 TS5204CX33 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
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 80mA, the
maximum input voltage can be determined. From the electrical characteristics table, the maximum ground
current for 80mA output current is 2.5mA.
445mW = (V_IN – 3.3V ) * 120mA + V_IN * 2.5mA
445mW = V_IN * 120mA – 3.3 * 120mA + V_IN * 2.5mA
445mW = V_IN * 120mA – 395mW + V_IN * 2.5mA
840mW = V_IN * 122.5mA
V_IN (max) = 6.85V
Therefore, a 3.3V application at 80mA of output current can accept a maximum input voltage of 6.85V in a SOT-
23 package.
Input Capacitor Requirement
An input capacitor of 0.1uF or greater is recommended when the device is more than 10” away from the bulk AC
supply capacitance or when the supply is a battery.
Output Capacitor Requirement
The TS5204 series requires an output capacitor to maintain stability and improve transient response is necessary.
2.2uF minimum is recommended. Larger values improve the regulator’s transient response. The output capacitor
value may be increased without limit.
The output capacitor should have an ESR (effective series resistance) less than 5Ω and a resonant frequency
above 1MHz. Ultra low ESR capacitors can cause a low amplitude oscillation on the output and/or under damped
transient response. Most of tantalum or aluminum electrolytic capacitors are adequate; film types will work. Since
many aluminum electrolytic have electrolytes that freeze at about –30^oC, solid tantalums are recommended for
operation below –25^oC. At lower values of output current, less output capacitance is required for output stability.
The capacitor can be reduced to 0.47uF for current below 10mA or 0.33uF for currents below 1mA.
No Load Stability
The TS5204 series 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 Operation
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.
3/9
Version: J13