TK11120S データシートの表示（PDF） - Toko America Inc

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TK11120S

VOLTAGE REGULATOR WITH ON/OFF SWITCH

Toko America Inc  

TK111xxS

DEFINITION AND EXPLANATION OF TECHNICAL TERMS (CONT.)

Reverse Voltage Protection

ON/OFF RESPONSE WITH CONTROL

Reverse voltage protection prevents damage due to the

output voltage being higher than the input voltage. This

fault condition can occur when the output capacitor remains

charged and the input is reduced to zero, or when an

external voltage higher than the input voltage is applied to

the output side.

REDUCTION OF OUTPUT NOISE

The turn-on time depends upon the value of the output

capacitor and the noise bypass capacitor. The turn-on time

will increase with the value of either capacitor. The graphs

below show the relationship between turn-on time and

load capacitance. If the value of these capacitors is reduced,

the load and line regulation will suffer and the noise voltage

will increase. If the value of these capacitors is increased,

the turn-on time will increase.

Although the architecture of the Toko regulators is designed

to minimize semiconductor noise, further reduction can be

achieved by the selection of external components. The

obvious solution is to increase the size of the output

capacitor. A more effective solution would be to add a

capacitor to the noise bypass terminal. The value of this

capacitor should be 0.1 µF or higher (higher values provide

greater noise reduction). Although stable operation is

possible without the noise bypass capacitor, this terminal

has a high impedance and care should be taken to avoid

a large circuit area on the printed circuit board when the

capacitor is not used. Please note that several parameters

are affected by the value of the capacitors and bench

testing is recommended when deviating from standard

values.

OUTPUT VOLTAGE RESPONSE B

(OFF→ON)

ILOAD = 30 mA, CL = 2.2 µF

CN = 0.1 µF

CN = 0.33 µF

CN = 0.47 µF

CN = 0.68µF

CN = 1.0 µF

CONTROL FUNCTION

The TK111xxS has an active high control pin. The control

pin requires over 1.8 V for operation and under 0.6 V for

standby. For the range of 0.6 V < VCONT < 1.8 V, operation

is undefined. If the control function is not used, connect the

control pin to VIN.

VIN

0

2

4

6

8

TIME (ms)

OUTPUT VOLTAGE RESPONSE A

(OFF→ON)

ILOAD = 30 mA, CN = 3300 pF

CL = 0.68 µF

CL = 0.47µF

SW

CL = 1.5 µF

CL = 1.0 µF

Page 10

CN

CONTROL FUNCTION

-5

5 15 25 35 45

TIME (µs)

March 1999 TOKO, Inc.

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