TS2938

500mA Ultra Low Dropout Voltage Regulator

with Inhibit Function

3/6

Version: E11

Application Circuit

Application Information

Application

The TS2938 series is a high performance with low dropout voltage regulator suitable for moderate to high current

and voltage regulator application. Its 500Mv (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 TS2938 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 TS2938 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 6.8uF 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 provide 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 TS2938 series is specified between finite loads. If the output current is too small leakage currents dominate

and the output voltage rises. A 5mA 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.

Fixed Output Voltage Type