TS4274 Datasheet, PDF (3/10 Pages) Taiwan Semiconductor Company, Ltd – 400mA Ultra Low Dropout Fixed Voltage Regulator

TS4274
400mA Ultra Low Dropout Fixed Voltage Regulator
Application Information
The TS4274 series is a high performance with low dropout voltage regulator suitable for moderate to high current and
voltage regulator application. Its 600mV(typ) dropout voltage at full load and over temperature makes it especially
valuable in battery power systems and as high efficiency noise filters in post regulator applications. Unlike normal NPN
transistor design, where the base to emitter voltage drop and collector to emitter saturation voltage limit the minimum
dropout voltage, dropout performance of the PNP output of these devices is limited only by low Vce saturation voltage.
The TS4274 series is fully protected from damage due to fault conditions. Linear current limiting is provided. Output
current during overload conditions is constant. Thermal shutdown the device when the die temperature exceeds the
maximum safe operating temperature. Transient protection allows device survival even when the input voltage spikes
above and below nominal. The output structure of these regulators allows voltages in excess of the desired output
voltage to be applied without reverse current flow.
Typical Application Circuit
Output Capacitor
The TS4274 series requires an output capacitor to maintain stability and improve transient response. Proper capacitor
selection is important to ensure proper operation. The output capacitor selection is dependent upon the ESR of the
output capacitor the maintain stability. When the output capacitor is 10uF or greater, the output capacitor should have
an ESR less than 2 ohm. This will improve transient response as well as promoted stability. Ultra low ESR capacitors
(<100mohm), such as ceramic chip capacitors may promote instability. These very low ESR levels may cause an
oscillation and/or under damped transient response. A low ESR solid tantalum capacitor works extremely well and
provides good transient response and stability over temperature. Aluminum electrolytic can also be used, as long as
the ESR of the capacitor is <2ohm. The value of the output capacitor can be increased without limit. Higher
capacitance values help to improved transient response and ripple rejection and reduce output noise.
Minimum Load Current
The TS4274 series is specified between finite loads. If the output current is too small leakage currents dominate and
the output voltage rises. A 1mA minimum load current is necessary for proper regulation.
Input Capacitor
An input capacitor of 1uF or greater is recommended when the device is more that 4 inches away from the bulk AC
supply capacitance or when the supply is a battery. Small and surface mount ceramic chip capacitors can be used for
bypassing. Larger values will help to improve ripple rejection by bypassing the input to the regulator, further improving
the integrity of the output voltage.
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Version: A07