TS4274

5V/400mA Fixed Voltage

Ultra Low Dropout Voltage Regulator

3/6

Version: B13

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.

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.