UC621XXG-AF5-R(2014) 查看數據表（PDF） - Unisonic Technologies

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UC621XXG-AF5-R
(Rev.:2014)

BOOSTING VOLTAGE REGULATORS

Unisonic Technologies 

UC621XX

 TYPICAL APPLICATION CIRCUIT

CMOS IC

 OPERATIONAL EXPLANATION

Functional Description

Output voltage (VOUT) can be fixed by revising the external transistor's base current. This can be done by

comparing the detected voltage level and the set voltage power supply level.

 DIRECTIONS FOR USE

Suggestions for External Comporients

1. PNP Transistor

The selection of a transistor should take into account output current, input voltage and power dissipation for each

specific application. It is recommended that a transistor that has a low output saturated voltage (VCE) and high hFE

characteristics be used.

2. RB Resistor

Although the IC unit is protected by a base current remitter circuit, it is recommended that a resistor (RB) be

connected between the transistor's base and the IC's EXT pin to protect the transistor.

Required output current can be calculated using the following equation although characteristic variations and

conditions of use should be carefully checked before use. The following equation also indicates the conditions

needed to obtain IOUT (max.) at VIN (min.). However, the larger the input current, the larger the output current (IOUT) that

can be obtained.

VIN(MIN) -1.2(V)

RB

0.7(V)

RBE

IOUT(MAX)

hFE

3. RBE Resistor, CL Capacitor

To prevent oscillation due to output load variation, use of a phase compensation capacitor CL is recommended.

Please use a Tantalum capacitor of at least 10μF. Please also use an RBE resistor of less than 47kΩ.

An RBE resistor of between 20kΩ and 47kΩ is recommended for less power consumption.

4. Input Impedance

In order to control oscillation brought about as a result of impedance at the power supply line, connect a capacitor

of 10μF or more (Tantalum) between the external transistor's emitter and the ground pin.

Special Note

1. Protection Circuit

The built-in protect circuit is to protect the IC only. Therefore to prevent output shorts and overshoot current

through the transistor, use of a resistor RB or an overshoot current protection circuit is recommended. Care should

also be taken with the transistor's power dissipation.

UNISONIC TECHNOLOGIES CO., LTD

www.unisonic.com.tw

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