tk71547as Toko Inc., tk71547as Datasheet - Page 14

• Manufacturer Part Number: tk71547as
• Description: Low Dropout Voltage Regulator
• Manufacturer: Toko Inc.

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.
TK715xxAS
Page 14
V IN
V IN
V IN
R
TK715xxAS
715xxAS
TK71550A
TK71530A
TK71520A
APPLICATION INFORMATION (CONT.)
GND
V OUT
V OUT
5 V
3 V
2 V
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.
V IN
V IN
V IN
150
0.22 µF
TK71530A
TK71528A
V IN
TK715xxA
March 2001 TOKO, Inc.
fe
of the external
3.0 OR 2.8 V
V OUT
3.3 µF
V OUT