Page 14

March 2001 TOKO, Inc.

TK715xxAS

REVERSE VOLTAGE PROTECTION

The internal reverse bias protection eliminates the require-

ment for a reverse voltage protection diode. This saves

both cost and board space.

Another reverse voltage protection technique is illustrated

below. The extra diode and extra capacitor are not neces-

sary with the TK715xxA. The high output voltage accuracy

is maintained because the diode forward voltage varia-

tions over temperature and load current have been elimi-

nated.

PARALLEL OPERATION

The series resistor R is put in the input line of the low output

voltage regulator in order to prevent overdissipation. The

voltage dropped across the resistor reduces the large

input-to-output voltage across the regulator, reducing the

power dissipation in the device.

APPLICATION INFORMATION (CONT.)

SWITCHING OPERATION

Even though the input voltages or the output voltages are

different, the outputs of the TK715xxA regulators can be

connected together, and the output voltages switched. If

two or more TK715xxA regulators are turned ON simulta-

neously, the highest output voltage will be present.

CURRENT BOOST OPERATION

The output current can be increased by connecting an

external PNP transistor as shown below. The output

current capability depends upon the H

transistor. Note: The TK715xxA internal short circuit pro-

tection and thermal sensor do not protect the external

transistor.

715xxAS

VOUT

VIN

GND

TK715xxAS

VOUT

VIN

TK71550A

5 V

VIN

TK71530A

TK71520A

3 V

2 V

R

TK715xxA

VIN

VOUT

0.22 µF

150

Ω

VIN

3.3 µF

TK71530A

VIN

TK71528A

VIN

VOUT

3.0 OR 2.8 V